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Tantor Special Edition 15.12 documentation

Table of contents:

  • Preface
    • 1.  What Is Tantor SE?
    • 2. A Brief History of PostgreSQL
    • 3. What are the differences between Tantor SE 15 and PostgreSQL 15
    • 4. Conventions
    • 5. Bug Reporting Guidelines
  • Part I. Tutorial
    • Chapter 1. Synopsis
    • Chapter 2. The SQL Language
    • Chapter 3. Advanced Features
  • Part II. The SQL Language
    • Chapter 4. SQL Syntax
    • Chapter 5. Data Definition
    • Chapter 6. Data Manipulation
    • Chapter 7. Queries
    • Chapter 8. Data Types
    • Chapter 9. Functions and Operators
    • Chapter 10. Type Conversion
    • Chapter 11. Indexes
    • Chapter 12. Full Text Search
    • Chapter 13. Concurrency Control
    • Chapter 14. Performance Tips
    • Chapter 15. Parallel Query
    • Chapter 16. Autonomous Transactions
  • Part III. Server Administration
    • Chapter 17. Installation from Binaries
    • Chapter 18. Server Setup and Operation
    • Chapter 19. Server Configuration
    • Chapter 20. Client Authentication
    • Chapter 21. Database Roles
    • Chapter 22. Managing Databases
    • Chapter 23. Localization
    • Chapter 24. Routine Database Maintenance Tasks
    • Chapter 25. Backup and Restore
    • Chapter 26. High Availability, Load Balancing, and Replication
    • Chapter 27. Monitoring Database Activity
    • Chapter 28. Monitoring Disk Usage
    • Chapter 29. Reliability and the Write-Ahead Log
    • Chapter 30. Logical Replication
    • Chapter 31. Just-in-Time Compilation (JIT)
  • Part IV. Client Interfaces
    • Chapter 32. libpq — C Library
    • Chapter 33. Large Objects
    • Chapter 34. ECPG — Embedded SQL in C
    • Chapter 35. The Information Schema
  • Part V. Server Programming
    • Chapter 36. Extending SQL
    • Chapter 37. Triggers
    • Chapter 38. Event Triggers
    • Chapter 39. The Rule System
    • Chapter 40. Procedural Languages
    • Chapter 41. PL/pgSQL — SQL Procedural Language
    • Chapter 42. PL/Tcl — Tcl Procedural Language
    • Chapter 43. PL/Perl — Perl Procedural Language
    • Chapter 44. PL/Python — Python Procedural Language
    • Chapter 45. Server Programming Interface
    • Chapter 46. Background Worker Processes
    • Chapter 47. Logical Decoding
    • Chapter 48. Replication Progress Tracking
    • Chapter 49. Archive Modules
  • Part VI. Reference
    • SQL Commands
    • PostgreSQL Client Applications
    • PostgreSQL Server Applications
  • Part VII. Internals
    • Chapter 50. Overview of PostgreSQL Internals
    • Chapter 51. System Catalogs
    • Chapter 52. System Views
    • Chapter 53. Frontend/Backend Protocol
    • Chapter 54. PostgreSQL Coding Conventions
    • Chapter 55. Native Language Support
    • Chapter 56. Writing a Procedural Language Handler
    • Chapter 57. Writing a Foreign Data Wrapper
    • Chapter 58. Writing a Table Sampling Method
    • Chapter 59. Writing a Custom Scan Provider
    • Chapter 60. Genetic Query Optimizer
    • Chapter 61. Table Access Method Interface Definition
    • Chapter 62. Index Access Method Interface Definition
    • Chapter 63. Generic WAL Records
    • Chapter 64. Custom WAL Resource Managers
    • Chapter 65. B-Tree Indexes
    • Chapter 66. GiST Indexes
    • Chapter 67. SP-GiST Indexes
    • Chapter 68. GIN Indexes
    • Chapter 69. BRIN Indexes
    • Chapter 70. Hash Indexes
    • Chapter 71. Database Physical Storage
    • Chapter 72. System Catalog Declarations and Initial Contents
    • Chapter 73. How the Planner Uses Statistics
    • Chapter 74. Backup Manifest Format
  • Part VIII. Appendixes
    • Appendix A. Tantor SE Error Codes
    • Appendix B. Date/Time Support
    • Appendix C. SQL Key Words
    • Appendix D. SQL Conformance
    • Appendix E. Release Notes
    • Appendix F. Additional Supplied Modules
    • Appendix G. Additional Supplied Programs
    • Appendix H. Additional External Modules
    • Appendix I. External Projects
    • Appendix J. Tantor SE Limits
    • Appendix K. Acronyms
    • Appendix L. Glossary
    • Appendix M. Color Support
    • Appendix N. Obsolete or Renamed Features
  • Bibliography
  • Index

