diff options
Diffstat (limited to 'doc/src')
| -rw-r--r-- | doc/src/sgml/fdwhandler.sgml | 28 |
1 files changed, 15 insertions, 13 deletions
diff --git a/doc/src/sgml/fdwhandler.sgml b/doc/src/sgml/fdwhandler.sgml index 8e7525ab596..2c75b80b303 100644 --- a/doc/src/sgml/fdwhandler.sgml +++ b/doc/src/sgml/fdwhandler.sgml @@ -279,15 +279,19 @@ EndForeignScan (ForeignScanState *node); <para> <programlisting> -AcquireSampleRowsFunc -AnalyzeForeignTable (Relation relation); +bool +AnalyzeForeignTable (Relation relation, + AcquireSampleRowsFunc *func, + BlockNumber *totalpages); </programlisting> This function is called when <xref linkend="sql-analyze"> is executed on - a foreign table. If the FDW supports collecting statistics for this - foreign table, it should return a pointer to a function that will collect - sample rows from the table. Otherwise, return <literal>NULL</>. If the - FDW does not support collecting statistics for any tables, the + a foreign table. If the FDW can collect statistics for this + foreign table, it should return <literal>true</>, and provide a pointer + to a function that will collect sample rows from the table in + <parameter>func</>, plus the estimated size of the table in pages in + <parameter>totalpages</>. Otherwise, return <literal>false</>. + If the FDW does not support collecting statistics for any tables, the <function>AnalyzeForeignTable</> pointer can be set to <literal>NULL</>. </para> @@ -298,18 +302,16 @@ int AcquireSampleRowsFunc (Relation relation, int elevel, HeapTuple *rows, int targrows, double *totalrows, - double *totaldeadrows, - BlockNumber *totalpages); + double *totaldeadrows); </programlisting> A random sample of up to <parameter>targrows</> rows should be collected from the table and stored into the caller-provided <parameter>rows</> array. The actual number of rows collected must be returned. In - addition, store estimates of the total numbers of live rows, dead rows, - and pages in the table into the output parameters - <parameter>totalrows</>, <parameter>totaldeadrows</>, and - <parameter>totalpages</>. These numbers will be recorded in the table's - <structname>pg_class</> entry for future use. + addition, store estimates of the total numbers of live and dead rows in + the table into the output parameters <parameter>totalrows</> and + <parameter>totaldeadrows</>. (Set <parameter>totaldeadrows</> to zero + if the FDW does not have any concept of dead rows.) </para> <para> |