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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

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]);