Thread: [COMMITTERS] pgsql: Fix regexport.c to behave sanely with lookaround constraints.
[COMMITTERS] pgsql: Fix regexport.c to behave sanely with lookaround constraints.
From
Tom Lane
Date:
Fix regexport.c to behave sanely with lookaround constraints. regexport.c thought it could just ignore LACON arcs, but the correct behavior is to treat them as satisfiable while consuming zero input (rather reminiscently of commit 9f1e642d5). Otherwise, the emitted simplified-NFA representation may contain no paths leading from initial to final state, which unsurprisingly confuses pg_trgm, as seen in bug #14623 from Jeff Janes. Since regexport's output representation has no concept of an arc that consumes zero input, recurse internally to find the next normal arc(s) after any LACON transitions. We'd be forced into changing that representation if a LACON could be the last arc reaching the final state, but fortunately the regex library never builds NFAs with such a configuration, so there always is a next normal arc. Back-patch to 9.3 where this logic was introduced. Discussion: https://postgr.es/m/20170413180503.25948.94871@wrigleys.postgresql.org Branch ------ REL9_6_STABLE Details ------- http://git.postgresql.org/pg/commitdiff/a70b18b89459c137d7c2554133981b0752450e4e Modified Files -------------- contrib/pg_trgm/expected/pg_trgm.out | 12 +++++ contrib/pg_trgm/sql/pg_trgm.sql | 3 ++ src/backend/regex/regexport.c | 92 ++++++++++++++++++++++++++---------- 3 files changed, 82 insertions(+), 25 deletions(-)