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Reduce need for palloc/pfree overhead in varstr_cmp() by using fixed-size

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buffers on stack for short strings.
This commit is contained in:
Tom Lane 2002-11-17 23:01:30 +00:00
parent 35223af057
commit 8fbef3b55d
1 changed files with 25 additions and 14 deletions
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39
src/backend/utils/adt/varlena.c
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@ -8,7 +8,7 @@
* *
* *
* IDENTIFICATION * IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/utils/adt/varlena.c,v 1.92 2002/09/04 20:31:29 momjian Exp $ * $Header: /cvsroot/pgsql/src/backend/utils/adt/varlena.c,v 1.93 2002/11/17 23:01:30 tgl Exp $
* *
*------------------------------------------------------------------------- *-------------------------------------------------------------------------
*/ */
@ -736,36 +736,47 @@ int
varstr_cmp(char *arg1, int len1, char *arg2, int len2) varstr_cmp(char *arg1, int len1, char *arg2, int len2)
{ {
int result; int result;
char *a1p,
*a2p;
/* /*
* Unfortunately, there is no strncoll(), so in the non-C locale case * Unfortunately, there is no strncoll(), so in the non-C locale case
* we have to do some memory copying. This turns out to be * we have to do some memory copying. This turns out to be
* significantly slower, so we optimize the case where LC_COLLATE is * significantly slower, so we optimize the case where LC_COLLATE is
* C. * C. We also try to optimize relatively-short strings by avoiding
* palloc/pfree overhead.
*/ */
#define STACKBUFLEN 1024
if (!lc_collate_is_c()) if (!lc_collate_is_c())
{ {
a1p = (char *) palloc(len1 + 1); char a1buf[STACKBUFLEN];
a2p = (char *) palloc(len2 + 1); char a2buf[STACKBUFLEN];
char *a1p,
*a2p;
if (len1 >= STACKBUFLEN)
a1p = (char *) palloc(len1 + 1);
else
a1p = a1buf;
if (len2 >= STACKBUFLEN)
a2p = (char *) palloc(len2 + 1);
else
a2p = a2buf;
memcpy(a1p, arg1, len1); memcpy(a1p, arg1, len1);
*(a1p + len1) = '\0'; a1p[len1] = '\0';
memcpy(a2p, arg2, len2); memcpy(a2p, arg2, len2);
*(a2p + len2) = '\0'; a2p[len2] = '\0';
result = strcoll(a1p, a2p); result = strcoll(a1p, a2p);
pfree(a1p); if (len1 >= STACKBUFLEN)
pfree(a2p); pfree(a1p);
if (len2 >= STACKBUFLEN)
pfree(a2p);
} }
else else
{ {
a1p = arg1; result = strncmp(arg1, arg2, Min(len1, len2));
a2p = arg2;
result = strncmp(a1p, a2p, Min(len1, len2));
if ((result == 0) && (len1 != len2)) if ((result == 0) && (len1 != len2))
result = (len1 < len2) ? -1 : 1; result = (len1 < len2) ? -1 : 1;
} }