index 65171841c94083d073afc0b3b4e4ab5531e7c421..5aced083e9eb0d134aedf02fc7721ad485acf0dd 100644 (file)
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>