9.2. System Catalogs

The system catalogs are the place where a relational database management system stores schema metadata, such as information about tables and columns, and internal bookkeeping information. PostgreSQL’s system catalogs are regular tables. You can drop and recreate the tables, add columns, insert and update values, and severely mess up your system that way. Normally, one should not change the system catalogs by hand, there are normally SQL commands to do that. (For example, CREATE DATABASE inserts a row into the pg_database catalog — and actually creates the database on disk.) There are some exceptions for particularly esoteric operations, but many of those have been made available as SQL commands over time, and so the need for direct manipulation of the system catalogs is ever decreasing.

9.2.1. Overview

catalog-table lists the system catalogs. More detailed documentation of each catalog follows below.

Most system catalogs are copied from the template database during database creation and are thereafter database-specific. A few catalogs are physically shared across all databases in a cluster; these are noted in the descriptions of the individual catalogs.

System Catalogs

9.2.2. pg_aggregate

The catalog pg_aggregate stores information about aggregate functions. An aggregate function is a function that operates on a set of values (typically one column from each row that matches a query condition) and returns a single value computed from all these values. Typical aggregate functions are sum, count, and max. Each entry in pg_aggregate is an extension of an entry in linkend=»catalog-pg-proc»>**pg_proc**. The pg_proc entry carries the aggregate’s name, input and output data types, and other information that is similar to ordinary functions.

pg_aggregate Columns

Column Type Description
aggfnoid regproc (references linkend=»catalog-pg- proc»>pg_proc. oid) pg_proc OID of the aggregate function
aggkind char Aggregate kind: n for normal aggregates, o for ordered-set aggregates, or h for hypothetical-set aggregates
aggnumdirectargs int2 Number of direct (non-aggregated) arguments of an ordered-set or hypothetical-set aggregate, counting a variadic array as one argument. If equal to pronargs, the aggregate must be variadic and the variadic array describes the aggregated arguments as well as the final direct arguments. Always zero for normal aggregates.
aggtransfn regproc (references linkend=»catalog-pg- proc»>pg_proc. oid) Transition function
aggfinalfn regproc (references linkend=»catalog-pg- proc»>pg_proc. oid) Final function (zero if none)
aggcombinefn regproc (references linkend=»catalog-pg- proc»>pg_proc. oid) Combine function (zero if none)
aggserialfn regproc (references linkend=»catalog-pg- proc»>pg_proc. oid) Serialization function (zero if none)
aggdeserialfn regproc (references linkend=»catalog-pg- proc»>pg_proc. oid) Deserialization function (zero if none)
aggmtransfn regproc (references linkend=»catalog-pg- proc»>pg_proc. oid) Forward transition function for moving-aggregate mode (zero if none)
aggminvtransfn regproc (references linkend=»catalog-pg- proc»>pg_proc. oid) Inverse transition function for moving-aggregate mode (zero if none)
aggmfinalfn regproc (references linkend=»catalog-pg- proc»>pg_proc. oid) Final function for moving-aggregate mode (zero if none)
aggfinalextra bool True to pass extra dummy arguments to aggfinalfn
aggmfinalextra bool True to pass extra dummy arguments to aggmfinalfn
aggfinalmodify char Whether aggfinalfn modifies the transition state value: r if it is read-only, s if the aggtransfn cannot be applied after the aggfinalfn, or w if it writes on the value
aggmfinalmodify char Like aggfinalmodify, but for the aggmfinalfn
aggsortop oid (references linkend=»catalog-pg- operator»>pg_opera tor.oid) Associated sort operator (zero if none)
aggtranstype oid (references linkend=»catalog-pg- type»>pg_type. oid) Data type of the aggregate function’s internal transition (state) data
aggtransspace int4 Approximate average size (in bytes) of the transition state data, or zero to use a default estimate
aggmtranstype oid (references linkend=»catalog-pg- type»>pg_type. oid) Data type of the aggregate function’s internal transition (state) data for moving-aggregate mode (zero if none)
aggmtransspace int4 Approximate average size (in bytes) of the transition state data for moving-aggregate mode, or zero to use a default estimate
agginitval text The initial value of the transition state. This is a text field containing the initial value in its external string representation. If this field is null, the transition state value starts out null.
aggminitval text The initial value of the transition state for moving-aggregate mode. This is a text field containing the initial value in its external string representation. If this field is null, the transition state value starts out null.

New aggregate functions are registered with the linkend=»sql-createaggregate»>**CREATE AGGREGATE** command. See xaggr for more information about writing aggregate functions and the meaning of the transition functions, etc.

9.2.3. pg_am

The catalog pg_am stores information about relation access methods. There is one row for each access method supported by the system. Currently, only tables and indexes have access methods. The requirements for table and index access methods are discussed in detail in tableam and indexam respectively.

pg_am Columns

Column Type Description
oid oid Row identifier
amname name Name of the access method
amhandler regproc (references linkend=»catalog-pg- proc»>pg_proc. oid) OID of a handler function that is responsible for supplying information about the access method
amtype char t = table (including materialized views), i = index.

Примечание

Before PostgreSQL 9.6, pg_am contained many additional columns representing properties of index access methods. That data is now only directly visible at the C code level. However, pg_index_column_has_property() and related functions have been added to allow SQL queries to inspect index access method properties; see functions-info-catalog-table.

9.2.4. pg_amop

The catalog pg_amop stores information about operators associated with access method operator families. There is one row for each operator that is a member of an operator family. A family member can be either a search operator or an ordering operator. An operator can appear in more than one family, but cannot appear in more than one search position nor more than one ordering position within a family. (It is allowed, though unlikely, for an operator to be used for both search and ordering purposes.)

pg_amop Columns

Column Type Description
oid oid Row identifier
amopfamily oid (references linkend=»catalog-pg- opfamily»>pg_opfam ily.oid) The operator family this entry is for
amoplefttype oid (references linkend=»catalog-pg- type»>pg_type. oid) Left-hand input data type of operator
amoprighttype oid (references linkend=»catalog-pg- type»>pg_type. oid) Right-hand input data type of operator
amopstrategy int2 Operator strategy number
amoppurpose char Operator purpose, either s for search or o for ordering
amopopr oid (references linkend=»catalog-pg- operator»>pg_opera tor.oid) OID of the operator
amopmethod oid (references linkend=»catalog-pg- am»>pg_am.*oid *) Index access method operator family is for
amopsortfamily oid (references linkend=»catalog-pg- opfamily»>pg_opfam ily.oid) The B-tree operator family this entry sorts according to, if an ordering operator; zero if a search operator

A search operator entry indicates that an index of this operator family can be searched to find all rows satisfying WHERE indexed_column operator constant. Obviously, such an operator must return boolean, and its left-hand input type must match the index’s column data type.

An ordering operator entry indicates that an index of this operator family can be scanned to return rows in the order represented by ORDER BY indexed_column operator constant. Such an operator could return any sortable data type, though again its left-hand input type must match the index’s column data type. The exact semantics of the ORDER BY are specified by the amopsortfamily column, which must reference a B-tree operator family for the operator’s result type.

Примечание

At present, it’s assumed that the sort order for an ordering operator is the default for the referenced operator family, i.e., ASC NULLS LAST. This might someday be relaxed by adding additional columns to specify sort options explicitly.

An entry’s amopmethod must match the opfmethod of its containing operator family (including amopmethod here is an intentional denormalization of the catalog structure for performance reasons). Also, amoplefttype and amoprighttype must match the oprleft and oprright fields of the referenced linkend=»catalog-pg-operator»>**pg_operator** entry.

9.2.5. pg_amproc

The catalog pg_amproc stores information about support functions associated with access method operator families. There is one row for each support function belonging to an operator family.

pg_amproc Columns

Column Type Description
oid oid Row identifier
amprocfamily oid (references linkend=»catalog-pg- opfamily»>pg_opfam ily.oid) The operator family this entry is for
amproclefttype oid (references linkend=»catalog-pg- type»>pg_type. oid) Left-hand input data type of associated operator
amprocrighttype oid (references linkend=»catalog-pg- type»>pg_type. oid) Right-hand input data type of associated operator
amprocnum int2 Support function number
amproc regproc (references linkend=»catalog-pg- proc»>pg_proc. oid) OID of the function

The usual interpretation of the amproclefttype and amprocrighttype fields is that they identify the left and right input types of the operator(s) that a particular support function supports. For some access methods these match the input data type(s) of the support function itself, for others not. There is a notion of default support functions for an index, which are those with amproclefttype and amprocrighttype both equal to the index operator class’s opcintype.

9.2.6. pg_attrdef

The catalog pg_attrdef stores column default values. The main information about columns is stored in

linkend=»catalog-pg-attribute»>**pg_attribute**.

Only columns for which a default value has been explicitly set will have an entry here.

pg_attrdef Columns

Column Type Description
oid oid Row identifier
adrelid oid (references linkend=»catalog-pg- class»>pg_class. oid) The table this column belongs to
adnum int2 (references linkend=»catalog-pg- attribute»>pg_attr ibute.attnum) The number of the column
adbin pg_node_tree The column default value, in nodeToString() representation. Use pg_get_expr(adbin, adrelid) to convert it to an SQL expression.

9.2.7. pg_attribute

The catalog pg_attribute stores information about table columns. There will be exactly one pg_attribute row for every column in every table in the database. (There will also be attribute entries for indexes, and indeed all objects that have

linkend=»catalog-pg-class»>**pg_class**

entries.)

The term attribute is equivalent to column and is used for historical reasons.

