10.132. pg_walinspect
The pg_walinspect module provides SQL functions that allow you to inspect the contents of write-ahead log of a running PostgreSQL database cluster at a low level, which is useful for debugging or analytical or reporting or educational purposes. It is similar to pgwaldump, but accessible through SQL rather than a separate utility.
All the functions of this module will provide the WAL information using the current server’s timeline ID.
All the functions of this module will try to find the first valid WAL record that is at or after the given in_lsn or start_lsn and will emit error if no such record is available. Similarly, the end_lsn must be available, and if it falls in the middle of a record, the entire record must be available.
Примечание
Some functions, such as ** linkend=»pg-logical-emit-message»>pg_logical_emit_message**, return the LSN after the record just inserted. Therefore, if you pass that LSN as in_lsn or start_lsn to one of these functions, it will return the next record.
By default, use of these functions is restricted to superusers and members of the pg_read_server_files role. Access may be granted by superusers to others using GRANT.
10.132.1. General Functions
Gets WAL record information of a given LSN. If the given LSN isn’t at the start of a WAL record, it gives the information of the next available valid WAL record; or an error if no such record is found.
Gets information of all the valid WAL records between start_lsn and end_lsn. Returns one row per WAL record. If start_lsn or end_lsn are not yet available, the function will raise an error. For example, usage of the function is as follows:
postgres=# select start_lsn, end_lsn, prev_lsn, xid, resource_manager, record_type, record_length, main_data_length, fpi_length, description from pg_get_wal_records_info('0/14F9A30', '0/15011D7'); start_lsn | end_lsn | prev_lsn | xid | resource_manager | record_type | record_length | main_data_length | fpi_length | description -----------+-----------+-----------+-----+------------------+--------------+---------------+------------------+------------+--------------------- 0/14FA118 | 0/14FB4B0 | 0/14F9958 | 725 | Btree | INSERT_LEAF | 5013 | 2 | 4960 | off 246 0/14FB4B0 | 0/14FD050 | 0/14FA118 | 725 | Btree | INSERT_LEAF | 7045 | 2 | 6992 | off 130 0/14FD050 | 0/14FD0A8 | 0/14FB4B0 | 725 | Heap2 | MULTI_INSERT | 85 | 6 | 0 | 1 tuples flags 0x02 0/14FD0A8 | 0/14FD0F0 | 0/14FD050 | 725 | Btree | INSERT_LEAF | 72 | 2 | 0 | off 155 0/14FD0F0 | 0/14FD138 | 0/14FD0A8 | 725 | Btree | INSERT_LEAF | 72 | 2 | 0 | off 134 0/14FD138 | 0/14FD210 | 0/14FD0F0 | 725 | Heap | INSERT | 211 | 3 | 0 | off 11 flags 0x00 0/14FD210 | 0/14FD250 | 0/14FD138 | 725 | Btree | INSERT_LEAF | 64 | 2 | 0 | off 246 0/14FD250 | 0/14FF260 | 0/14FD210 | 725 | Btree | INSERT_LEAF | 8181 | 2 | 8128 | off 47 0/14FF260 | 0/14FF2B8 | 0/14FD250 | 725 | Heap2 | MULTI_INSERT | 85 | 6 | 0 | 1 tuples flags 0x02 0/14FF2B8 | 0/14FF300 | 0/14FF260 | 725 | Btree | INSERT_LEAF | 72 | 2 | 0 | off 155 0/14FF300 | 0/15008D8 | 0/14FF2B8 | 725 | Btree | INSERT_LEAF | 5565 | 2 | 5512 | off 106 0/15008D8 | 0/1500C48 | 0/14FF300 | 725 | Heap | INSERT | 874 | 3 | 820 | off 2 flags 0x01 (12 rows)
This function is same as pg_get_wal_records_info() except that it gets information of all the valid WAL records from start_lsn till the end of WAL.
