From 3c821466abcdb8120ab0dfbce02f3bbae3b62025 Mon Sep 17 00:00:00 2001
From: Tom Lane <tgl@sss.pgh.pa.us>
Date: Mon, 23 Jan 2017 09:38:36 -0500
Subject: [PATCH] Fix example plan in optimizer/README.
Joining three tables only takes two join nodes. I think when I (tgl)
wrote this, I was envisioning possible additional joins; but since the
example doesn't show any fourth table, it's just confusing to write
a third join node.
Etsuro Fujita
Discussion: https://postgr.es/m/e6cfbaa3-af02-1abc-c25e-8fa5c6bc4e21@lab.ntt.co.jp
---
src/backend/optimizer/README | 5 ++---
1 file changed, 2 insertions(+), 3 deletions(-)
diff --git a/src/backend/optimizer/README b/src/backend/optimizer/README
index 7ae2b74b2c2..fc0fca41071 100644
--- a/src/backend/optimizer/README
+++ b/src/backend/optimizer/README
@@ -757,9 +757,8 @@ to create a plan like
-> Seq Scan on SmallTable1 A
NestLoop
-> Seq Scan on SmallTable2 B
- NestLoop
- -> Index Scan using XYIndex on LargeTable C
- Index Condition: C.X = A.AID and C.Y = B.BID
+ -> Index Scan using XYIndex on LargeTable C
+ Index Condition: C.X = A.AID and C.Y = B.BID
so we should be willing to pass down A.AID through a join even though
there is no join order constraint forcing the plan to look like this.
--
GitLab