pg_attribute Columns

Column Type Description
attrelid oid (references linkend=»catalog-pg- class»>pg_class. oid) The table this column belongs to
attname name The column name
atttypid oid (references linkend=»catalog-pg- type»>pg_type. oid) The data type of this column (zero for a dropped column)
attstattarget int4 attstattarget controls the level of detail of statistics accumulated for this column by linkend=»sql-analyze «>ANALYZE. A zero value indicates that no statistics should be collected. A negative value says to use the system default statistics target. The exact meaning of positive values is data type-dependent. For scalar data types, attstattarget is both the target number of most common values to collect, and the target number of histogram bins to create.
attlen int2 A copy of pg_type.typlen of this column’s type
attnum int2 The number of the column. Ordinary columns are numbered from 1 up. System columns, such as ctid, have (arbitrary) negative numbers.
attndims int4 Number of dimensions, if the column is an array type; otherwise 0. (Presently, the number of dimensions of an array is not enforced, so any nonzero value effectively means it’s an array.)
attcacheoff int4 Always -1 in storage, but when loaded into a row descriptor in memory this might be updated to cache the offset of the attribute within the row
atttypmod int4 atttypmod records type-specific data supplied at table creation time (for example, the maximum length of a varchar column). It is passed to type-specific input functions and length coercion functions. The value will generally be -1 for types that do not need atttypmod.
attbyval bool A copy of pg_type.typbyval of this column’s type
attalign char A copy of pg_type.typalign of this column’s type
attstorage char Normally a copy of pg_type.typstorage of this column’s type. For TOAST-able data types, this can be altered after column creation to control storage policy.
attcompression char The current compression method of the column. Typically this is „0“ to specify use of the current default setting (see guc-default-toast-co mpression). Otherwise, „p“ selects pglz compression, while „l“ selects LZ4 compression. However, this field is ignored whenever attstorage does not allow compression.
attnotnull bool This represents a not-null constraint.
atthasdef bool This column has a default expression or generation expression, in which case there will be a corresponding entry in the linkend=»catalog-pg- attrdef»>pg_attrde f catalog that actually defines the expression. (Check attgenerated to determine whether this is a default or a generation expression.)
atthasmissing bool This column has a value which is used where the column is entirely missing from the row, as happens when a column is added with a non-volatile DEFAULT value after the row is created. The actual value used is stored in the attmissingval column.
attidentity char If a zero byte („“), then not an identity column. Otherwise, a = generated always, d = generated by default.
attgenerated char If a zero byte („“), then not a generated column. Otherwise, s = stored. (Other values might be added in the future.)
attisdropped bool This column has been dropped and is no longer valid. A dropped column is still physically present in the table, but is ignored by the parser and so cannot be accessed via SQL.
attislocal bool This column is defined locally in the relation. Note that a column can be locally defined and inherited simultaneously.
attinhcount int4 The number of direct ancestors this column has. A column with a nonzero number of ancestors cannot be dropped nor renamed.
attcollation oid (references linkend=»catalog-pg- collation»>pg_coll ation.oid) The defined collation of the column, or zero if the column is not of a collatable data type
attacl aclitem[] Column-level access privileges, if any have been granted specifically on this column
attoptions text[] Attribute-level options, as keyword=value strings
attfdwoptions text[] Attribute-level foreign data wrapper options, as keyword=value strings
attmissingval anyarray This column has a one element array containing the value used when the column is entirely missing from the row, as happens when the column is added with a non-volatile DEFAULT value after the row is created. The value is only used when atthasmissing is true. If there is no value the column is null.

In a dropped column’s pg_attribute entry, atttypid is reset to zero, but attlen and the other fields copied from

linkend=»catalog-pg-type»>**pg_type** are still valid. This arrangement is needed

to cope with the situation where the dropped column’s data type was later dropped, and so there is no pg_type row anymore. attlen and the other fields can be used to interpret the contents of a row of the table.

9.2.8. pg_authid

The catalog pg_authid contains information about database authorization identifiers (roles). A role subsumes the concepts of users and groups. A user is essentially just a role with the rolcanlogin flag set. Any role (with or without rolcanlogin) can have other roles as members; see

linkend=»catalog-pg-auth-members»>**pg_auth_members**.

Since this catalog contains passwords, it must not be publicly readable.: linkend=»view-pg-roles»>**pg_roles**

is a publicly readable view on pg_authid that blanks out the password field.

user-manag contains detailed information about user and privilege management.

Because user identities are cluster-wide, pg_authid is shared across all databases of a cluster: there is only one copy of pg_authid per cluster, not one per database.

pg_authid Columns

Column Type Description
oid oid Row identifier
rolname name Role name
rolsuper bool Role has superuser privileges
rolinherit bool Role automatically inherits privileges of roles it is a member of
rolcreaterole bool Role can create more roles
rolcreatedb bool Role can create databases
rolcanlogin bool Role can log in. That is, this role can be given as the initial session authorization identifier.
rolreplication bool Role is a replication role. A replication role can initiate replication connections and create and drop replication slots.
rolbypassrls bool Role bypasses every row-level security policy, see ddl-rowsecurity for more information.
rolconnlimit int4 For roles that can log in, this sets maximum number of concurrent connections this role can make. -1 means no limit.
rolpassword text Password (possibly encrypted); null if none. The format depends on the form of encryption used.
rolvaliduntil timestamptz Password expiry time (only used for password authentication); null if no expiration

For an MD5 encrypted password, rolpassword column will begin with the string md5 followed by a 32-character hexadecimal MD5 hash. The MD5 hash will be of the user’s password concatenated to their user name. For example, if user joe has password xyzzy, PostgreSQL will store the md5 hash of xyzzyjoe.

If the password is encrypted with SCRAM-SHA-256, it has the format:

SCRAM-SHA-256$&lt;iteration count&gt;:&lt;salt&gt;$&lt;StoredKey&gt;:&lt;ServerKey&gt;

 where salt, StoredKey and

ServerKey are in Base64 encoded format. This format is the same as that specified by RFC 5803.

A password that does not follow either of those formats is assumed to be unencrypted.

9.2.9. pg_auth_members

The catalog pg_auth_members shows the membership relations between roles. Any non-circular set of relationships is allowed.

Because user identities are cluster-wide, pg_auth_members is shared across all databases of a cluster: there is only one copy of pg_auth_members per cluster, not one per database.

pg_auth_members Columns

Column Type Description
roleid oid (references linkend=»catalog-pg- authid»>*pg_authid .*oid) ID of a role that has a member
member oid (references linkend=»catalog-pg- authid»>*pg_authid .*oid) ID of a role that is a member of roleid
grantor oid (references linkend=»catalog-pg- authid»>*pg_authid .*oid) ID of the role that granted this membership
admin_option bool True if member can grant membership in roleid to others

9.2.10. pg_cast

The catalog pg_cast stores data type conversion paths, both built-in and user-defined.

It should be noted that pg_cast does not represent every type conversion that the system knows how to perform; only those that cannot be deduced from some generic rule. For example, casting between a domain and its base type is not explicitly represented in pg_cast. Another important exception is that automatic I/O conversion casts, those performed using a data type’s own I/O functions to convert to or from text or other string types, are not explicitly represented in pg_cast.

pg_cast Columns

Column Type Description
oid oid Row identifier
castsource oid (references linkend=»catalog-pg- type»>pg_type. oid) OID of the source data type
casttarget oid (references linkend=»catalog-pg- type»>pg_type. oid) OID of the target data type
castfunc oid (references linkend=»catalog-pg- proc»>pg_proc. oid) The OID of the function to use to perform this cast. Zero is stored if the cast method doesn’t require a function.
castcontext char Indicates what contexts the cast can be invoked in. e means only as an explicit cast (using CAST or :: syntax). a means implicitly in assignment to a target column, as well as explicitly. i means implicitly in expressions, as well as the other cases.
castmethod char Indicates how the cast is performed. f means that the function specified in the castfunc field is used. i means that the input/output functions are used. b means that the types are binary-coercible, thus no conversion is required.

The cast functions listed in pg_cast must always take the cast source type as their first argument type, and return the cast destination type as their result type. A cast function can have up to three arguments. The second argument, if present, must be type integer; it receives the type modifier associated with the destination type, or -1 if there is none. The third argument, if present, must be type boolean; it receives true if the cast is an explicit cast, false otherwise.

It is legitimate to create a pg_cast entry in which the source and target types are the same, if the associated function takes more than one argument. Such entries represent length coercion functions that coerce values of the type to be legal for a particular type modifier value.

When a pg_cast entry has different source and target types and a function that takes more than one argument, it represents converting from one type to another and applying a length coercion in a single step. When no such entry is available, coercion to a type that uses a type modifier involves two steps, one to convert between data types and a second to apply the modifier.

9.2.11. pg_class

The catalog pg_class catalogs tables and most everything else that has columns or is otherwise similar to a table. This includes indexes (but see also linkend=»catalog-pg-index»>**pg_index**), sequences (but see also linkend=»catalog-pg-sequence»>**pg_sequence**), views, materialized views, composite types, and TOAST tables; see relkind. Below, when we mean all of these kinds of objects we speak of relations. Not all columns are meaningful for all relation types.

pg_class Columns

Column Type Description
oid oid Row identifier
relname name Name of the table, index, view, etc.
relnamespace oid (references linkend=»catalog-pg- namespace»>pg_name space.oid) The OID of the namespace that contains this relation
reltype oid (references linkend=»catalog-pg- type»>pg_type. oid) The OID of the data type that corresponds to this table’s row type, if any; zero for indexes, sequences, and toast tables, which have no pg_type entry
reloftype oid (references linkend=»catalog-pg- type»>pg_type. oid) For typed tables, the OID of the underlying composite type; zero for all other relations
relowner oid (references linkend=»catalog-pg- authid»>*pg_authid .*oid) Owner of the relation
relam oid (references linkend=»catalog-pg- am»>pg_am.*oid *) If this is a table or an index, the access method used (heap, B-tree, hash, etc.); otherwise zero (zero occurs for sequences, as well as relations without storage, such as views)
relfilenode oid Name of the on-disk file of this relation; zero means this is a mapped relation whose disk file name is determined by low-level state
reltablespace oid (references linkend=»catalog-pg- tablespace»>pg_tab lespace.oid) The tablespace in which this relation is stored. If zero, the database’s default tablespace is implied. (Not meaningful if the relation has no on-disk file.)
relpages int4 Size of the on-disk representation of this table in pages (of size BLCKSZ). This is only an estimate used by the planner. It is updated by linkend=»sql-vacuum» >VACUUM, linkend=»sql-analyze «>ANALYZE, and a few DDL commands such as linkend=»sql-createi ndex»>CREATE INDEX.
reltuples float4 Number of live rows in the table. This is only an estimate used by the planner. It is updated by linkend=»sql-vacuum» >VACUUM, linkend=»sql-analyze «>ANALYZE, and a few DDL commands such as linkend=»sql-createi ndex»>CREATE INDEX. If the table has never yet been vacuumed or analyzed, reltuples contains -1 indicating that the row count is unknown.
relallvisible int4 Number of pages that are marked all-visible in the table’s visibility map. This is only an estimate used by the planner. It is updated by linkend=»sql-vacuum» >VACUUM, linkend=»sql-analyze «>ANALYZE, and a few DDL commands such as linkend=»sql-createi ndex»>CREATE INDEX.
reltoastrelid oid (references linkend=»catalog-pg- class»>pg_class. oid) OID of the TOAST table associated with this table, zero if none. The TOAST table stores large attributes out of line in a secondary table.
relhasindex bool True if this is a table and it has (or recently had) any indexes
relisshared bool True if this table is shared across all databases in the cluster. Only certain system catalogs (such as linkend=»catalog-pg- database»>pg_datab ase) are shared.
relpersistence char p = permanent table/sequence, u = unlogged table/sequence, t = temporary table/sequence
relkind char r = ordinary table, i = index, S = sequence, t = TOAST table, v = view, m = materialized view, c = composite type, f = foreign table, p = partitioned table, I = partitioned index
relnatts int2 Number of user columns in the relation (system columns not counted). There must be this many corresponding entries in linkend=»catalog-pg- attribute»>pg_attr ibute. See also pg_attribute.a ttnum.
relchecks int2 Number of CHECK constraints on the table; see linkend=»catalog-pg- constraint»>pg_con straint catalog
relhasrules bool True if table has (or once had) rules; see linkend=»catalog-pg- rewrite»>pg_rewrit e catalog
relhastriggers bool True if table has (or once had) triggers; see linkend=»catalog-pg- trigger»>pg_trigge r catalog
relhassubclass bool True if table or index has (or once had) any inheritance children or partitions
relrowsecurity bool True if table has row-level security enabled; see linkend=»catalog-pg- policy»>*pg_policy * catalog
relforcerowsecurit y bool True if row-level security (when enabled) will also apply to table owner; see linkend=»catalog-pg- policy»>*pg_policy * catalog
relispopulated bool True if relation is populated (this is true for all relations other than some materialized views)
relreplident char Columns used to form replica identity for rows: d = default (primary key, if any), n = nothing, f = all columns, i = index with indisreplident set (same as nothing if the index used has been dropped)
relispartition bool True if table or index is a partition
relrewrite oid (references linkend=»catalog-pg- class»>pg_class. oid) For new relations being written during a DDL operation that requires a table rewrite, this contains the OID of the original relation; otherwise zero. That state is only visible internally; this field should never contain anything other than zero for a user-visible relation.
relfrozenxid xid All transaction IDs before this one have been replaced with a permanent (frozen) transaction ID in this table. This is used to track whether the table needs to be vacuumed in order to prevent transaction ID wraparound or to allow pg_xact to be shrunk. Zero (InvalidTransactionI d) if the relation is not a table.
relminmxid xid All multixact IDs before this one have been replaced by a transaction ID in this table. This is used to track whether the table needs to be vacuumed in order to prevent multixact ID wraparound or to allow pg_multixact to be shrunk. Zero (InvalidMultiXactId) if the relation is not a table.
relacl aclitem[] Access privileges; see ddl-priv for details
reloptions text[] Access-method-specif ic options, as keyword=value strings
relpartbound pg_node_tree If table is a partition (see relispartition), internal representation of the partition bound

