When the caller knows the smaller string length, memcmp and strncmp are
functionally equivalent. Since memcmp need not watch each byte for a NULL
terminator, it often compares a CPU word at a time for better performance. The
attached patch changes use of strncmp to memcmp where we have the length of the
shorter string. I was most interested in the varlena.c instances, but I tried
to find all applicable call sites. To benchmark it, I used the attached
"bench-texteq.sql". This patch improved my 5-run average timing of the SELECT
from 65.8s to 56.9s, a 13% improvement. I can't think of a case where the
change should be pessimal.
Thanks,
nm
*** a/contrib/hstore/hstore_io.c
--- b/contrib/hstore/hstore_io.c
***************
*** 280,288 **** comparePairs(const void *a, const void *b)
{
if (((Pairs *) a)->keylen == ((Pairs *) b)->keylen)
{
! int res = strncmp(((Pairs *) a)->key,
! ((Pairs *)
b)->key,
! ((Pairs *)
a)->keylen);
if (res)
return res;
--- 280,288 ----
{
if (((Pairs *) a)->keylen == ((Pairs *) b)->keylen)
{
! int res = memcmp(((Pairs *) a)->key,
! ((Pairs *)
b)->key,
! ((Pairs *)
a)->keylen);
if (res)
return res;
***************
*** 324,330 **** hstoreUniquePairs(Pairs *a, int4 l, int4 *buflen)
while (ptr - a < l)
{
if (ptr->keylen == res->keylen &&
! strncmp(ptr->key, res->key, res->keylen) == 0)
{
if (ptr->needfree)
{
--- 324,330 ----
while (ptr - a < l)
{
if (ptr->keylen == res->keylen &&
! memcmp(ptr->key, res->key, res->keylen) == 0)
{
if (ptr->needfree)
{
*** a/contrib/hstore/hstore_op.c
--- b/contrib/hstore/hstore_op.c
***************
*** 49,55 **** hstoreFindKey(HStore *hs, int *lowbound, char *key, int keylen)
stopMiddle = stopLow + (stopHigh - stopLow) / 2;
if (HS_KEYLEN(entries, stopMiddle) == keylen)
! difference = strncmp(HS_KEY(entries, base, stopMiddle),
key, keylen);
else
difference = (HS_KEYLEN(entries, stopMiddle) > keylen)
? 1 : -1;
--- 49,55 ----
stopMiddle = stopLow + (stopHigh - stopLow) / 2;
if (HS_KEYLEN(entries, stopMiddle) == keylen)
! difference = memcmp(HS_KEY(entries, base, stopMiddle),
key, keylen);
else
difference = (HS_KEYLEN(entries, stopMiddle) > keylen)
? 1 : -1;
***************
*** 263,269 **** hstore_delete(PG_FUNCTION_ARGS)
int len = HS_KEYLEN(es, i);
char *ptrs = HS_KEY(es, bufs, i);
! if (!(len == keylen && strncmp(ptrs, keyptr, keylen) == 0))
{
int vallen = HS_VALLEN(es, i);
--- 263,269 ----
int len = HS_KEYLEN(es, i);
char *ptrs = HS_KEY(es, bufs, i);
! if (!(len == keylen && memcmp(ptrs, keyptr, keylen) == 0))
{
int vallen = HS_VALLEN(es, i);
***************
*** 331,339 **** hstore_delete_array(PG_FUNCTION_ARGS)
int skeylen = HS_KEYLEN(es, i);
if (skeylen == key_pairs[j].keylen)
! difference = strncmp(HS_KEY(es, ps, i),
!
key_pairs[j].key,
!
key_pairs[j].keylen);
else
difference = (skeylen > key_pairs[j].keylen) ?
1 : -1;
}
--- 331,339 ----
int skeylen = HS_KEYLEN(es, i);
if (skeylen == key_pairs[j].keylen)
! difference = memcmp(HS_KEY(es, ps, i),
!
key_pairs[j].key,
!
key_pairs[j].keylen);
else
difference = (skeylen > key_pairs[j].keylen) ?
1 : -1;
}
***************
*** 416,424 **** hstore_delete_hstore(PG_FUNCTION_ARGS)
int s2keylen = HS_KEYLEN(es2, j);
if (skeylen == s2keylen)
! difference = strncmp(HS_KEY(es, ps, i),
!
HS_KEY(es2, ps2, j),
!
skeylen);
else
difference = (skeylen > s2keylen) ? 1 : -1;
}
--- 416,424 ----
int s2keylen = HS_KEYLEN(es2, j);
if (skeylen == s2keylen)
! difference = memcmp(HS_KEY(es, ps, i),
!
