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Properly initialize SortSupport for ORDER BY rechecks in nodeIndexscan.c. 

Fix still another bug in commit 35fcb1b3d: it failed to fully initialize
the SortSupport states it introduced to allow the executor to re-check
ORDER BY expressions containing distance operators.  That led to a null
pointer dereference if the sortsupport code tried to use ssup_cxt.  The
problem only manifests in narrow cases, explaining the lack of previous
field reports.  It requires a GiST-indexable distance operator that lacks
SortSupport and is on a pass-by-ref data type, which among core+contrib
seems to be only btree_gist's interval opclass; and it requires the scan
to be done as an IndexScan not an IndexOnlyScan, which explains how
btree_gist's regression test didn't catch it.  Per bug #14134 from
Jihyun Yu.

Peter Geoghegan

Report: <20160511154904.2603.43889@wrigleys.postgresql.org>
This commit is contained in:
Tom Lane 2016-06-05 11:53:06 -04:00
parent de33af8823
commit 8a859691d5
3 changed files with 37 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

18
contrib/btree_gist/expected/interval.out
View File

@ -89,3 +89,21 @@ SELECT a, a <-> '199 days 21:21:23' FROM intervaltmp ORDER BY a <-> '199 days 21
@ 220 days 19 hours 5 mins 42 secs | @ 21 days -2 hours -15 mins -41 secs
(3 rows)
SET enable_indexonlyscan=off;
EXPLAIN (COSTS OFF)
SELECT a, a <-> '199 days 21:21:23' FROM intervaltmp ORDER BY a <-> '199 days 21:21:23' LIMIT 3;
QUERY PLAN
---------------------------------------------------------------------------
Limit
-> Index Scan using intervalidx on intervaltmp
Order By: (a <-> '@ 199 days 21 hours 21 mins 23 secs'::interval)
(3 rows)
SELECT a, a <-> '199 days 21:21:23' FROM intervaltmp ORDER BY a <-> '199 days 21:21:23' LIMIT 3;
a | ?column?
-------------------------------------+--------------------------------------
@ 199 days 21 hours 21 mins 23 secs | @ 0
@ 183 days 6 hours 52 mins 48 secs | @ 16 days 14 hours 28 mins 35 secs
@ 220 days 19 hours 5 mins 42 secs | @ 21 days -2 hours -15 mins -41 secs
(3 rows)

6
contrib/btree_gist/sql/interval.sql
View File

@ -35,3 +35,9 @@ SELECT count(*) FROM intervaltmp WHERE a > '199 days 21:21:23'::interval;
EXPLAIN (COSTS OFF)
SELECT a, a <-> '199 days 21:21:23' FROM intervaltmp ORDER BY a <-> '199 days 21:21:23' LIMIT 3;
SELECT a, a <-> '199 days 21:21:23' FROM intervaltmp ORDER BY a <-> '199 days 21:21:23' LIMIT 3;
SET enable_indexonlyscan=off;
EXPLAIN (COSTS OFF)
SELECT a, a <-> '199 days 21:21:23' FROM intervaltmp ORDER BY a <-> '199 days 21:21:23' LIMIT 3;
SELECT a, a <-> '199 days 21:21:23' FROM intervaltmp ORDER BY a <-> '199 days 21:21:23' LIMIT 3;

15
src/backend/executor/nodeIndexscan.c
View File

@ -967,9 +967,20 @@ ExecInitIndexScan(IndexScan *node, EState *estate, int eflags)
Oid orderbyop = lfirst_oid(lco);
Node *orderbyexpr = (Node *) lfirst(lcx);
Oid orderbyType = exprType(orderbyexpr);
Oid orderbyColl = exprCollation(orderbyexpr);
SortSupport orderbysort = &indexstate->iss_SortSupport[i];
/* Initialize sort support */
orderbysort->ssup_cxt = CurrentMemoryContext;
orderbysort->ssup_collation = orderbyColl;
/* See cmp_orderbyvals() comments on NULLS LAST */
orderbysort->ssup_nulls_first = false;
/* ssup_attno is unused here and elsewhere */
orderbysort->ssup_attno = 0;
/* No abbreviation */
orderbysort->abbreviate = false;
PrepareSortSupportFromOrderingOp(orderbyop, orderbysort);
PrepareSortSupportFromOrderingOp(orderbyop,
&indexstate->iss_SortSupport[i]);
get_typlenbyval(orderbyType,
&indexstate->iss_OrderByTypLens[i],
&indexstate->iss_OrderByTypByVals[i]);