Several of the Boolean flags in pg_class are maintained lazily: they are guaranteed to be true if that’s the correct state, but may not be reset to false immediately when the condition is no longer true. For example, relhasindex is set by

linkend=»sql-createindex»>**CREATE INDEX**, but it is never cleared by linkend=»sql-dropindex»>**DROP INDEX**. Instead, linkend=»sql-vacuum»>**VACUUM** clears

relhasindex if it finds the table has no indexes. This arrangement avoids race conditions and improves concurrency.

9.2.12. pg_collation

The catalog pg_collation describes the available collations, which are essentially mappings from an SQL name to operating system locale categories. See collation for more information.

pg_collation Columns

Column Type Description
oid oid Row identifier
collname name Collation name (unique per namespace and encoding)
collnamespace oid (references linkend=»catalog-pg- namespace»>pg_name space.oid) The OID of the namespace that contains this collation
collowner oid (references linkend=»catalog-pg- authid»>*pg_authid .*oid) Owner of the collation
collprovider char Provider of the collation: d = database default, c = libc, i = icu
collisdeterministi c bool Is the collation deterministic?
collencoding int4 Encoding in which the collation is applicable, or -1 if it works for any encoding
collcollate text LC_COLLATE for this collation object
collctype text LC_CTYPE for this collation object
colliculocale text ICU locale ID for this collation object
collversion text Provider-specific version of the collation. This is recorded when the collation is created and then checked when it is used, to detect changes in the collation definition that could lead to data corruption.

Note that the unique key on this catalog is (collname, collencoding, collnamespace) not just (collname, collnamespace). PostgreSQL generally ignores all collations that do not have collencoding equal to either the current database’s encoding or -1, and creation of new entries with the same name as an entry with collencoding = -1 is forbidden. Therefore it is sufficient to use a qualified SQL name (schema.name) to identify a collation, even though this is not unique according to the catalog definition. The reason for defining the catalog this way is that initdb fills it in at cluster initialization time with entries for all locales available on the system, so it must be able to hold entries for all encodings that might ever be used in the cluster.

In the template0 database, it could be useful to create collations whose encoding does not match the database encoding, since they could match the encodings of databases later cloned from template0. This would currently have to be done manually.

9.2.13. pg_constraint

The catalog pg_constraint stores check, primary key, unique, foreign key, and exclusion constraints on tables. (Column constraints are not treated specially. Every column constraint is equivalent to some table constraint.) Not-null constraints are represented in the

linkend=»catalog-pg-attribute»>**pg_attribute**

catalog, not here.

User-defined constraint triggers (created with linkend=»sql-createtrigger»> CREATE CONSTRAINT TRIGGER) also give rise to an entry in this table.

Check constraints on domains are stored here, too.

pg_constraint Columns

Column Type Description
oid oid Row identifier
conname name Constraint name (not necessarily unique! )
connamespace oid (references linkend=»catalog-pg- namespace»>pg_name space.oid) The OID of the namespace that contains this constraint
contype char c = check constraint, f = foreign key constraint, p = primary key constraint, u = unique constraint, t = constraint trigger, x = exclusion constraint
condeferrable bool Is the constraint deferrable?
condeferred bool Is the constraint deferred by default?
convalidated bool Has the constraint been validated? Currently, can be false only for foreign keys and CHECK constraints
conrelid oid (references linkend=»catalog-pg- class»>pg_class. oid) The table this constraint is on; zero if not a table constraint
contypid oid (references linkend=»catalog-pg- type»>pg_type. oid) The domain this constraint is on; zero if not a domain constraint
conindid oid (references linkend=»catalog-pg- class»>pg_class. oid) The index supporting this constraint, if it’s a unique, primary key, foreign key, or exclusion constraint; else zero
conparentid oid (references linkend=»catalog-pg- constraint»>pg_con straint.oid) The corresponding constraint of the parent partitioned table, if this is a constraint on a partition; else zero
confrelid oid (references linkend=»catalog-pg- class»>pg_class. oid) If a foreign key, the referenced table; else zero
confupdtype char Foreign key update action code: a = no action, r = restrict, c = cascade, n = set null, d = set default
confdeltype char Foreign key deletion action code: a = no action, r = restrict, c = cascade, n = set null, d = set default
confmatchtype char Foreign key match type: f = full, p = partial, s = simple
conislocal bool This constraint is defined locally for the relation. Note that a constraint can be locally defined and inherited simultaneously.
coninhcount int4 The number of direct inheritance ancestors this constraint has. A constraint with a nonzero number of ancestors cannot be dropped nor renamed.
connoinherit bool This constraint is defined locally for the relation. It is a non-inheritable constraint.
conkey int2[] (references linkend=»catalog-pg- attribute»>pg_attr ibute.attnum) If a table constraint (including foreign keys, but not constraint triggers), list of the constrained columns
confkey int2[] (references linkend=»catalog-pg- attribute»>pg_attr ibute.attnum) If a foreign key, list of the referenced columns
conpfeqop oid[] (references linkend=»catalog-pg- operator»>pg_opera tor.oid) If a foreign key, list of the equality operators for PK = FK comparisons
conppeqop oid[] (references linkend=»catalog-pg- operator»>pg_opera tor.oid) If a foreign key, list of the equality operators for PK = PK comparisons
conffeqop oid[] (references linkend=»catalog-pg- operator»>pg_opera tor.oid) If a foreign key, list of the equality operators for FK = FK comparisons
confdelsetcols int2[] (references linkend=»catalog-pg- attribute»>pg_attr ibute.attnum) If a foreign key with a SET NULL or SET DEFAULT delete action, the columns that will be updated. If null, all of the referencing columns will be updated.
conexclop oid[] (references linkend=»catalog-pg- operator»>pg_opera tor.oid) If an exclusion constraint, list of the per-column exclusion operators
conbin pg_node_tree If a check constraint, an internal representation of the expression. (It’s recommended to use pg_get_constraintd ef() to extract the definition of a check constraint.)

In the case of an exclusion constraint, conkey is only useful for constraint elements that are simple column references. For other cases, a zero appears in conkey and the associated index must be consulted to discover the expression that is constrained. (conkey thus has the same contents as linkend=»catalog-pg-index»>**pg_index**.**indkey** for the index.)

Примечание

pg_class.relchecks needs to agree with the number of check-constraint entries found in this table for each relation.

9.2.14. pg_conversion

The catalog pg_conversion describes encoding conversion functions. See sql-createconversion for more information.

pg_conversion Columns

Column Type Description
oid oid Row identifier
conname name Conversion name (unique within a namespace)
connamespace oid (references linkend=»catalog-pg- namespace»>pg_name space.oid) The OID of the namespace that contains this conversion
conowner oid (references linkend=»catalog-pg- authid»>*pg_authid .*oid) Owner of the conversion
conforencoding int4 Source encoding ID ( linkend=»pg-encoding -to-char»>pg_encod ing_to_char() can translate this number to the encoding name)
contoencoding int4 Destination encoding ID ( linkend=»pg-encoding -to-char»>pg_encod ing_to_char() can translate this number to the encoding name)
conproc regproc (references linkend=»catalog-pg- proc»>pg_proc. oid) Conversion function
condefault bool True if this is the default conversion

9.2.15. pg_database

The catalog pg_database stores information about the available databases. Databases are created with the linkend=»sql-createdatabase»>**CREATE DATABASE** command. Consult managing-databases for details about the meaning of some of the parameters.

Unlike most system catalogs, pg_database is shared across all databases of a cluster: there is only one copy of pg_database per cluster, not one per database.

pg_database Columns

Column Type Description
oid oid Row identifier
datname name Database name
datdba oid (references linkend=»catalog-pg- authid»>*pg_authid .*oid) Owner of the database, usually the user who created it
encoding int4 Character encoding for this database ( linkend=»pg-encoding -to-char»>pg_encod ing_to_char() can translate this number to the encoding name)
datlocprovider char Locale provider for this database: c = libc, i = icu
datistemplate bool If true, then this database can be cloned by any user with CREATEDB privileges; if false, then only superusers or the owner of the database can clone it.
datallowconn bool If false then no one can connect to this database. This is used to protect the template0 database from being altered.
datconnlimit int4 Sets maximum number of concurrent connections that can be made to this database. -1 means no limit.
datfrozenxid xid All transaction IDs before this one have been replaced with a permanent (frozen) transaction ID in this database. This is used to track whether the database needs to be vacuumed in order to prevent transaction ID wraparound or to allow pg_xact to be shrunk. It is the minimum of the per-table linkend=»catalog-pg- class»>pg_class. relfrozenxid values.
datminmxid xid All multixact IDs before this one have been replaced with a transaction ID in this database. This is used to track whether the database needs to be vacuumed in order to prevent multixact ID wraparound or to allow pg_multixact to be shrunk. It is the minimum of the per-table linkend=»catalog-pg- class»>pg_class. relminmxid values.
dattablespace oid (references linkend=»catalog-pg- tablespace»>pg_tab lespace.oid) The default tablespace for the database. Within this database, all tables for which linkend=»catalog-pg- class»>pg_class. reltablespace is zero will be stored in this tablespace; in particular, all the non-shared system catalogs will be there.
datcollate text LC_COLLATE for this database
datctype text LC_CTYPE for this database
daticulocale text ICU locale ID for this database
datcollversion text Provider-specific version of the collation. This is recorded when the database is created and then checked when it is used, to detect changes in the collation definition that could lead to data corruption.
datacl aclitem[] Access privileges; see ddl-priv for details

9.2.16. pg_db_role_setting

The catalog pg_db_role_setting records the default values that have been set for run-time configuration variables, for each role and database combination.

