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| -rw-r--r-- | doc/src/sgml/postgres-fdw.sgml | 13 |
1 files changed, 13 insertions, 0 deletions
diff --git a/doc/src/sgml/postgres-fdw.sgml b/doc/src/sgml/postgres-fdw.sgml index 65171841c94..5aced083e9e 100644 --- a/doc/src/sgml/postgres-fdw.sgml +++ b/doc/src/sgml/postgres-fdw.sgml @@ -411,6 +411,19 @@ OPTIONS (ADD password_required 'false'); In such a case, it may be more performant to disable this option to eliminate the overhead associated with running queries asynchronously. </para> + + <para> + Asynchronous execution is applied even when an + <structname>Append</structname> node contains subplan(s) executed + synchronously as well as subplan(s) executed asynchronously. + In such a case, if the asynchronous subplans are ones processed using + <filename>postgres_fdw</filename>, tuples from the asynchronous + subplans are not returned until after at least one synchronous subplan + returns all tuples, as that subplan is executed while the asynchronous + subplans are waiting for the results of asynchronous queries sent to + foreign servers. + This behavior might change in a future release. + </para> </listitem> </varlistentry> |