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Fix corner-case failure in match_pattern_prefix().

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The planner's optimization code for LIKE and regex operators could
error out with a complaint like "no = operator for opfamily NNN"
if someone created a binary-compatible index (for example, a
bpchar_ops index on a text column) on the LIKE's left argument.

This is a consequence of careless refactoring in commit 74dfe58a5.
The old code in match_special_index_operator only accepted specific
combinations of the pattern operator and the index opclass, thereby
indirectly guaranteeing that the opclass would have a comparison
operator with the same LHS input type as the pattern operator.
While moving the logic out to a planner support function, I simplified
that test in a way that no longer guarantees that.  Really though we'd
like an altogether weaker dependency on the opclass, so rather than
put back exactly the old code, just allow lookup failure.  I have in
mind now to rewrite this logic completely, but this is the minimum
change needed to fix the bug in v12.

Per report from Manuel Rigger.  Back-patch to v12 where the mistake
came in.

Discussion: https://postgr.es/m/CA+u7OA7nnGYy8rY0vdTe811NuA+Frr9nbcBO9u2Z+JxqNaud+g@mail.gmail.com
This commit is contained in:
Tom Lane
2019-11-19 17:03:26 -05:00
parent b107140804
commit b3c265d7be
3 changed files with 95 additions and 4 deletions
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11
src/backend/utils/adt/like_support.c
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@ -265,7 +265,7 @@ match_pattern_prefix(Node *leftop,
* pattern-matching is not supported with nondeterministic collations. (We
* could also error out here, but by doing it later we get more precise
* error messages.) (It should be possible to support at least
* Pattern_Prefix_Exact, but no point as along as the actual
* Pattern_Prefix_Exact, but no point as long as the actual
* pattern-matching implementations don't support it.)
*
* expr_coll is not set for a non-collation-aware data type such as bytea.
@ -357,13 +357,16 @@ match_pattern_prefix(Node *leftop,
/*
* If we found an exact-match pattern, generate an "=" indexqual.
*
* (Despite the checks above, we might fail to find a suitable operator in
* some cases with binary-compatible opclasses. Just punt if so.)
*/
if (pstatus == Pattern_Prefix_Exact)
{
oproid = get_opfamily_member(opfamily, ldatatype, rdatatype,
BTEqualStrategyNumber);
if (oproid == InvalidOid)
elog(ERROR, "no = operator for opfamily %u", opfamily);
return NIL;
expr = make_opclause(oproid, BOOLOID, false,
(Expr *) leftop, (Expr *) prefix,
InvalidOid, indexcollation);
@ -379,7 +382,7 @@ match_pattern_prefix(Node *leftop,
oproid = get_opfamily_member(opfamily, ldatatype, rdatatype,
BTGreaterEqualStrategyNumber);
if (oproid == InvalidOid)
elog(ERROR, "no >= operator for opfamily %u", opfamily);
return NIL;
expr = make_opclause(oproid, BOOLOID, false,
(Expr *) leftop, (Expr *) prefix,
InvalidOid, indexcollation);
@ -396,7 +399,7 @@ match_pattern_prefix(Node *leftop,
oproid = get_opfamily_member(opfamily, ldatatype, rdatatype,
BTLessStrategyNumber);
if (oproid == InvalidOid)
elog(ERROR, "no < operator for opfamily %u", opfamily);
return result;
fmgr_info(get_opcode(oproid), &ltproc);
greaterstr = make_greater_string(prefix, &ltproc, indexcollation);
if (greaterstr)