Unlike most system catalogs, pg_db_role_setting is shared across all databases of a cluster: there is only one copy of pg_db_role_setting per cluster, not one per database.

pg_db_role_setting Columns

Column Type Description
setdatabase oid (references linkend=»catalog-pg- database»>pg_datab ase.oid) The OID of the database the setting is applicable to, or zero if not database-specific
setrole oid (references linkend=»catalog-pg- authid»>*pg_authid .*oid) The OID of the role the setting is applicable to, or zero if not role-specific
setconfig text[] Defaults for run-time configuration variables

9.2.17. pg_default_acl

The catalog pg_default_acl stores initial privileges to be assigned to newly created objects.

pg_default_acl Columns

Column Type Description
oid oid Row identifier
defaclrole oid (references linkend=»catalog-pg- authid»>*pg_authid .*oid) The OID of the role associated with this entry
defaclnamespace oid (references linkend=»catalog-pg- namespace»>pg_name space.oid) The OID of the namespace associated with this entry, or zero if none
defaclobjtype char Type of object this entry is for: r = relation (table, view), S = sequence, f = function, T = type, n = schema
defaclacl aclitem[] Access privileges that this type of object should have on creation

A pg_default_acl entry shows the initial privileges to be assigned to an object belonging to the indicated user. There are currently two types of entry: global entries with defaclnamespace = zero, and per-schema entries that reference a particular schema. If a global entry is present then it overrides the normal hard-wired default privileges for the object type. A per-schema entry, if present, represents privileges to be added to the global or hard-wired default privileges.

Note that when an ACL entry in another catalog is null, it is taken to represent the hard-wired default privileges for its object, not whatever might be in pg_default_acl at the moment. pg_default_acl is only consulted during object creation.

9.2.18. pg_depend

The catalog pg_depend records the dependency relationships between database objects. This information allows DROP commands to find which other objects must be dropped by DROP CASCADE or prevent dropping in the DROP RESTRICT case.

See also linkend=»catalog-pg-shdepend»>**pg_shdepend**, which performs a similar function for dependencies involving objects that are shared across a database cluster.

pg_depend Columns

Column Type Description
classid oid (references linkend=»catalog-pg- class»>pg_class. oid) The OID of the system catalog the dependent object is in
objid oid (references any OID column) The OID of the specific dependent object
objsubid int4 For a table column, this is the column number (the objid and classid refer to the table itself). For all other object types, this column is zero.
refclassid oid (references linkend=»catalog-pg- class»>pg_class. oid) The OID of the system catalog the referenced object is in
refobjid oid (references any OID column) The OID of the specific referenced object
refobjsubid int4 For a table column, this is the column number (the refobjid and refclassid refer to the table itself). For all other object types, this column is zero.
deptype char A code defining the specific semantics of this dependency relationship; see text

In all cases, a pg_depend entry indicates that the referenced object cannot be dropped without also dropping the dependent object. However, there are several subflavors identified by deptype:

Other dependency flavors might be needed in future.

Note that it’s quite possible for two objects to be linked by more than one pg_depend entry. For example, a child partitioned index would have both a partition-type dependency on its associated partition table, and an auto dependency on each column of that table that it indexes. This sort of situation expresses the union of multiple dependency semantics. A dependent object can be dropped without CASCADE if any of its dependencies satisfies its condition for automatic dropping. Conversely, all the dependencies“ restrictions about which objects must be dropped together must be satisfied.

Most objects created during initdb are considered pinned, which means that the system itself depends on them. Therefore, they are never allowed to be dropped. Also, knowing that pinned objects will not be dropped, the dependency mechanism doesn’t bother to make pg_depend entries showing dependencies on them. Thus, for example, a table column of type numeric notionally has a NORMAL dependency on the numeric data type, but no such entry actually appears in pg_depend.

9.2.19. pg_description

The catalog pg_description stores optional descriptions (comments) for each database object. Descriptions can be manipulated with the linkend=»sql-comment»>**COMMENT** command and viewed with psql’s d commands. Descriptions of many built-in system objects are provided in the initial contents of pg_description.

See also linkend=»catalog-pg-shdescription»>**pg_shdescription**, which performs a similar function for descriptions involving objects that are shared across a database cluster.

pg_description Columns

Column Type Description
objoid oid (references any OID column) The OID of the object this description pertains to
classoid oid (references linkend=»catalog-pg- class»>pg_class. oid) The OID of the system catalog this object appears in
objsubid int4 For a comment on a table column, this is the column number (the objoid and classoid refer to the table itself). For all other object types, this column is zero.
description text Arbitrary text that serves as the description of this object

9.2.20. pg_enum

The pg_enum catalog contains entries showing the values and labels for each enum type. The internal representation of a given enum value is actually the OID of its associated row in pg_enum.

pg_enum Columns

Column Type Description
oid oid Row identifier
enumtypid oid (references linkend=»catalog-pg- type»>pg_type. oid) The OID of the linkend=»catalog-pg- type»>pg_type entry owning this enum value
enumsortorder float4 The sort position of this enum value within its enum type
enumlabel name The textual label for this enum value

The OIDs for pg_enum rows follow a special rule: even-numbered OIDs are guaranteed to be ordered in the same way as the sort ordering of their enum type. That is, if two even OIDs belong to the same enum type, the smaller OID must have the smaller enumsortorder value. Odd-numbered OID values need bear no relationship to the sort order. This rule allows the enum comparison routines to avoid catalog lookups in many common cases. The routines that create and alter enum types attempt to assign even OIDs to enum values whenever possible.

When an enum type is created, its members are assigned sort-order positions 1..n. But members added later might be given negative or fractional values of enumsortorder. The only requirement on these values is that they be correctly ordered and unique within each enum type.

9.2.21. pg_event_trigger

The catalog pg_event_trigger stores event triggers. See event-triggers for more information.

pg_event_trigger Columns

Column Type Description
oid oid Row identifier
evtname name Trigger name (must be unique)
evtevent name Identifies the event for which this trigger fires
evtowner oid (references linkend=»catalog-pg- authid»>*pg_authid .*oid) Owner of the event trigger
evtfoid oid (references linkend=»catalog-pg- proc»>pg_proc. oid) The function to be called
evtenabled char Controls in which guc-session-replicat ion-role modes the event trigger fires. O = trigger fires in origin and local modes, D = trigger is disabled, R = trigger fires in replica mode, A = trigger fires always.
evttags text[] Command tags for which this trigger will fire. If NULL, the firing of this trigger is not restricted on the basis of the command tag.

9.2.22. pg_extension

The catalog pg_extension stores information about the installed extensions. See extend-extensions for details about extensions.

pg_extension Columns

Column Type Description
oid oid Row identifier
extname name Name of the extension
extowner oid (references linkend=»catalog-pg- authid»>*pg_authid .*oid) Owner of the extension
extnamespace oid (references linkend=»catalog-pg- namespace»>pg_name space.oid) Schema containing the extension’s exported objects
extrelocatable bool True if extension can be relocated to another schema
extversion text Version name for the extension
extconfig oid[] (references linkend=»catalog-pg- class»>pg_class. oid) Array of regclass OIDs for the extension’s configuration table(s), or NULL if none
extcondition text[] Array of WHERE-clause filter conditions for the extension’s configuration table(s), or NULL if none

Note that unlike most catalogs with a namespace column, extnamespace is not meant to imply that the extension belongs to that schema. Extension names are never schema-qualified. Rather, extnamespace indicates the schema that contains most or all of the extension’s objects. If extrelocatable is true, then this schema must in fact contain all schema-qualifiable objects belonging to the extension.

9.2.23. pg_foreign_data_wrapper

The catalog pg_foreign_data_wrapper stores foreign-data wrapper definitions. A foreign-data wrapper is the mechanism by which external data, residing on foreign servers, is accessed.

pg_foreign_data_wrapper Columns

Column Type Description
oid oid Row identifier
fdwname name Name of the foreign-data wrapper
fdwowner oid (references linkend=»catalog-pg- authid»>*pg_authid .*oid) Owner of the foreign-data wrapper
fdwhandler oid (references linkend=»catalog-pg- proc»>pg_proc. oid) References a handler function that is responsible for supplying execution routines for the foreign-data wrapper. Zero if no handler is provided
fdwvalidator oid (references linkend=»catalog-pg- proc»>pg_proc. oid) References a validator function that is responsible for checking the validity of the options given to the foreign-data wrapper, as well as options for foreign servers and user mappings using the foreign-data wrapper. Zero if no validator is provided
fdwacl aclitem[] Access privileges; see ddl-priv for details
fdwoptions text[] Foreign-data wrapper specific options, as keyword=value strings

9.2.24. pg_foreign_server

The catalog pg_foreign_server stores foreign server definitions. A foreign server describes a source of external data, such as a remote server. Foreign servers are accessed via foreign-data wrappers.

pg_foreign_server Columns

Column Type Description
oid oid Row identifier
srvname name Name of the foreign server
srvowner oid (references linkend=»catalog-pg- authid»>*pg_authid .*oid) Owner of the foreign server
srvfdw oid (references linkend=»catalog-pg- foreign-data-wrapper «>pg_foreign_data_ wrapper.oid) OID of the foreign-data wrapper of this foreign server
srvtype text Type of the server (optional)
srvversion text Version of the server (optional)
srvacl aclitem[] Access privileges; see ddl-priv for details
srvoptions text[] Foreign server specific options, as keyword=value strings

9.2.25. pg_foreign_table

The catalog pg_foreign_table contains auxiliary information about foreign tables. A foreign table is primarily represented by a

linkend=»catalog-pg-class»>**pg_class**

entry, just like a regular table. Its pg_foreign_table entry contains the information that is pertinent only to foreign tables and not any other kind of relation.

pg_foreign_table Columns

Column Type Description
ftrelid oid (references linkend=»catalog-pg- class»>pg_class. oid) The OID of the linkend=»catalog-pg- class»>pg_class entry for this foreign table
ftserver oid (references linkend=»catalog-pg- foreign-server»>pg _foreign_server. oid) OID of the foreign server for this foreign table
ftoptions text[] Foreign table options, as keyword=value strings

9.2.26. pg_index

The catalog pg_index contains part of the information about indexes. The rest is mostly in

linkend=»catalog-pg-class»>**pg_class**.

