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selfuncs.c: use pg_strxfrm() instead of strxfrm().

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pg_strxfrm() takes a pg_locale_t, so it works properly with all
providers. This improves estimates for ICU when performing linear
interpolation within a histogram bin.

Previously, convert_string_datum() always used strxfrm() and relied on
setlocale(). That did not produce good estimates for non-default or
non-libc collations.

Discussion: https://postgr.es/m/89475ee5487d795124f4e25118ea8f1853edb8cb.camel@j-davis.com
This commit is contained in:
Jeff Davis
2024-08-06 11:55:21 -07:00
parent a54d4ed183
commit a890ad2149
2 changed files with 25 additions and 11 deletions
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13
src/backend/utils/adt/selfuncs.c
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@@ -4639,7 +4639,7 @@ convert_one_string_to_scalar(char *value, int rangelo, int rangehi)
* On failure (e.g., unsupported typid), set *failure to true;
* otherwise, that variable is not changed. (We'll return NULL on failure.)
*
* When using a non-C locale, we must pass the string through strxfrm()
* When using a non-C locale, we must pass the string through pg_strxfrm()
* before continuing, so as to generate correct locale-specific results.
*/
static char *
@@ -4673,20 +4673,25 @@ convert_string_datum(Datum value, Oid typid, Oid collid, bool *failure)
if (!lc_collate_is_c(collid))
{
pg_locale_t mylocale = pg_newlocale_from_collation(collid);
char *xfrmstr;
size_t xfrmlen;
size_t xfrmlen2 PG_USED_FOR_ASSERTS_ONLY;
/*
* XXX: We could guess at a suitable output buffer size and only call
* strxfrm twice if our guess is too small.
* pg_strxfrm() twice if our guess is too small.
*
* XXX: strxfrm doesn't support UTF-8 encoding on Win32, it can return
* bogus data or set an error. This is not really a problem unless it
* crashes since it will only give an estimation error and nothing
* fatal.
*
* XXX: we do not check pg_strxfrm_enabled(). On some platforms and in
* some cases, libc strxfrm() may return the wrong results, but that
* will only lead to an estimation error.
*/
xfrmlen = strxfrm(NULL, val, 0);
xfrmlen = pg_strxfrm(NULL, val, 0, mylocale);
#ifdef WIN32
/*
@@ -4698,7 +4703,7 @@ convert_string_datum(Datum value, Oid typid, Oid collid, bool *failure)
return val;
#endif
xfrmstr = (char *) palloc(xfrmlen + 1);
xfrmlen2 = strxfrm(xfrmstr, val, xfrmlen + 1);
xfrmlen2 = pg_strxfrm(xfrmstr, val, xfrmlen + 1, mylocale);
/*
* Some systems (e.g., glibc) can return a smaller value from the