dblink_get_result

dblink_get_result#

dblink_get_result
dblink_get_result
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dblink_get_result

dblink_get_result — gets an async query result

Synopsis

dblink_get_result(text connname [, bool fail_on_error]) returns setof record

Description

dblink_get_result collects the results of an asynchronous query previously sent with dblink_send_query. If the query is not already completed, dblink_get_result will wait until it is.

Arguments

connname

Name of the connection to use.

fail_on_error

If true (the default when omitted) then an error thrown on the remote side of the connection causes an error to also be thrown locally. If false, the remote error is locally reported as a NOTICE, and the function returns no rows.

Return Value

For an async query (that is, an SQL statement returning rows), the function returns the row(s) produced by the query. To use this function, you will need to specify the expected set of columns, as previously discussed for dblink.

For an async command (that is, an SQL statement not returning rows), the function returns a single row with a single text column containing the command's status string. It is still necessary to specify that the result will have a single text column in the calling FROM clause.

Notes

This function must be called if dblink_send_query returned 1. It must be called once for each query sent, and one additional time to obtain an empty set result, before the connection can be used again.

When using dblink_send_query and dblink_get_result, dblink fetches the entire remote query result before returning any of it to the local query processor. If the query returns a large number of rows, this can result in transient memory bloat in the local session. It may be better to open such a query as a cursor with dblink_open and then fetch a manageable number of rows at a time. Alternatively, use plain dblink(), which avoids memory bloat by spooling large result sets to disk.

Examples

contrib_regression=# SELECT dblink_connect('dtest1', 'dbname=contrib_regression');
 dblink_connect
----------------
 OK
(1 row)

contrib_regression=# SELECT * FROM
contrib_regression-# dblink_send_query('dtest1', 'select * from foo where f1 < 3') AS t1;
 t1
----
  1
(1 row)

contrib_regression=# SELECT * FROM dblink_get_result('dtest1') AS t1(f1 int, f2 text, f3 text[]);
 f1 | f2 |     f3
----+----+------------
  0 | a  | {a0,b0,c0}
  1 | b  | {a1,b1,c1}
  2 | c  | {a2,b2,c2}
(3 rows)

contrib_regression=# SELECT * FROM dblink_get_result('dtest1') AS t1(f1 int, f2 text, f3 text[]);
 f1 | f2 | f3
----+----+----
(0 rows)

contrib_regression=# SELECT * FROM
contrib_regression-# dblink_send_query('dtest1', 'select * from foo where f1 < 3; select * from foo where f1 > 6') AS t1;
 t1
----
  1
(1 row)

contrib_regression=# SELECT * FROM dblink_get_result('dtest1') AS t1(f1 int, f2 text, f3 text[]);
 f1 | f2 |     f3
----+----+------------
  0 | a  | {a0,b0,c0}
  1 | b  | {a1,b1,c1}
  2 | c  | {a2,b2,c2}
(3 rows)

contrib_regression=# SELECT * FROM dblink_get_result('dtest1') AS t1(f1 int, f2 text, f3 text[]);
 f1 | f2 |      f3
----+----+---------------
  7 | h  | {a7,b7,c7}
  8 | i  | {a8,b8,c8}
  9 | j  | {a9,b9,c9}
 10 | k  | {a10,b10,c10}
(4 rows)

contrib_regression=# SELECT * FROM dblink_get_result('dtest1') AS t1(f1 int, f2 text, f3 text[]);
 f1 | f2 | f3
----+----+----
(0 rows)

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15.12.0 - 3069e28c - 2025-04-10 15:18:39