From 43e43771bc4b03a9e33be7261cc84dc7f65ae9ef Mon Sep 17 00:00:00 2001 From: Tom Lane Date: Mon, 28 Oct 2019 12:21:13 -0400 Subject: Handle empty-string edge cases correctly in strpos(). Commit 9556aa01c rearranged the innards of text_position() in a way that would make it not work for empty search strings. Which is fine, because all callers of that code special-case an empty pattern in some way. However, the primary use-case (text_position itself) got special-cased incorrectly: historically it's returned 1 not 0 for an empty search string. Restore the historical behavior. Per complaint from Austin Drenski (via Shay Rojansky). Back-patch to v12 where it got broken. Discussion: https://postgr.es/m/CADT4RqAz7oN4vkPir86Kg1_mQBmBxCp-L_=9vRpgSNPJf0KRkw@mail.gmail.com --- src/backend/utils/adt/varlena.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) (limited to 'src/backend/utils/adt/varlena.c') diff --git a/src/backend/utils/adt/varlena.c b/src/backend/utils/adt/varlena.c index 299d8b5790d..1587b4ed02a 100644 --- a/src/backend/utils/adt/varlena.c +++ b/src/backend/utils/adt/varlena.c @@ -1118,7 +1118,12 @@ text_position(text *t1, text *t2, Oid collid) TextPositionState state; int result; - if (VARSIZE_ANY_EXHDR(t1) < 1 || VARSIZE_ANY_EXHDR(t2) < 1) + /* Empty needle always matches at position 1 */ + if (VARSIZE_ANY_EXHDR(t2) < 1) + return 1; + + /* Otherwise, can't match if haystack is shorter than needle */ + if (VARSIZE_ANY_EXHDR(t1) < VARSIZE_ANY_EXHDR(t2)) return 0; text_position_setup(t1, t2, collid, &state); @@ -1272,6 +1277,9 @@ text_position_setup(text *t1, text *t2, Oid collid, TextPositionState *state) * Advance to the next match, starting from the end of the previous match * (or the beginning of the string, on first call). Returns true if a match * is found. + * + * Note that this refuses to match an empty-string needle. Most callers + * will have handled that case specially and we'll never see it here. */ static bool text_position_next(TextPositionState *state) -- cgit v1.2.3