diff options
Diffstat (limited to 'doc/src')
| -rw-r--r-- | doc/src/sgml/indexam.sgml | 26 |
1 files changed, 25 insertions, 1 deletions
diff --git a/doc/src/sgml/indexam.sgml b/doc/src/sgml/indexam.sgml index 4bf14ba7e60..a001cd4e33a 100644 --- a/doc/src/sgml/indexam.sgml +++ b/doc/src/sgml/indexam.sgml @@ -1,4 +1,4 @@ -<!-- $PostgreSQL: pgsql/doc/src/sgml/indexam.sgml,v 2.13 2006/06/05 02:49:58 tgl Exp $ --> +<!-- $PostgreSQL: pgsql/doc/src/sgml/indexam.sgml,v 2.14 2006/06/06 17:59:57 tgl Exp $ --> <chapter id="indexam"> <title>Index Access Method Interface Definition</title> @@ -344,6 +344,7 @@ void amcostestimate (PlannerInfo *root, IndexOptInfo *index, List *indexQuals, + RelOptInfo *outer_rel, Cost *indexStartupCost, Cost *indexTotalCost, Selectivity *indexSelectivity, @@ -681,6 +682,7 @@ void amcostestimate (PlannerInfo *root, IndexOptInfo *index, List *indexQuals, + RelOptInfo *outer_rel, Cost *indexStartupCost, Cost *indexTotalCost, Selectivity *indexSelectivity, @@ -718,6 +720,20 @@ amcostestimate (PlannerInfo *root, </para> </listitem> </varlistentry> + + <varlistentry> + <term>outer_rel</term> + <listitem> + <para> + If the index is being considered for use in a join inner indexscan, + the planner's information about the outer side of the join. Otherwise + NULL. When non-NULL, some of the qual clauses will be join clauses + with this rel rather than being simple restriction clauses. Also, + the cost estimator should expect that the index scan will be repeated + for each row of the outer rel. + </para> + </listitem> + </varlistentry> </variablelist> </para> @@ -808,6 +824,11 @@ amcostestimate (PlannerInfo *root, table. </para> + <para> + In the join case, the returned numbers should be averages expected for + any one scan of the index. + </para> + <procedure> <title>Cost Estimation</title> <para> @@ -859,6 +880,9 @@ amcostestimate (PlannerInfo *root, *indexTotalCost = seq_page_cost * numIndexPages + (cpu_index_tuple_cost + index_qual_cost.per_tuple) * numIndexTuples; </programlisting> + + However, the above does not account for amortization of index reads + across repeated index scans in the join case. </para> </step> |