From d73f4c74dd34b19c19839f7ae09fb96442728509 Mon Sep 17 00:00:00 2001
From: Tom Lane
Date: Thu, 4 Oct 2018 15:48:17 -0400
Subject: 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
---
 src/include/executor/executor.h | 9 +++++++++
 1 file changed, 9 insertions(+)

(limited to 'src/include/executor/executor.h')

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);
-- 
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