diff options
| -rw-r--r-- | doc/src/sgml/indexam.sgml | 22 |
1 files changed, 19 insertions, 3 deletions
diff --git a/doc/src/sgml/indexam.sgml b/doc/src/sgml/indexam.sgml index c72c522175f..beb99d1831a 100644 --- a/doc/src/sgml/indexam.sgml +++ b/doc/src/sgml/indexam.sgml @@ -385,7 +385,8 @@ amcostestimate (PlannerInfo *root, Cost *indexStartupCost, Cost *indexTotalCost, Selectivity *indexSelectivity, - double *indexCorrelation); + double *indexCorrelation, + double *indexPages); </programlisting> Estimate the costs of an index scan. This function is described fully in <xref linkend="index-cost-estimation"/>, below. @@ -1155,7 +1156,8 @@ amcostestimate (PlannerInfo *root, Cost *indexStartupCost, Cost *indexTotalCost, Selectivity *indexSelectivity, - double *indexCorrelation); + double *indexCorrelation, + double *indexPages); </programlisting> The first three parameters are inputs: @@ -1197,7 +1199,7 @@ amcostestimate (PlannerInfo *root, </para> <para> - The last four parameters are pass-by-reference outputs: + The last five parameters are pass-by-reference outputs: <variablelist> <varlistentry> @@ -1236,6 +1238,15 @@ amcostestimate (PlannerInfo *root, </para> </listitem> </varlistentry> + + <varlistentry> + <term><parameter>*indexPages</parameter></term> + <listitem> + <para> + Set to number of index leaf pages + </para> + </listitem> + </varlistentry> </variablelist> </para> @@ -1284,6 +1295,11 @@ amcostestimate (PlannerInfo *root, </para> <para> + The <parameter>indexPages</parameter> should be set to the number of leaf pages. + This is used to estimate the number of workers for parallel index scan. + </para> + + <para> When <parameter>loop_count</parameter> is greater than one, the returned numbers should be averages expected for any one scan of the index. </para> |