HS_KEY(es2, ps2, j),
!
skeylen);
else
difference = (skeylen > s2keylen) ? 1 : -1;
}
***************
*** 433,439 **** hstore_delete_hstore(PG_FUNCTION_ARGS)
if (snullval != HS_VALISNULL(es2, j)
|| (!snullval
&& (svallen != HS_VALLEN(es2, j)
! || strncmp(HS_VAL(es, ps, i),
HS_VAL(es2, ps2, j), svallen) != 0)))
{
HS_COPYITEM(ed, bufd, pd,
HS_KEY(es, ps, i),
HS_KEYLEN(es, i),
--- 433,439 ----
if (snullval != HS_VALISNULL(es2, j)
|| (!snullval
&& (svallen != HS_VALLEN(es2, j)
! || memcmp(HS_VAL(es, ps, i),
HS_VAL(es2, ps2, j), svallen) != 0)))
{
HS_COPYITEM(ed, bufd, pd,
HS_KEY(es, ps, i),
HS_KEYLEN(es, i),
***************
*** 526,534 **** hstore_concat(PG_FUNCTION_ARGS)
int s2keylen = HS_KEYLEN(es2,
s2idx);
if (s1keylen == s2keylen)
! difference = strncmp(HS_KEY(es1, ps1, s1idx),
!
HS_KEY(es2, ps2, s2idx),
!
s1keylen);
else
difference = (s1keylen > s2keylen) ? 1 : -1;
}
--- 526,534 ----
int s2keylen = HS_KEYLEN(es2,
s2idx);
if (s1keylen == s2keylen)
! difference = memcmp(HS_KEY(es1, ps1, s1idx),
!
HS_KEY(es2, ps2, s2idx),
!
s1keylen);
else
difference = (s1keylen > s2keylen) ? 1 : -1;
}
***************
*** 996,1002 **** hstore_contains(PG_FUNCTION_ARGS)
if (nullval != HS_VALISNULL(ve, idx)
|| (!nullval
&& (vallen != HS_VALLEN(ve, idx)
! || strncmp(HS_VAL(te, tstr, i), HS_VAL(ve, vstr, idx),
vallen))))
res = false;
}
else
--- 996,1002 ----
if (nullval != HS_VALISNULL(ve, idx)
|| (!nullval
&& (vallen != HS_VALLEN(ve, idx)
! || memcmp(HS_VAL(te, tstr, i), HS_VAL(ve, vstr, idx),
vallen))))
res = false;
}
else
*** a/contrib/ltree/lquery_op.c
--- b/contrib/ltree/lquery_op.c
***************
*** 111,117 **** checkLevel(lquery_level *curq, ltree_level *curt)
for (i = 0; i < curq->numvar; i++)
{
! cmpptr = (curvar->flag & LVAR_INCASE) ? ltree_strncasecmp :
strncmp;
if (curvar->flag & LVAR_SUBLEXEME)
{
--- 111,117 ----
for (i = 0; i < curq->numvar; i++)
{
! cmpptr = (curvar->flag & LVAR_INCASE) ? ltree_strncasecmp :
memcmp;
if (curvar->flag & LVAR_SUBLEXEME)
{
*** a/contrib/ltree/ltree_gist.c
--- b/contrib/ltree/ltree_gist.c
***************
*** 546,552 **** gist_tqcmp(ltree *t, lquery *q)
while (an > 0 && bn > 0)
{
bl = LQL_FIRST(ql);
! if ((res = strncmp(al->name, bl->name, Min(al->len, bl->len)))
== 0)
{
if (al->len != bl->len)
return al->len - bl->len;
--- 546,552 ----
while (an > 0 && bn > 0)
{
bl = LQL_FIRST(ql);
! if ((res = memcmp(al->name, bl->name, Min(al->len, bl->len)))
== 0)
{
if (al->len != bl->len)
return al->len - bl->len;
*** a/contrib/ltree/ltree_op.c
--- b/contrib/ltree/ltree_op.c
***************
*** 68,74 **** ltree_compare(const ltree *a, const ltree *b)
while (an > 0 && bn > 0)
{
! if ((res = strncmp(al->name, bl->name, Min(al->len, bl->len)))
== 0)
{
if (al->len != bl->len)
return (al->len - bl->len) * 10 * (an + 1);
--- 68,74 ----
while (an > 0 && bn > 0)
{
! if ((res = memcmp(al->name, bl->name, Min(al->len, bl->len)))
== 0)
{
if (al->len != bl->len)
return (al->len - bl->len) * 10 * (an + 1);
***************
*** 165,171 **** inner_isparent(const ltree *c, const ltree *p)
{
if (cl->len != pl->len)
return false;
! if (strncmp(cl->name, pl->name, cl->len))
return false;
pn--;
--- 165,171 ----
{
if (cl->len != pl->len)
return false;
! if (memcmp(cl->name, pl->name, cl->len))
return false;
pn--;
***************
*** 373,379 **** ltree_index(PG_FUNCTION_ARGS)
bptr = LTREE_FIRST(b);
for (j = 0; j < b->numlevel; j++)
{
! if (!(aptr->len == bptr->len &&
strncmp(aptr->name, bptr->name, aptr->len) == 0))
break;
aptr = LEVEL_NEXT(aptr);
bptr = LEVEL_NEXT(bptr);
--- 373,379 ----
bptr = LTREE_FIRST(b);
for (j = 0; j < b->numlevel; j++)
{
! if (!(aptr->len == bptr->len &&
memcmp(aptr->name, bptr->name, aptr->len) == 0))
break;
aptr = LEVEL_NEXT(aptr);
bptr = LEVEL_NEXT(bptr);
***************
*** 451,457 **** lca_inner(ltree **a, int len)
num = 0;
