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Re: BUG #5673: Optimizer creates strange execution plan leading to wrong results

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: David Schmitt <david(at)dasz(dot)at>
Cc: pgsql-bugs(at)postgresql(dot)org
Subject: Re: BUG #5673: Optimizer creates strange execution plan leading to wrong results
Date: 2010-09-23 19:53:19
Message-ID: 1782.1285271599@sss.pgh.pa.us (view raw or flat)
Thread:
Lists: pgsql-bugs
David Schmitt <david(at)dasz(dot)at> writes:
> Executing the attached example.sql on a fresh database demonstrates the 
> problem I'm seeing:

Found it.  If you need a patch right away, it's a one-liner:

diff --git a/src/backend/optimizer/path/allpaths.c b/src/backend/optimizer/path/allpaths.c
index 2d86da3..b7cf0b8 100644
--- a/src/backend/optimizer/path/allpaths.c
+++ b/src/backend/optimizer/path/allpaths.c
@@ -425,7 +425,7 @@ set_append_rel_pathlist(PlannerInfo *root, RelOptInfo *rel,
 		childpath = childrel->cheapest_total_path;
 		if (IsA(childpath, AppendPath))
 			subpaths = list_concat(subpaths,
-								   ((AppendPath *) childpath)->subpaths);
+							list_copy(((AppendPath *) childpath)->subpaths));
 		else
 			subpaths = lappend(subpaths, childpath);
 

			regards, tom lane

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