pg_index Columns

Column Type Description
indexrelid oid (references linkend=»catalog-pg- class»>pg_class. oid) The OID of the linkend=»catalog-pg- class»>pg_class entry for this index
indrelid oid (references linkend=»catalog-pg- class»>pg_class. oid) The OID of the linkend=»catalog-pg- class»>pg_class entry for the table this index is for
indnatts int2 The total number of columns in the index (duplicates *pg_class.relnatts *); this number includes both key and included attributes
indnkeyatts int2 The number of key columns in the index, not counting any included columns, which are merely stored and do not participate in the index semantics
indisunique bool If true, this is a unique index
indnullsnotdistinc t bool This value is only used for unique indexes. If false, this unique index will consider null values distinct (so the index can contain multiple null values in a column, the default PostgreSQL behavior). If it is true, it will consider null values to be equal (so the index can only contain one null value in a column).
indisprimary bool If true, this index represents the primary key of the table (indisunique should always be true when this is true)
indisexclusion bool If true, this index supports an exclusion constraint
indimmediate bool If true, the uniqueness check is enforced immediately on insertion (irrelevant if indisunique is not true)
indisclustered bool If true, the table was last clustered on this index
indisvalid bool If true, the index is currently valid for queries. False means the index is possibly incomplete: it must still be modified by linkend=»sql-insert» >INSERT/ linkend=»sql-update» >UPDATE operations, but it cannot safely be used for queries. If it is unique, the uniqueness property is not guaranteed true either.
indcheckxmin bool If true, queries must not use the index until the xmin of this pg_index row is below their TransactionXmin event horizon, because the table may contain broken linkend=»storage-hot «>HOT chains with incompatible rows that they can see
indisready bool If true, the index is currently ready for inserts. False means the index must be ignored by linkend=»sql-insert» >INSERT/ linkend=»sql-update» >UPDATE operations.
indislive bool If false, the index is in process of being dropped, and should be ignored for all purposes (including HOT-safety decisions)
indisreplident bool If true this index has been chosen as replica identity using linkend=»sql-alterta ble-replica-identity «>ALTER TABLE … REPLICA IDENTITY USING INDEX …
indkey int2vector (references linkend=»catalog-pg- attribute»>pg_attr ibute.attnum) This is an array of indnatts values that indicate which table columns this index indexes. For example, a value of 1 3 would mean that the first and the third table columns make up the index entries. Key columns come before non-key (included) columns. A zero in this array indicates that the corresponding index attribute is an expression over the table columns, rather than a simple column reference.
indcollation oidvector (references linkend=»catalog-pg- collation»>pg_coll ation.oid) For each column in the index key (indnkeyatts values), this contains the OID of the collation to use for the index, or zero if the column is not of a collatable data type.
indclass oidvector (references linkend=»catalog-pg- opclass»>pg_opclas s.oid) For each column in the index key (indnkeyatts values), this contains the OID of the operator class to use. See linkend=»catalog-pg- opclass»>pg_opclas s for details.
indoption int2vector This is an array of indnkeyatts values that store per-column flag bits. The meaning of the bits is defined by the index’s access method.
indexprs pg_node_tree Expression trees (in nodeToString() representation) for index attributes that are not simple column references. This is a list with one element for each zero entry in indkey. Null if all index attributes are simple references.
indpred pg_node_tree Expression tree (in nodeToString() representation) for partial index predicate. Null if not a partial index.

9.2.27. pg_inherits

The catalog pg_inherits records information about table and index inheritance hierarchies. There is one entry for each direct parent-child table or index relationship in the database. (Indirect inheritance can be determined by following chains of entries.)

pg_inherits Columns

Column Type Description
inhrelid oid (references linkend=»catalog-pg- class»>pg_class. oid) The OID of the child table or index
inhparent oid (references linkend=»catalog-pg- class»>pg_class. oid) The OID of the parent table or index
inhseqno int4 If there is more than one direct parent for a child table (multiple inheritance), this number tells the order in which the inherited columns are to be arranged. The count starts at 1. Indexes cannot have multiple inheritance, since they can only inherit when using declarative partitioning.
inhdetachpending bool true for a partition that is in the process of being detached; false otherwise.

9.2.28. pg_init_privs

The catalog pg_init_privs records information about the initial privileges of objects in the system. There is one entry for each object in the database which has a non-default (non-NULL) initial set of privileges.

Objects can have initial privileges either by having those privileges set when the system is initialized (by initdb) or when the object is created during a linkend=»sql-createextension»>**CREATE EXTENSION** and the extension script sets initial privileges using the linkend=»sql-grant»>**GRANT** system. Note that the system will automatically handle recording of the privileges during the extension script and that extension authors need only use the GRANT and REVOKE statements in their script to have the privileges recorded. The privtype column indicates if the initial privilege was set by initdb or during a CREATE EXTENSION command.

Objects which have initial privileges set by initdb will have entries where privtype is „i“, while objects which have initial privileges set by CREATE EXTENSION will have entries where privtype is „e“.

pg_init_privs Columns

Column Type Description
objoid oid (references any OID column) The OID of the specific object
classoid oid (references linkend=»catalog-pg- class»>pg_class. oid) The OID of the system catalog the object is in
objsubid int4 For a table column, this is the column number (the objoid and classoid refer to the table itself). For all other object types, this column is zero.
privtype char A code defining the type of initial privilege of this object; see text
initprivs aclitem[] The initial access privileges; see ddl-priv for details

9.2.29. pg_language

The catalog pg_language registers languages in which you can write functions or stored procedures. See sql-createlanguage and xplang for more information about language handlers.

pg_language Columns

Column Type Description
oid oid Row identifier
lanname name Name of the language
lanowner oid (references linkend=»catalog-pg- authid»>*pg_authid .*oid) Owner of the language
lanispl bool This is false for internal languages (such as SQL) and true for user-defined languages. Currently, pg_dump still uses this to determine which languages need to be dumped, but this might be replaced by a different mechanism in the future.
lanpltrusted bool True if this is a trusted language, which means that it is believed not to grant access to anything outside the normal SQL execution environment. Only superusers can create functions in untrusted languages.
lanplcallfoid oid (references linkend=»catalog-pg- proc»>pg_proc. oid) For noninternal languages this references the language handler, which is a special function that is responsible for executing all functions that are written in the particular language. Zero for internal languages.
laninline oid (references linkend=»catalog-pg- proc»>pg_proc. oid) This references a function that is responsible for executing inline anonymous code blocks (sql-do blocks). Zero if inline blocks are not supported.
lanvalidator oid (references linkend=»catalog-pg- proc»>pg_proc. oid) This references a language validator function that is responsible for checking the syntax and validity of new functions when they are created. Zero if no validator is provided.
lanacl aclitem[] Access privileges; see ddl-priv for details

9.2.30. pg_largeobject

The catalog pg_largeobject holds the data making up large objects. A large object is identified by an OID assigned when it is created. Each large object is broken into segments or pages small enough to be conveniently stored as rows in pg_largeobject. The amount of data per page is defined to be LOBLKSIZE (which is currently BLCKSZ/4, or typically 2 kB).

Prior to PostgreSQL 9.0, there was no permission structure associated with large objects. As a result, pg_largeobject was publicly readable and could be used to obtain the OIDs (and contents) of all large objects in the system. This is no longer the case; use

linkend=»catalog-pg-largeobject-metadata»>**pg_largeobject_metadata**

to obtain a list of large object OIDs.

pg_largeobject Columns

Column Type Description
loid oid (references linkend=»catalog-pg- largeobject-metadata «>pg_largeobject_m etadata.oid) Identifier of the large object that includes this page
pageno int4 Page number of this page within its large object (counting from zero)
data bytea Actual data stored in the large object. This will never be more than LOBLKSIZE bytes and might be less.

Each row of pg_largeobject holds data for one page of a large object, beginning at byte offset (pageno * LOBLKSIZE) within the object. The implementation allows sparse storage: pages might be missing, and might be shorter than LOBLKSIZE bytes even if they are not the last page of the object. Missing regions within a large object read as zeroes.

9.2.31. pg_largeobject_metadata

The catalog pg_largeobject_metadata holds metadata associated with large objects. The actual large object data is stored in

linkend=»catalog-pg-largeobject»>**pg_largeobject**.

pg_largeobject_metadata Columns

Column Type Description
oid oid Row identifier
lomowner oid (references linkend=»catalog-pg- authid»>*pg_authid .*oid) Owner of the large object
lomacl aclitem[] Access privileges; see ddl-priv for details

9.2.32. pg_namespace

The catalog pg_namespace stores namespaces. A namespace is the structure underlying SQL schemas: each namespace can have a separate collection of relations, types, etc. without name conflicts.

pg_namespace Columns

Column Type Description
oid oid Row identifier
nspname name Name of the namespace
nspowner oid (references linkend=»catalog-pg- authid»>*pg_authid .*oid) Owner of the namespace
nspacl aclitem[] Access privileges; see ddl-priv for details

9.2.33. pg_opclass

The catalog pg_opclass defines index access method operator classes. Each operator class defines semantics for index columns of a particular data type and a particular index access method. An operator class essentially specifies that a particular operator family is applicable to a particular indexable column data type. The set of operators from the family that are actually usable with the indexed column are whichever ones accept the column’s data type as their left-hand input.

Operator classes are described at length in xindex.

pg_opclass Columns

Column Type Description
oid oid Row identifier
opcmethod oid (references linkend=»catalog-pg- am»>pg_am.*oid *) Index access method operator class is for
opcname name Name of this operator class
opcnamespace oid (references linkend=»catalog-pg- namespace»>pg_name space.oid) Namespace of this operator class
opcowner oid (references linkend=»catalog-pg- authid»>*pg_authid .*oid) Owner of the operator class
opcfamily oid (references linkend=»catalog-pg- opfamily»>pg_opfam ily.oid) Operator family containing the operator class
opcintype oid (references linkend=»catalog-pg- type»>pg_type. oid) Data type that the operator class indexes
opcdefault bool True if this operator class is the default for opcintype
opckeytype oid (references linkend=»catalog-pg- type»>pg_type. oid) Type of data stored in index, or zero if same as opcintype

An operator class’s opcmethod must match the opfmethod of its containing operator family. Also, there must be no more than one pg_opclass row having opcdefault true for any given combination of opcmethod and opcintype.

9.2.34. pg_operator

The catalog pg_operator stores information about operators. See sql-createoperator and xoper for more information.

pg_operator Columns

Column Type Description
oid oid Row identifier
oprname name Name of the operator
oprnamespace oid (references linkend=»catalog-pg- namespace»>pg_name space.oid) The OID of the namespace that contains this operator
oprowner oid (references linkend=»catalog-pg- authid»>*pg_authid .*oid) Owner of the operator
oprkind char b = infix operator (both), or l = prefix operator (left)
oprcanmerge bool This operator supports merge joins
oprcanhash bool This operator supports hash joins
oprleft oid (references linkend=»catalog-pg- type»>pg_type. oid) Type of the left operand (zero for a prefix operator)
oprright oid (references linkend=»catalog-pg- type»>pg_type. oid) Type of the right operand
oprresult oid (references linkend=»catalog-pg- type»>pg_type. oid) Type of the result (zero for a not-yet-defined shell operator)
oprcom oid (references linkend=»catalog-pg- operator»>pg_opera tor.oid) Commutator of this operator (zero if none)
oprnegate oid (references linkend=»catalog-pg- operator»>pg_opera tor.oid) Negator of this operator (zero if none)
oprcode regproc (references linkend=»catalog-pg- proc»>pg_proc. oid) Function that implements this operator (zero for a not-yet-defined shell operator)
oprrest regproc (references linkend=»catalog-pg- proc»>pg_proc. oid) Restriction selectivity estimation function for this operator (zero if none)
oprjoin regproc (references linkend=»catalog-pg- proc»>pg_proc. oid) Join selectivity estimation function for this operator (zero if none)

9.2.35. pg_opfamily

The catalog pg_opfamily defines operator families. Each operator family is a collection of operators and associated support routines that implement the semantics specified for a particular index access method. Furthermore, the operators in a family are all compatible, in a way that is specified by the access method. The operator family concept allows cross-data-type operators to be used with indexes and to be reasoned about using knowledge of access method semantics.