Gets statistics of all the valid WAL records between start_lsn and end_lsn. By default, it returns one row per resource_manager type. When per_record is set to true, it returns one row per record_type. If start_lsn or end_lsn are not yet available, the function will raise an error. For example, usage of the function is as follows:
postgres=# select * from pg_get_wal_stats('0/12FBA30', '0/15011D7') where count > 0; resource_manager/record_type | count | count_percentage | record_size | record_size_percentage | fpi_size | fpi_size_percentage | combined_size | combined_size_percentage ------------------------------+-------+------------------+-------------+------------------------+----------+---------------------+---------------+-------------------------- XLOG | 10 | 0.10871929 | 796 | 0.052369177 | 352 | 0.061031006 | 1148 | 0.054751817 Transaction | 187 | 2.0330508 | 62773 | 4.1298623 | 0 | 0 | 62773 | 2.9938467 Storage | 13 | 0.14133507 | 546 | 0.035921574 | 0 | 0 | 546 | 0.0260405 Database | 2 | 0.021743858 | 84 | 0.005526396 | 0 | 0 | 84 | 0.0040062307 Standby | 218 | 2.3700805 | 15908 | 1.0465941 | 0 | 0 | 15908 | 0.75870377 Heap2 | 1897 | 20.624048 | 383916 | 25.257998 | 364472 | 63.193447 | 748388 | 35.693035 Heap | 1318 | 14.329202 | 621390 | 40.88151 | 139660 | 24.214746 | 761050 | 36.29693 Btree | 5553 | 60.37182 | 434565 | 28.590216 | 72272 | 12.530776 | 506837 | 24.17269 (8 rows)
With per_record passed as true:
postgres=# select * from pg_get_wal_stats('0/14AFC30', '0/15011D7', true) where count > 0; resource_manager/record_type | count | count_percentage | record_size | record_size_percentage | fpi_size | fpi_size_percentage | combined_size | combined_size_percentage ------------------------------+-------+------------------+-------------+------------------------+----------+---------------------+---------------+-------------------------- XLOG/CHECKPOINT_SHUTDOWN | 1 | 0.32894737 | 114 | 0.22891566 | 0 | 0 | 114 | 0.03534489 XLOG/CHECKPOINT_ONLINE | 4 | 1.3157895 | 456 | 0.91566265 | 0 | 0 | 456 | 0.14137957 XLOG/NEXTOID | 1 | 0.32894737 | 30 | 0.060240965 | 0 | 0 | 30 | 0.009301287 Transaction/COMMIT | 9 | 2.9605262 | 1173 | 2.3554218 | 0 | 0 | 1173 | 0.36368033 Storage/CREATE | 1 | 0.32894737 | 42 | 0.084337346 | 0 | 0 | 42 | 0.0130218025 Database/CREATE_FILE_COPY | 2 | 0.65789473 | 84 | 0.16867469 | 0 | 0 | 84 | 0.026043605 Standby/RUNNING_XACTS | 6 | 1.9736842 | 316 | 0.6345382 | 0 | 0 | 316 | 0.09797356 Standby/INVALIDATIONS | 45 | 14.802631 | 4018 | 8.068274 | 0 | 0 | 4018 | 1.2457525 Heap2/PRUNE | 4 | 1.3157895 | 270 | 0.5421687 | 0 | 0 | 270 | 0.08371159 Heap2/FREEZE_PAGE | 27 | 8.881579 | 20904 | 41.975903 | 0 | 0 | 20904 | 6.481137 Heap2/VISIBLE | 29 | 9.539474 | 1756 | 3.5261045 | 73728 | 27.032736 | 75484 | 23.403278 Heap2/MULTI_INSERT | 13 | 4.2763157 | 1049 | 2.1064258 | 12216 | 4.479057 | 13265 | 4.112719 Heap/INSERT | 19 | 6.25 | 2324 | 4.6666665 | 43884 | 16.090284 | 46208 | 14.326463 Heap/UPDATE | 7 | 2.3026316 | 511 | 1.0261045 | 54340 | 19.924028 | 54851 | 17.006165 Heap/HOT_UPDATE | 11 | 3.618421 | 1134 | 2.2771084 | 468 | 0.17159452 | 1602 | 0.49668875 Heap/LOCK | 8 | 2.631579 | 432 | 0.8674699 | 0 | 0 | 432 | 0.13393854 Heap/INPLACE | 45 | 14.802631 | 9123 | 18.319277 | 16076 | 5.894345 | 25199 | 7.8127713 Heap/UPDATE+INIT | 1 | 0.32894737 | 817 | 1.6405623 | 0 | 0 | 817 | 0.25330505 Btree/INSERT_LEAF | 70 | 23.026316 | 5183 | 10.407631 | 72024 | 26.407955 | 77207 | 23.937483 Btree/DEDUP | 1 | 0.32894737 | 64 | 0.12851405 | 0 | 0 | 64 | 0.019842746 (20 rows)
This function is same as pg_get_wal_stats() except that it gets statistics of all the valid WAL records from start_lsn till end of WAL.