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| author | Etsuro Fujita | 2021-05-17 08:30:00 +0000 |
|---|---|---|
| committer | Etsuro Fujita | 2021-05-17 08:30:00 +0000 |
| commit | 15fcd33e0694428d0567a6796891b759bc91e6f9 (patch) | |
| tree | 6939a78df2af80b6c0166a484952605e28b44373 | |
| parent | 07af57dbad589bbef9d7178d9b1cb354412e823f (diff) | |
Doc: Update documentation for asynchronous execution.
Add a note of caution on the performance of asynchronous execution by
postgres_fdw. Follow-up for commit 27e1f1456.
Stephen Frost, a little bit expanded by me.
Discussion: https://postgr.es/m/20210506171224.GV20766%40tamriel.snowman.net
| -rw-r--r-- | doc/src/sgml/postgres-fdw.sgml | 10 |
1 files changed, 10 insertions, 0 deletions
diff --git a/doc/src/sgml/postgres-fdw.sgml b/doc/src/sgml/postgres-fdw.sgml index 839126c4efe..fb87372bde1 100644 --- a/doc/src/sgml/postgres-fdw.sgml +++ b/doc/src/sgml/postgres-fdw.sgml @@ -401,6 +401,16 @@ OPTIONS (ADD password_required 'false'); A table-level option overrides a server-level option. The default is <literal>false</literal>. </para> + + <para> + In order to ensure that the data being returned from a foreign server + is consistent, <filename>postgres_fdw</filename> will only open one + connection for a given foreign server and will run all queries against + that server sequentially even if there are multiple foreign tables + involved, unless those tables are subject to different user mappings. + In such a case, it may be more performant to disable this option to + eliminate the overhead associated with running queries asynchronously. + </para> </listitem> </varlistentry> |