Date: Wed, 13 Nov 2019 14:41:14 +0100
From: Tomas Vondra <tomas.vondra@2ndquadrant.com>
To: tuomas.leikola@gmail.com, pgsql-bugs@lists.postgresql.org
Subject: Re: BUG #16111: Unexpected query compilation error =?utf-8?B?4oCc?=
 =?utf-8?Q?negative_bitmapset_member_not_allowed=E2=80=9D?=
Message-ID: <20191113134114.rxcli5c6zjmryvf6@development>
References: <16111-687799584c3a7e73@postgresql.org>
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On Wed, Nov 13, 2019 at 10:42:32AM +0000, PG Bug reporting form wrote:
>The following bug has been logged on the website:
>
>Bug reference:      16111
>Logged by:          Tuomas Leikola
>Email address:      tuomas.leikola@gmail.com
>PostgreSQL version: 12.0
>Operating system:   windows, linux
>Description:
>
>I’ve been trying to cook up some kind of online reorganizer, which requires
>looking at rows’ physical locations and rearranging those that are
>suboptimal. In this endeavor, I stumbled on what appears to be a compiler
>bug introduced with multivariate statistics.
>

Yeah, this is a bug in estimate_multivariate_ndistinct, which fails to
ignore system attributes :-(

The attached patch fixes it, but unfortunatly we've missed this round of
minor releases :-( I'll get it pushed in a couple of days.

Thanks for the report and the reproducer, very helpful!

regards

-- 
Tomas Vondra                  http://www.2ndQuadrant.com
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services

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	filename="estimate_multivariate_ndistinct.patch"

diff --git a/src/backend/utils/adt/selfuncs.c b/src/backend/utils/adt/selfuncs.c
index 8dddc5eb93..a3cccc455f 100644
--- a/src/backend/utils/adt/selfuncs.c
+++ b/src/backend/utils/adt/selfuncs.c
@@ -3592,15 +3592,21 @@ estimate_multivariate_ndistinct(PlannerInfo *root, RelOptInfo *rel,
 	/* Determine the attnums we're looking for */
 	foreach(lc, *varinfos)
 	{
+		Var			 *var;
 		GroupVarInfo *varinfo = (GroupVarInfo *) lfirst(lc);
 
 		Assert(varinfo->rel == rel);
 
-		if (IsA(varinfo->var, Var))
-		{
-			attnums = bms_add_member(attnums,
-									 ((Var *) varinfo->var)->varattno);
-		}
+		if (!IsA(varinfo->var, Var))
+			continue;
+
+		var = (Var *) varinfo->var;
+
+		if (!AttrNumberIsForUserDefinedAttr(var->varattno))
+			continue;
+
+		attnums = bms_add_member(attnums,
+								 ((Var *) varinfo->var)->varattno);
 	}
 
 	/* look for the ndistinct statistics matching the most vars */

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