diff options
| -rw-r--r-- | doc/src/sgml/postgres-fdw.sgml | 40 |
1 files changed, 22 insertions, 18 deletions
diff --git a/doc/src/sgml/postgres-fdw.sgml b/doc/src/sgml/postgres-fdw.sgml index b43d0aecbac..68362fd1604 100644 --- a/doc/src/sgml/postgres-fdw.sgml +++ b/doc/src/sgml/postgres-fdw.sgml @@ -460,10 +460,16 @@ OPTIONS (ADD password_required 'false'); <title>Transaction Management Options</title> <para> - When multiple remote (sub)transactions are involved in a local - (sub)transaction, by default <filename>postgres_fdw</filename> commits - those remote (sub)transactions one by one when the local (sub)transaction - commits. + As described in the Transaction Management section, in + <filename>postgres_fdw</filename> transactions are managed by creating + corresponding remote transactions, and subtransactions are managed by + creating corresponding remote subtransactions. When multiple remote + transactions are involved in the current local transaction, by default + <filename>postgres_fdw</filename> commits those remote transactions + serially when the local transaction is committed. When multiple remote + subtransactions are involved in the current local subtransaction, by + default <filename>postgres_fdw</filename> commits those remote + subtransactions serially when the local subtransaction is committed. Performance can be improved with the following option: </para> @@ -474,26 +480,24 @@ OPTIONS (ADD password_required 'false'); <listitem> <para> This option controls whether <filename>postgres_fdw</filename> commits - remote (sub)transactions opened on a foreign server in a local - (sub)transaction in parallel when the local (sub)transaction commits. - This option can only be specified for foreign servers, not per-table. - The default is <literal>false</literal>. + in parallel remote transactions opened on a foreign server in a local + transaction when the local transaction is committed. This setting also + applies to remote and local subtransactions. This option can only be + specified for foreign servers, not per-table. The default is + <literal>false</literal>. </para> <para> - If multiple foreign servers with this option enabled are involved in - a local (sub)transaction, multiple remote (sub)transactions opened on - those foreign servers in the local (sub)transaction are committed in - parallel across those foreign servers when the local (sub)transaction - commits. + If multiple foreign servers with this option enabled are involved in a + local transaction, multiple remote transactions on those foreign + servers are committed in parallel across those foreign servers when + the local transaction is committed. </para> <para> - For a foreign server with this option enabled, if many remote - (sub)transactions are opened on the foreign server in a local - (sub)transaction, this option might increase the remote server's load - when the local (sub)transaction commits, so be careful when using this - option. + When this option is enabled, a foreign server with many remote + transactions may see a negative performance impact when the local + transaction is committed. </para> </listitem> </varlistentry> |