From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
---|---|
To: | pgsql-committers(at)postgresql(dot)org |
Subject: | pgsql: Fix regexport.c to behave sanely with lookaround constraints. |
Date: | 2017-04-13 21:18:54 |
Message-ID: | E1cym8k-0007Df-Re@gemulon.postgresql.org |
Views: | Raw Message | Whole Thread | Download mbox | Resend email |
Thread: | |
Lists: | pgsql-committers |
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_4_STABLE
Details
-------
http://git.postgresql.org/pg/commitdiff/b179684c77bb16640cdea6fd3d7a1e333829334e
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(-)
From | Date | Subject | |
---|---|---|---|
Next Message | Peter Eisentraut | 2017-04-14 01:25:36 | pgsql: pg_dumpall: Allow --no-role-passwords and --binary-upgrade toget |
Previous Message | Bruce Momjian | 2017-04-13 17:51:04 | Re: pgsql: doc: add missing sect1 close tag |