From: | Daniel Gustafsson <daniel(at)yesql(dot)se> |
---|---|
To: | Dmitry Dolgov <9erthalion6(at)gmail(dot)com> |
Cc: | Manuel Rigger <rigger(dot)manuel(at)gmail(dot)com>, PostgreSQL mailing lists <pgsql-bugs(at)lists(dot)postgresql(dot)org> |
Subject: | Re: Failed assertion clauses != NIL |
Date: | 2019-11-19 13:45:54 |
Message-ID: | 520C6E76-53A5-4EF2-A855-8054582221A5@yesql.se |
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Lists: | pgsql-bugs |
> On 19 Nov 2019, at 14:38, Dmitry Dolgov <9erthalion6(at)gmail(dot)com> wrote:
>
>> On Tue, Nov 19, 2019 at 01:50:51PM +0100, Manuel Rigger wrote:
>>
>> when building PostgreSQL with -enable-cassert, executing the following
>> statements result in an assertion error:
>>
>> CREATE TABLE t0(c0 boolean, c1 boolean, c2 boolean);
>> INSERT INTO t0 VALUES(FALSE, FALSE, FALSE);
>> CREATE STATISTICS s0 ON c0, c2 FROM t0;
>> ANALYZE;
>> SELECT * FROM t0 WHERE t0.c2 OR t0.c1 OR t0.c0;
>
> Yes, I can reproduce it too. mcv_get_match_bitmap expects that
> stat_clauses will not be empty, but looks like in this situation
> stat_clauses is indeed NIL. clauselist_selectivity_simple right before
> actually doesn't insist on stat_clauses being non empty, probably it's
> just too strict assert.
I might be missing something, but if the clause list is NIL, wouldn't it better
to exit earlier from statext_mcv_clauselist_selectivity rather than relax the
Assertion since we will get a 1.0 estimate either way?
cheers ./daniel
--- a/src/backend/statistics/extended_stats.c
+++ b/src/backend/statistics/extended_stats.c
@@ -1267,6 +1267,9 @@ statext_mcv_clauselist_selectivity(PlannerInfo *root, List *clauses, int varReli
listidx++;
}
+ if (stat_clauses == NIL)
+ return 1.0;
+
/*
* First compute "simple" selectivity, i.e. without the extended
* statistics, and essentially assuming independence of the
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