Operator families are described at length in xindex.

pg_opfamily Columns

Column Type Description
oid oid Row identifier
opfmethod oid (references linkend=»catalog-pg- am»>pg_am.*oid *) Index access method operator family is for
opfname name Name of this operator family
opfnamespace oid (references linkend=»catalog-pg- namespace»>pg_name space.oid) Namespace of this operator family
opfowner oid (references linkend=»catalog-pg- authid»>*pg_authid .*oid) Owner of the operator family

The majority of the information defining an operator family is not in its pg_opfamily row, but in the associated rows in

linkend=»catalog-pg-amop»>**pg_amop**, linkend=»catalog-pg-amproc»>**pg_amproc**,

and: linkend=»catalog-pg-opclass»>**pg_opclass**.

9.2.36. pg_parameter_acl

The catalog pg_parameter_acl records configuration parameters for which privileges have been granted to one or more roles. No entry is made for parameters that have default privileges.

Unlike most system catalogs, pg_parameter_acl is shared across all databases of a cluster: there is only one copy of pg_parameter_acl per cluster, not one per database.

pg_parameter_acl Columns

Column Type Description
oid oid Row identifier
parname text The name of a configuration parameter for which privileges are granted
paracl aclitem[] Access privileges; see ddl-priv for details

9.2.37. pg_partitioned_table

The catalog pg_partitioned_table stores information about how tables are partitioned.

pg_partitioned_table Columns

Column Type Description
partrelid oid (references linkend=»catalog-pg- class»>pg_class. oid) The OID of the linkend=»catalog-pg- class»>pg_class entry for this partitioned table
partstrat char Partitioning strategy; h = hash partitioned table, l = list partitioned table, r = range partitioned table
partnatts int2 The number of columns in the partition key
partdefid oid (references linkend=»catalog-pg- class»>pg_class. oid) The OID of the linkend=»catalog-pg- class»>pg_class entry for the default partition of this partitioned table, or zero if this partitioned table does not have a default partition
partattrs int2vector (references linkend=»catalog-pg- attribute»>pg_attr ibute.attnum) This is an array of partnatts values that indicate which table columns are part of the partition key. For example, a value of 1 3 would mean that the first and the third table columns make up the partition key. A zero in this array indicates that the corresponding partition key column is an expression, rather than a simple column reference.
partclass oidvector (references linkend=»catalog-pg- opclass»>pg_opclas s.oid) For each column in the partition key, this contains the OID of the operator class to use. See linkend=»catalog-pg- opclass»>pg_opclas s for details.
partcollation oidvector (references linkend=»catalog-pg- collation»>pg_coll ation.oid) For each column in the partition key, this contains the OID of the collation to use for partitioning, or zero if the column is not of a collatable data type.
partexprs pg_node_tree Expression trees (in nodeToString() representation) for partition key columns that are not simple column references. This is a list with one element for each zero entry in partattrs. Null if all partition key columns are simple references.

9.2.38. pg_policy

The catalog pg_policy stores row-level security policies for tables. A policy includes the kind of command that it applies to (possibly all commands), the roles that it applies to, the expression to be added as a security-barrier qualification to queries that include the table, and the expression to be added as a WITH CHECK option for queries that attempt to add new records to the table.

pg_policy Columns

Column Type Description
oid oid Row identifier
polname name The name of the policy
polrelid oid (references linkend=»catalog-pg- class»>pg_class. oid) The table to which the policy applies
polcmd char The command type to which the policy is applied: r for sql-select, a for sql-insert, w for sql-update, d for sql-delete, or * for all
polpermissive bool Is the policy permissive or restrictive?
polroles oid[] (references linkend=»catalog-pg- authid»>*pg_authid .*oid) The roles to which the policy is applied; zero means PUBLIC (and normally appears alone in the array)
polqual pg_node_tree The expression tree to be added to the security barrier qualifications for queries that use the table
polwithcheck pg_node_tree The expression tree to be added to the WITH CHECK qualifications for queries that attempt to add rows to the table

Примечание

Policies stored in pg_policy are applied only when: linkend=»catalog-pg-class»>**pg_class**.**relrowsecurity** is set for

their table.

9.2.39. pg_proc

The catalog pg_proc stores information about functions, procedures, aggregate functions, and window functions (collectively also known as routines). See sql-createfunction, sql-createprocedure, and xfunc for more information.

If prokind indicates that the entry is for an aggregate function, there should be a matching row in

linkend=»catalog-pg-aggregate»>**pg_aggregate**.

pg_proc Columns

Column Type Description
oid oid Row identifier
proname name Name of the function
pronamespace oid (references linkend=»catalog-pg- namespace»>pg_name space.oid) The OID of the namespace that contains this function
proowner oid (references linkend=»catalog-pg- authid»>*pg_authid .*oid) Owner of the function
prolang oid (references linkend=»catalog-pg- language»>pg_langu age.oid) Implementation language or call interface of this function
procost float4 Estimated execution cost (in units of guc-cpu-operator-cos t); if proretset, this is cost per row returned
prorows float4 Estimated number of result rows (zero if not proretset)
provariadic oid (references linkend=»catalog-pg- type»>pg_type. oid) Data type of the variadic array parameter’s elements, or zero if the function does not have a variadic parameter
prosupport regproc (references linkend=»catalog-pg- proc»>pg_proc. oid) Planner support function for this function (see xfunc-optimization), or zero if none
prokind char f for a normal function, p for a procedure, a for an aggregate function, or w for a window function
prosecdef bool Function is a security definer (i.e., a setuid function)
proleakproof bool The function has no side effects. No information about the arguments is conveyed except via the return value. Any function that might throw an error depending on the values of its arguments is not leak-proof.
proisstrict bool Function returns null if any call argument is null. In that case the function won’t actually be called at all. Functions that are not strict must be prepared to handle null inputs.
proretset bool Function returns a set (i.e., multiple values of the specified data type)
provolatile char provolatile tells whether the function’s result depends only on its input arguments, or is affected by outside factors. It is i for immutable functions, which always deliver the same result for the same inputs. It is s for stable functions, whose results (for fixed inputs) do not change within a scan. It is v for volatile functions, whose results might change at any time. (Use v also for functions with side-effects, so that calls to them cannot get optimized away.)
proparallel char proparallel tells whether the function can be safely run in parallel mode. It is s for functions which are safe to run in parallel mode without restriction. It is r for functions which can be run in parallel mode, but their execution is restricted to the parallel group leader; parallel worker processes cannot invoke these functions. It is u for functions which are unsafe in parallel mode; the presence of such a function forces a serial execution plan.
pronargs int2 Number of input arguments
pronargdefaults int2 Number of arguments that have defaults
prorettype oid (references linkend=»catalog-pg- type»>pg_type. oid) Data type of the return value
proargtypes oidvector (references linkend=»catalog-pg- type»>pg_type. oid) An array of the data types of the function arguments. This includes only input arguments (including INOUT and VARIADIC arguments), and thus represents the call signature of the function.
proallargtypes oid[] (references linkend=»catalog-pg- type»>pg_type. oid) An array of the data types of the function arguments. This includes all arguments (including OUT and INOUT arguments); however, if all the arguments are IN arguments, this field will be null. Note that subscripting is 1-based, whereas for historical reasons proargtypes is subscripted from 0.
proargmodes char[] An array of the modes of the function arguments, encoded as i for IN arguments, o for OUT arguments, b for INOUT arguments, v for VARIADIC arguments, t for TABLE arguments. If all the arguments are IN arguments, this field will be null. Note that subscripts correspond to positions of proallargtypes not proargtypes.
proargnames text[] An array of the names of the function arguments. Arguments without a name are set to empty strings in the array. If none of the arguments have a name, this field will be null. Note that subscripts correspond to positions of proallargtypes not proargtypes.
proargdefaults pg_node_tree Expression trees (in nodeToString() representation) for default values. This is a list with pronargdefaults elements, corresponding to the last N input arguments (i.e., the last N proargtypes positions). If none of the arguments have defaults, this field will be null.
protrftypes oid[] (references linkend=»catalog-pg- type»>pg_type. oid) An array of the argument/result data type(s) for which to apply transforms (from the function’s TRANSFORM clause). Null if none.
prosrc text This tells the function handler how to invoke the function. It might be the actual source code of the function for interpreted languages, a link symbol, a file name, or just about anything else, depending on the implementation language/call convention.
probin text Additional information about how to invoke the function. Again, the interpretation is language-specific.
prosqlbody pg_node_tree Pre-parsed SQL function body. This is used for SQL-language functions when the body is given in SQL-standard notation rather than as a string literal. It’s null in other cases.
proconfig text[] Function’s local settings for run-time configuration variables
proacl aclitem[] Access privileges; see ddl-priv for details

For compiled functions, both built-in and dynamically loaded, prosrc contains the function’s C-language name (link symbol). For SQL-language functions, prosrc contains the function’s source text if that is specified as a string literal; but if the function body is specified in SQL-standard style, prosrc is unused (typically it’s an empty string) and prosqlbody contains the pre-parsed definition. For all other currently-known language types, prosrc contains the function’s source text. probin is null except for dynamically-loaded C functions, for which it gives the name of the shared library file containing the function.

9.2.40. pg_publication

The catalog pg_publication contains all publications created in the database. For more on publications see logical-replication-publication.

pg_publication Columns

Column Type Description
oid oid Row identifier
pubname name Name of the publication
pubowner oid (references linkend=»catalog-pg- authid»>*pg_authid .*oid) Owner of the publication
puballtables bool If true, this publication automatically includes all tables in the database, including any that will be created in the future.
pubinsert bool If true, sql-insert operations are replicated for tables in the publication.
pubupdate bool If true, sql-update operations are replicated for tables in the publication.
pubdelete bool If true, sql-delete operations are replicated for tables in the publication.
pubtruncate bool If true, sql-truncate operations are replicated for tables in the publication.
pubviaroot bool If true, operations on a leaf partition are replicated using the identity and schema of its topmost partitioned ancestor mentioned in the publication instead of its own.

9.2.41. pg_publication_namespace

The catalog pg_publication_namespace contains the mapping between schemas and publications in the database. This is a many-to-many mapping.

pg_publication_namespace Columns

Column Type Description
oid oid Row identifier
pnpubid oid (references linkend=»catalog-pg- publication»>pg_pu blication.oid) Reference to publication
pnnspid oid (references linkend=»catalog-pg- namespace»>pg_name space.oid) Reference to schema

9.2.42. pg_publication_rel

The catalog pg_publication_rel contains the mapping between relations and publications in the database. This is a many-to-many mapping. See also view-pg-publication-tables for a more user-friendly view of this information.

pg_publication_rel Columns

Column Type Description
oid oid Row identifier
prpubid oid (references linkend=»catalog-pg- publication»>pg_pu blication.oid) Reference to publication
prrelid oid (references linkend=»catalog-pg- class»>pg_class. oid) Reference to relation
prqual pg_node_tree Expression tree (in nodeToString() representation) for the relation’s publication qualifying condition. Null if there is no publication qualifying condition.
prattrs int2vector (references linkend=»catalog-pg- attribute»>pg_attr ibute.attnum) This is an array of values that indicates which table columns are part of the publication. For example, a value of 1 3 would mean that the first and the third table columns are published. A null value indicates that all columns are published.

