Fix mishandling of leading '\' in nondeterministic LIKE. The loop in MatchText() processed a leading '\' without regard to nondeterministic locales, which is problematic if what the '\' precedes is an ordinary character that should be subject to nondeterministic matching. We'd insist on a literal match for it, which is not right and is not like what happens with a '\' that follows some ordinary characters. Worse, we'd then advance the text and pattern pointers by one byte, so that if the escaped character is multibyte the next loop iteration would take the nondeterministic code path starting at a point within the character. That could very possibly cause pg_strncoll() to misbehave.
The fix is quite simple: move the stanza that handles '\' down past the one that handles nondeterminism. The stanzas for '%' and '_' are fine where they are, but the '\' stanza is only correct for deterministic matching. The logic for nondeterministic cases is already prepared to do the right things with a '\'. While here, I replaced tests of "locale && !locale->deterministic" with a boolean local variable, reasoning that those are in the hot loop paths so saving a branch and indirect fetch is worth the trouble. I also improved a number of related comments. Author: Tom Lane <[email protected]> Discussion: https://postgr.es/m/[email protected] Backpatch-through: 18 Branch ------ REL_18_STABLE Details ------- https://git.postgresql.org/pg/commitdiff/51652c42da2e982fb7028970eea5eed4c670a555 Modified Files -------------- src/backend/utils/adt/like_match.c | 76 +++++++++++++++----------- src/test/regress/expected/collate.icu.utf8.out | 30 ++++++++++ src/test/regress/sql/collate.icu.utf8.sql | 6 ++ 3 files changed, 80 insertions(+), 32 deletions(-)
