From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
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To: | pgsql-committers(at)lists(dot)postgresql(dot)org |
Subject: | pgsql: Fix ts_headline() edge cases for empty query and empty search te |
Date: | 2023-04-06 19:52:55 |
Message-ID: | E1pkVfC-001jBy-2n@gemulon.postgresql.org |
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Lists: | pgsql-committers |
Fix ts_headline() edge cases for empty query and empty search text.
tsquery's GETQUERY() macro is only safe to apply to a tsquery
that is known non-empty; otherwise it gives a pointer to garbage.
Before commit 5a617d75d, ts_headline() avoided this pitfall, but
only in a very indirect, nonobvious way. (hlCover could not reach
its TS_execute call, because if the query contains no lexemes
then hlFirstIndex would surely return -1.) After that commit,
it fell into the trap, resulting in weird errors such as
"unrecognized operator" and/or valgrind complaints. In HEAD,
fix this by not calling TS_execute_locations() at all for an
empty query. In the back branches, add a defensive check to
hlCover() --- that's not fixing any live bug, but I judge the
code a bit too fragile as-is.
Also, both mark_hl_fragments() and mark_hl_words() were careless
about the possibility of empty search text: in the cases where
no match has been found, they'd end up telling mark_fragment() to
mark from word indexes 0 to 0 inclusive, even when there is no
word 0. This is harmless since we over-allocated the prs->words
array, but it does annoy valgrind. Fix so that the end index is -1
and thus mark_fragment() will do nothing in such cases.
Bottom line is that this fixes a live bug in HEAD, but in the
back branches it's only getting rid of a valgrind nitpick.
Back-patch anyway.
Per report from Alexander Lakhin.
Discussion: https://postgr.es/m/c27f642d-020b-01ff-ae61-086af287c4fd@gmail.com
Branch
------
master
Details
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https://git.postgresql.org/pg/commitdiff/029dea882a7aa34f46732473eed7c917505e6481
Modified Files
--------------
src/backend/tsearch/wparser_def.c | 21 ++++++++++++++-------
src/test/regress/expected/tsearch.out | 21 +++++++++++++++++++++
src/test/regress/sql/tsearch.sql | 6 ++++++
3 files changed, 41 insertions(+), 7 deletions(-)
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