9.2.43. pg_range

The catalog pg_range stores information about range types. This is in addition to the types“ entries in

linkend=»catalog-pg-type»>**pg_type**.

pg_range Columns

Column Type Description
rngtypid oid (references linkend=»catalog-pg- type»>pg_type. oid) OID of the range type
rngsubtype oid (references linkend=»catalog-pg- type»>pg_type. oid) OID of the element type (subtype) of this range type
rngmultitypid oid (references linkend=»catalog-pg- type»>pg_type. oid) OID of the multirange type for this range type
rngcollation oid (references linkend=»catalog-pg- collation»>pg_coll ation.oid) OID of the collation used for range comparisons, or zero if none
rngsubopc oid (references linkend=»catalog-pg- opclass»>pg_opclas s.oid) OID of the subtype’s operator class used for range comparisons
rngcanonical regproc (references linkend=»catalog-pg- proc»>pg_proc. oid) OID of the function to convert a range value into canonical form, or zero if none
rngsubdiff regproc (references linkend=»catalog-pg- proc»>pg_proc. oid) OID of the function to return the difference between two element values as double precision, or zero if none

rngsubopc (plus rngcollation, if the element type is collatable) determines the sort ordering used by the range type. rngcanonical is used when the element type is discrete. rngsubdiff is optional but should be supplied to improve performance of GiST indexes on the range type.

9.2.44. pg_replication_origin

The pg_replication_origin catalog contains all replication origins created. For more on replication origins see replication-origins.

Unlike most system catalogs, pg_replication_origin is shared across all databases of a cluster: there is only one copy of pg_replication_origin per cluster, not one per database.

pg_replication_origin Columns

Column Type Description
roident oid A unique, cluster-wide identifier for the replication origin. Should never leave the system.
roname text The external, user defined, name of a replication origin.

9.2.45. pg_rewrite

The catalog pg_rewrite stores rewrite rules for tables and views.

pg_rewrite Columns

Column Type Description
oid oid Row identifier
rulename name Rule name
ev_class oid (references linkend=»catalog-pg- class»>pg_class. oid) The table this rule is for
ev_type char Event type that the rule is for: 1 = sql-select, 2 = sql-update, 3 = sql-insert, 4 = sql-delete
ev_enabled char Controls in which guc-session-replicat ion-role modes the rule fires. O = rule fires in origin and local modes, D = rule is disabled, R = rule fires in replica mode, A = rule fires always.
is_instead bool True if the rule is an INSTEAD rule
ev_qual pg_node_tree Expression tree (in the form of a nodeToString() representation) for the rule’s qualifying condition
ev_action pg_node_tree Query tree (in the form of a nodeToString() representation) for the rule’s action

Примечание

pg_class.relhasrules must be true if a table has any rules in this catalog.

9.2.46. pg_seclabel

The catalog pg_seclabel stores security labels on database objects. Security labels can be manipulated with the linkend=»sql-security-label»>**SECURITY LABEL** command. For an easier way to view security labels, see view-pg-seclabels.

See also linkend=»catalog-pg-shseclabel»>**pg_shseclabel**, which performs a similar function for security labels of database objects that are shared across a database cluster.

pg_seclabel Columns

Column Type Description
objoid oid (references any OID column) The OID of the object this security label pertains to
classoid oid (references linkend=»catalog-pg- class»>pg_class. oid) The OID of the system catalog this object appears in
objsubid int4 For a security label on a table column, this is the column number (the objoid and classoid refer to the table itself). For all other object types, this column is zero.
provider text The label provider associated with this label.
label text The security label applied to this object.

9.2.47. pg_sequence

The catalog pg_sequence contains information about sequences. Some of the information about sequences, such as the name and the schema, is in

linkend=»catalog-pg-class»>**pg_class**

pg_sequence Columns

Column Type Description
seqrelid oid (references linkend=»catalog-pg- class»>pg_class. oid) The OID of the linkend=»catalog-pg- class»>pg_class entry for this sequence
seqtypid oid (references linkend=»catalog-pg- type»>pg_type. oid) Data type of the sequence
seqstart int8 Start value of the sequence
seqincrement int8 Increment value of the sequence
seqmax int8 Maximum value of the sequence
seqmin int8 Minimum value of the sequence
seqcache int8 Cache size of the sequence
seqcycle bool Whether the sequence cycles

9.2.48. pg_shdepend

The catalog pg_shdepend records the dependency relationships between database objects and shared objects, such as roles. This information allows PostgreSQL to ensure that those objects are unreferenced before attempting to delete them.

See also linkend=»catalog-pg-depend»>**pg_depend**, which performs a similar function for dependencies involving objects within a single database.

Unlike most system catalogs, pg_shdepend is shared across all databases of a cluster: there is only one copy of pg_shdepend per cluster, not one per database.

pg_shdepend Columns

Column Type Description
dbid oid (references linkend=»catalog-pg- database»>pg_datab ase.oid) The OID of the database the dependent object is in, or zero for a shared object
classid oid (references linkend=»catalog-pg- class»>pg_class. oid) The OID of the system catalog the dependent object is in
objid oid (references any OID column) The OID of the specific dependent object
objsubid int4 For a table column, this is the column number (the objid and classid refer to the table itself). For all other object types, this column is zero.
refclassid oid (references linkend=»catalog-pg- class»>pg_class. oid) The OID of the system catalog the referenced object is in (must be a shared catalog)
refobjid oid (references any OID column) The OID of the specific referenced object
deptype char A code defining the specific semantics of this dependency relationship; see text

In all cases, a pg_shdepend entry indicates that the referenced object cannot be dropped without also dropping the dependent object. However, there are several subflavors identified by deptype:

The referenced object (which must be a role) is the owner of the dependent object.
The referenced object (which must be a role) is mentioned in the ACL (access control list, i.e., privileges list) of the dependent object. (A SHARED_DEPENDENCY_ACL entry is not made for the owner of the object, since the owner will have a SHARED_DEPENDENCY_OWNER entry anyway.)
The referenced object (which must be a role) is mentioned as the target of a dependent policy object.
The referenced object (which must be a tablespace) is mentioned as the tablespace for a relation that doesn’t have storage.

Other dependency flavors might be needed in future. Note in particular that the current definition only supports roles and tablespaces as referenced objects.

As in the pg_depend catalog, most objects created during initdb are considered pinned. No entries are made in pg_shdepend that would have a pinned object as either referenced or dependent object.

9.2.49. pg_shdescription

The catalog pg_shdescription stores optional descriptions (comments) for shared database objects. Descriptions can be manipulated with the linkend=»sql-comment»>**COMMENT** command and viewed with psql’s d commands.

See also linkend=»catalog-pg-description»>**pg_description**, which performs a similar function for descriptions involving objects within a single database.

Unlike most system catalogs, pg_shdescription is shared across all databases of a cluster: there is only one copy of pg_shdescription per cluster, not one per database.

pg_shdescription Columns

Column Type Description
objoid oid (references any OID column) The OID of the object this description pertains to
classoid oid (references linkend=»catalog-pg- class»>pg_class. oid) The OID of the system catalog this object appears in
description text Arbitrary text that serves as the description of this object

9.2.50. pg_shseclabel

The catalog pg_shseclabel stores security labels on shared database objects. Security labels can be manipulated with the linkend=»sql-security-label»>**SECURITY LABEL** command. For an easier way to view security labels, see view-pg-seclabels.

See also linkend=»catalog-pg-seclabel»>**pg_seclabel**, which performs a similar function for security labels involving objects within a single database.

Unlike most system catalogs, pg_shseclabel is shared across all databases of a cluster: there is only one copy of pg_shseclabel per cluster, not one per database.

pg_shseclabel Columns

Column Type Description
objoid oid (references any OID column) The OID of the object this security label pertains to
classoid oid (references linkend=»catalog-pg- class»>pg_class. oid) The OID of the system catalog this object appears in
provider text The label provider associated with this label.
label text The security label applied to this object.

9.2.51. pg_statistic

The catalog pg_statistic stores statistical data about the contents of the database. Entries are created by linkend=»sql-analyze»>**ANALYZE** and subsequently used by the query planner. Note that all the statistical data is inherently approximate, even assuming that it is up-to-date.

Normally there is one entry, with stainherit = false, for each table column that has been analyzed. If the table has inheritance children or partitions, a second entry with stainherit = true is also created. This row represents the column’s statistics over the inheritance tree, i.e., statistics for the data you’d see with SELECT column FROM table*, whereas the stainherit = false row represents the results of SELECT column FROM ONLY table.

pg_statistic also stores statistical data about the values of index expressions. These are described as if they were actual data columns; in particular, starelid references the index. No entry is made for an ordinary non-expression index column, however, since it would be redundant with the entry for the underlying table column. Currently, entries for index expressions always have stainherit = false.

Since different kinds of statistics might be appropriate for different kinds of data, pg_statistic is designed not to assume very much about what sort of statistics it stores. Only extremely general statistics (such as nullness) are given dedicated columns in pg_statistic. Everything else is stored in slots, which are groups of associated columns whose content is identified by a code number in one of the slot’s columns. For more information see src/include/catalog/pg_statistic.h.

pg_statistic should not be readable by the public, since even statistical information about a table’s contents might be considered sensitive. (Example: minimum and maximum values of a salary column might be quite interesting.)

linkend=»view-pg-stats»>**pg_stats**

is a publicly readable view on pg_statistic that only exposes information about those tables that are readable by the current user.

pg_statistic Columns

Column Type Description
starelid oid (references linkend=»catalog-pg- class»>pg_class. oid) The table or index that the described column belongs to
staattnum int2 (references linkend=»catalog-pg- attribute»>pg_attr ibute.attnum) The number of the described column
stainherit bool If true, the stats include values from child tables, not just the values in the specified relation
stanullfrac float4 The fraction of the column’s entries that are null
stawidth int4 The average stored width, in bytes, of nonnull entries
stadistinct float4 The number of distinct nonnull data values in the column. A value greater than zero is the actual number of distinct values. A value less than zero is the negative of a multiplier for the number of rows in the table; for example, a column in which about 80% of the values are nonnull and each nonnull value appears about twice on average could be represented by stadistinct = -0.4. A zero value means the number of distinct values is unknown.
stakindN int2 A code number indicating the kind of statistics stored in the Nth slot of the pg_statistic row.
staopN oid (references linkend=»catalog-pg- operator»>pg_opera tor.oid) An operator used to derive the statistics stored in the Nth slot. For example, a histogram slot would show the < operator that defines the sort order of the data. Zero if the statistics kind does not require an operator.
stacollN oid (references linkend=»catalog-pg- collation»>pg_coll ation.oid) The collation used to derive the statistics stored in the Nth slot. For example, a histogram slot for a collatable column would show the collation that defines the sort order of the data. Zero for noncollatable data.
stanumbersN float4[] Numerical statistics of the appropriate kind for the Nth slot, or null if the slot kind does not involve numerical values
stavaluesN anyarray Column data values of the appropriate kind for the Nth slot, or null if the slot kind does not store any data values. Each array’s element values are actually of the specific column’s data type, or a related type such as an array’s element type, so there is no way to define these columns“ type more specifically than anyarray.

