On 28/10/2019 17:57, Tom Lane wrote:
Robert Haas <robertmh...@gmail.com> writes:
On Mon, Oct 28, 2019 at 11:02 AM Shay Rojansky <r...@roji.org> wrote:
Before PG12, select strpos('test', '') returns 1 (empty substring found at
first position of the string), whereas starting with PG12 it returns 0 (empty
substring not found).
It looks to me like this got broken here:
commit 9556aa01c69a26ca726d8dda8e395acc7c1e30fc
Author: Heikki Linnakangas <heikki.linnakan...@iki.fi>
Date: Fri Jan 25 16:25:05 2019 +0200
Use single-byte Boyer-Moore-Horspool search even with multibyte encodings.
Not sure what happened exactly.
I think the problem is lack of clarity about the edge cases.
The patch added this short-circuit right at the top of text_position():
+ if (VARSIZE_ANY_EXHDR(t1) < 1 || VARSIZE_ANY_EXHDR(t2) < 1)
+ return 0;
and as this example shows, that's the Wrong Thing. Fortunately,
it also seems easily fixed.
Tom fixed this in commit bd1ef5799b; thanks!
To be sure, I also checked the SQL standard for what POSITION('' IN
'test') is supposed to return. It agrees that 1 is correct:
> If CHAR_LENGTH(CVE1) is 0 (zero), then the result is 1 (one).
- Heikki
