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Diffstat (limited to 'doc/src')
| -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 a90983cb1e9..c408ba659bc 100644 --- a/doc/src/sgml/postgres-fdw.sgml +++ b/doc/src/sgml/postgres-fdw.sgml @@ -487,6 +487,16 @@ </para> <para> + When <filename>postgres_fdw</> encounters a join between foreign tables on + the same foreign server, it sends the entire join to the foreign server, + unless for some reason it believes that it will be more efficient to fetch + rows from each table individually, or unless the table references involved + are subject to different user mappings. While sending the <literal>JOIN</> + clauses, it takes the same precautions as mentioned above for the + <literal>WHERE</> clauses. + </para> + + <para> The query that is actually sent to the remote server for execution can be examined using <command>EXPLAIN VERBOSE</>. </para> |