9.2.52. pg_statistic_ext

The catalog pg_statistic_ext holds definitions of extended planner statistics. Each row in this catalog corresponds to a statistics object created with linkend=»sql-createstatistics»>**CREATE STATISTICS**.

pg_statistic_ext Columns

Column Type Description
oid oid Row identifier
stxrelid oid (references linkend=»catalog-pg- class»>pg_class. oid) Table containing the columns described by this object
stxname name Name of the statistics object
stxnamespace oid (references linkend=»catalog-pg- namespace»>pg_name space.oid) The OID of the namespace that contains this statistics object
stxowner oid (references linkend=»catalog-pg- authid»>*pg_authid .*oid) Owner of the statistics object
stxstattarget int4 stxstattarget controls the level of detail of statistics accumulated for this statistics object by linkend=»sql-analyze «>ANALYZE. A zero value indicates that no statistics should be collected. A negative value says to use the maximum of the statistics targets of the referenced columns, if set, or the system default statistics target. Positive values of stxstattarget determine the target number of most common values to collect.
stxkeys int2vector (references linkend=»catalog-pg- attribute»>pg_attr ibute.attnum) An array of attribute numbers, indicating which table columns are covered by this statistics object; for example a value of 1 3 would mean that the first and the third table columns are covered
stxkind char[] An array containing codes for the enabled statistics kinds; valid values are: d for n-distinct statistics, f for functional dependency statistics, m for most common values (MCV) list statistics, and e for expression statistics
stxexprs pg_node_tree Expression trees (in nodeToString() representation) for statistics object attributes that are not simple column references. This is a list with one element per expression. Null if all statistics object attributes are simple references.

The pg_statistic_ext entry is filled in completely during linkend=»sql-createstatistics»>**CREATE STATISTICS**, but the actual statistical values are not computed then. Subsequent linkend=»sql-analyze»>**ANALYZE** commands compute the desired values and populate an entry in the

linkend=»catalog-pg-statistic-ext-data»>**pg_statistic_ext_data**

catalog.

9.2.53. pg_statistic_ext_data

The catalog pg_statistic_ext_data holds data for extended planner statistics defined in

linkend=»catalog-pg-statistic-ext»>**pg_statistic_ext**.

Each row in this catalog corresponds to a statistics object created with linkend=»sql-createstatistics»>**CREATE STATISTICS**.

Normally there is one entry, with stxdinherit = false, for each statistics object that has been analyzed. If the table has inheritance children or partitions, a second entry with stxdinherit = true is also created. This row represents the statistics object over the inheritance tree, i.e., statistics for the data you’d see with SELECT * FROM table*, whereas the stxdinherit = false row represents the results of SELECT * FROM ONLY table.

Like linkend=»catalog-pg-statistic»>**pg_statistic**, pg_statistic_ext_data should not be readable by the public, since the contents might be considered sensitive. (Example: most common combinations of values in columns might be quite interesting.)

linkend=»view-pg-stats-ext»>**pg_stats_ext**

is a publicly readable view on pg_statistic_ext_data (after joining with linkend=»catalog-pg-statistic-ext»>**pg_statistic_ext**) that only exposes information about those tables and columns that are readable by the current user.

pg_statistic_ext_data Columns

Column Type Description
stxoid oid (references linkend=»catalog-pg- statistic-ext»>pg_ statistic_ext.oi d) Extended statistics object containing the definition for this data
stxdinherit bool If true, the stats include values from child tables, not just the values in the specified relation
stxdndistinct pg_ndistinct N-distinct counts, serialized as pg_ndistinct type
stxddependencies pg_dependencies Functional dependency statistics, serialized as pg_dependencies type
stxdmcv pg_mcv_list MCV (most-common values) list statistics, serialized as pg_mcv_list type
stxdexpr pg_statistic[] Per-expression statistics, serialized as an array of pg_statistic type

9.2.54. pg_subscription

The catalog pg_subscription contains all existing logical replication subscriptions. For more information about logical replication see logical-replication.

Unlike most system catalogs, pg_subscription is shared across all databases of a cluster: there is only one copy of pg_subscription per cluster, not one per database.

Access to the column subconninfo is revoked from normal users, because it could contain plain-text passwords.

pg_subscription Columns

Column Type Description
oid oid Row identifier
subdbid oid (references linkend=»catalog-pg- database»>pg_datab ase.oid) OID of the database that the subscription resides in
subskiplsn pg_lsn Finish LSN of the transaction whose changes are to be skipped, if a valid LSN; otherwise 0/0.
subname name Name of the subscription
subowner oid (references linkend=»catalog-pg- authid»>*pg_authid .*oid) Owner of the subscription
subenabled bool If true, the subscription is enabled and should be replicating
subbinary bool If true, the subscription will request that the publisher send data in binary format
substream bool If true, the subscription will allow streaming of in-progress transactions
subtwophasestate char State codes for two-phase mode: d = disabled, p = pending enablement, e = enabled
subdisableonerr bool If true, the subscription will be disabled if one of its workers detects an error
subconninfo text Connection string to the upstream database
subslotname name Name of the replication slot in the upstream database (also used for the local replication origin name); null represents NONE
subsynccommit text The synchronous_commit setting for the subscription’s workers to use
subpublications text[] Array of subscribed publication names. These reference publications defined in the upstream database. For more on publications see logical-replication- publication.

9.2.55. pg_subscription_rel

The catalog pg_subscription_rel contains the state for each replicated relation in each subscription. This is a many-to-many mapping.

This catalog only contains tables known to the subscription after running either linkend=»sql-createsubscription»>**CREATE SUBSCRIPTION** or

linkend=»sql-altersubscription»>**ALTER SUBSCRIPTION … REFRESH

PUBLICATION**.

pg_subscription_rel Columns

Column Type Description
srsubid oid (references linkend=»catalog-pg- subscription»>pg_s ubscription.*oid *) Reference to subscription
srrelid oid (references linkend=»catalog-pg- class»>pg_class. oid) Reference to relation
srsubstate char State code: i = initialize, d = data is being copied, f = finished table copy, s = synchronized, r = ready (normal replication)
srsublsn pg_lsn Remote LSN of the state change used for synchronization coordination when in s or r states, otherwise null

9.2.56. pg_tablespace

The catalog pg_tablespace stores information about the available tablespaces. Tables can be placed in particular tablespaces to aid administration of disk layout.

Unlike most system catalogs, pg_tablespace is shared across all databases of a cluster: there is only one copy of pg_tablespace per cluster, not one per database.

pg_tablespace Columns

Column Type Description
oid oid Row identifier
spcname name Tablespace name
spcowner oid (references linkend=»catalog-pg- authid»>*pg_authid .*oid) Owner of the tablespace, usually the user who created it
spcacl aclitem[] Access privileges; see ddl-priv for details
spcoptions text[] Tablespace-level options, as keyword=value strings

9.2.57. pg_transform

The catalog pg_transform stores information about transforms, which are a mechanism to adapt data types to procedural languages. See sql-createtransform for more information.

pg_transform Columns

Column Type Description
oid oid Row identifier
trftype oid (references linkend=»catalog-pg- type»>pg_type. oid) OID of the data type this transform is for
trflang oid (references linkend=»catalog-pg- language»>pg_langu age.oid) OID of the language this transform is for
trffromsql regproc (references linkend=»catalog-pg- proc»>pg_proc. oid) The OID of the function to use when converting the data type for input to the procedural language (e.g., function parameters). Zero is stored if the default behavior should be used.
trftosql regproc (references linkend=»catalog-pg- proc»>pg_proc. oid) The OID of the function to use when converting output from the procedural language (e.g., return values) to the data type. Zero is stored if the default behavior should be used.

9.2.58. pg_trigger

The catalog pg_trigger stores triggers on tables and views. See sql-createtrigger for more information.

pg_trigger Columns

Column Type Description
oid oid Row identifier
tgrelid oid (references linkend=»catalog-pg- class»>pg_class. oid) The table this trigger is on
tgparentid oid (references linkend=»catalog-pg- trigger»>pg_trigge r.oid) Parent trigger that this trigger is cloned from (this happens when partitions are created or attached to a partitioned table); zero if not a clone
tgname name Trigger name (must be unique among triggers of same table)
tgfoid oid (references linkend=»catalog-pg- proc»>pg_proc. oid) The function to be called
tgtype int2 Bit mask identifying trigger firing conditions
tgenabled char Controls in which guc-session-replicat ion-role modes the trigger fires. O = trigger fires in origin and local modes, D = trigger is disabled, R = trigger fires in replica mode, A = trigger fires always.
tgisinternal bool True if trigger is internally generated (usually, to enforce the constraint identified by tgconstraint)
tgconstrrelid oid (references linkend=»catalog-pg- class»>pg_class. oid) The table referenced by a referential integrity constraint (zero if trigger is not for a referential integrity constraint)
tgconstrindid oid (references linkend=»catalog-pg- class»>pg_class. oid) The index supporting a unique, primary key, referential integrity, or exclusion constraint (zero if trigger is not for one of these types of constraint)
tgconstraint oid (references linkend=»catalog-pg- constraint»>pg_con straint.oid) The linkend=»catalog-pg- constraint»>pg_con straint entry associated with the trigger (zero if trigger is not for a constraint)
tgdeferrable bool True if constraint trigger is deferrable
tginitdeferred bool True if constraint trigger is initially deferred
tgnargs int2 Number of argument strings passed to trigger function
tgattr int2vector (references linkend=»catalog-pg- attribute»>pg_attr ibute.attnum) Column numbers, if trigger is column-specific; otherwise an empty array
tgargs bytea Argument strings to pass to trigger, each NULL-terminated
tgqual pg_node_tree Expression tree (in nodeToString() representation) for the trigger’s WHEN condition, or null if none
tgoldtable name REFERENCING clause name for OLD TABLE, or null if none
tgnewtable name REFERENCING clause name for NEW TABLE, or null if none

Currently, column-specific triggering is supported only for UPDATE events, and so tgattr is relevant only for that event type. tgtype might contain bits for other event types as well, but those are presumed to be table-wide regardless of what is in tgattr.

Примечание

When tgconstraint is nonzero, tgconstrrelid, tgconstrindid, tgdeferrable, and tginitdeferred are largely redundant with the referenced linkend=»catalog-pg-constraint»>**pg_constraint** entry. However, it is possible for a non-deferrable trigger to be associated with a deferrable constraint: foreign key constraints can have some deferrable and some non-deferrable triggers.

Примечание

pg_class.relhastriggers must be true if a relation has any triggers in this catalog.

9.2.59. pg_ts_config

The pg_ts_config catalog contains entries representing text search configurations. A configuration specifies a particular text search parser and a list of dictionaries to use for each of the parser’s output token types. The parser is shown in the pg_ts_config entry, but the token-to-dictionary mapping is defined by subsidiary entries in linkend=»catalog-pg-ts-config-map»>**pg_ts_config_map**.