In the executor, use an array of pointers to access the rangetable.

Instead of doing a lot of list_nth() accesses to es_range_table,
create a flattened pointer array during executor startup and index
into that to get at individual RangeTblEntrys.

This eliminates one source of O(N^2) behavior with lots of partitions.
(I'm not exactly convinced that it's the most important source, but
it's an easy one to fix.)

Amit Langote and David Rowley

Discussion: https://postgr.es/m/468c85d9-540e-66a2-1dde-fec2b741e688@lab.ntt.co.jp

1 files changed, 9 insertions, 0 deletions

diff --git a/src/include/executor/executor.h b/src/include/executor/executor.h
index 83ce989e3a3..830f42dfe3c 100644
--- a/src/include/executor/executor.h
+++ b/src/include/executor/executor.h
@@ -514,6 +514,15 @@ extern bool ExecRelationIsTargetRelation(EState *estate, Index scanrelid);
 
 extern Relation ExecOpenScanRelation(EState *estate, Index scanrelid, int eflags);
 
+extern void ExecInitRangeTable(EState *estate, List *rangeTable);
+
+static inline RangeTblEntry *
+exec_rt_fetch(Index rti, EState *estate)
+{
+	Assert(rti > 0 && rti <= estate->es_range_table_size);
+	return estate->es_range_table_array[rti - 1];
+}
+
 extern Relation ExecGetRangeTableRelation(EState *estate, Index rti);
 
 extern int	executor_errposition(EState *estate, int location);