for (i = 0; i < Min(tmp, (*ptr)->numlevel - 1); i++)
{
! if (l1->len == l2->len && strncmp(l1->name,
l2->name, l1->len) == 0)
num = i + 1;
else
break;
--- 451,457 ----
num = 0;
for (i = 0; i < Min(tmp, (*ptr)->numlevel - 1); i++)
{
! if (l1->len == l2->len && memcmp(l1->name,
l2->name, l1->len) == 0)
num = i + 1;
else
break;
*** a/contrib/ltree/ltxtquery_op.c
--- b/contrib/ltree/ltxtquery_op.c
***************
*** 57,63 **** checkcondition_str(void *checkval, ITEM *val)
char *op = ((CHKVAL *) checkval)->operand + val->distance;
int (*cmpptr) (const char *, const char *, size_t);
! cmpptr = (val->flag & LVAR_INCASE) ? ltree_strncasecmp : strncmp;
while (tlen > 0)
{
if (val->flag & LVAR_SUBLEXEME)
--- 57,63 ----
char *op = ((CHKVAL *) checkval)->operand + val->distance;
int (*cmpptr) (const char *, const char *, size_t);
! cmpptr = (val->flag & LVAR_INCASE) ? ltree_strncasecmp : memcmp;
while (tlen > 0)
{
if (val->flag & LVAR_SUBLEXEME)
*** a/src/backend/nodes/readfuncs.c
--- b/src/backend/nodes/readfuncs.c
***************
*** 1196,1202 **** parseNodeString(void)
token = pg_strtok(&length);
#define MATCH(tokname, namelen) \
! (length == namelen && strncmp(token, tokname, namelen) == 0)
if (MATCH("QUERY", 5))
return_value = _readQuery();
--- 1196,1202 ----
token = pg_strtok(&length);
#define MATCH(tokname, namelen) \
! (length == namelen && memcmp(token, tokname, namelen) == 0)
if (MATCH("QUERY", 5))
return_value = _readQuery();
*** a/src/backend/tsearch/spell.c
--- b/src/backend/tsearch/spell.c
***************
*** 1502,1508 **** CheckCompoundAffixes(CMPDAffix **ptr, char *word, int len,
bool CheckInPlace)
{
while ((*ptr)->affix)
{
! if (len > (*ptr)->len && strncmp((*ptr)->affix, word,
(*ptr)->len) == 0)
{
len = (*ptr)->len;
issuffix = (*ptr)->issuffix;
--- 1502,1508 ----
{
while ((*ptr)->affix)
{
! if (len > (*ptr)->len && memcmp((*ptr)->affix, word,
(*ptr)->len) == 0)
{
len = (*ptr)->len;
issuffix = (*ptr)->issuffix;
*** a/src/backend/tsearch/to_tsany.c
--- b/src/backend/tsearch/to_tsany.c
***************
*** 90,96 **** uniqueWORD(ParsedWord *a, int4 l)
while (ptr - a < l)
{
if (!(ptr->len == res->len &&
! strncmp(ptr->word, res->word, res->len) == 0))
{
/*
* Got a new word, so put it in result
--- 90,96 ----
while (ptr - a < l)
{
if (!(ptr->len == res->len &&
! memcmp(ptr->word, res->word, res->len) == 0))
{
/*
* Got a new word, so put it in result
*** a/src/backend/tsearch/ts_selfuncs.c
--- b/src/backend/tsearch/ts_selfuncs.c
***************
*** 316,323 **** tsquery_opr_selec(QueryItem *item, char *operand,
int tlen =
VARSIZE_ANY_EXHDR(t->element);
if (tlen >= key.length &&
! strncmp(key.lexeme,
VARDATA_ANY(t->element),
! key.length) == 0)
matched += t->frequency;
allmcvs += t->frequency;
}
--- 316,323 ----
int tlen =
VARSIZE_ANY_EXHDR(t->element);
if (tlen >= key.length &&
! memcmp(key.lexeme,
VARDATA_ANY(t->element),
! key.length) == 0)
matched += t->frequency;
allmcvs += t->frequency;
}
***************
*** 430,434 **** compare_lexeme_textfreq(const void *e1, const void *e2)
return -1;
/* Fall back on byte-for-byte comparison */
! return strncmp(key->lexeme, VARDATA_ANY(t->element), len1);
}
--- 430,434 ----
return -1;
/* Fall back on byte-for-byte comparison */
! return memcmp(key->lexeme, VARDATA_ANY(t->element), len1);
}
*** a/src/backend/tsearch/ts_typanalyze.c
--- b/src/backend/tsearch/ts_typanalyze.c
***************
*** 488,494 **** lexeme_compare(const void *key1, const void *key2)
else if (d1->length < d2->length)
return -1;
/* Lengths are equal, do a byte-by-byte comparison */
! return strncmp(d1->lexeme, d2->lexeme, d1->length);
}
/*
--- 488,494 ----
else if (d1->length < d2->length)
return -1;
/* Lengths are equal, do a byte-by-byte comparison */
! return memcmp(d1->lexeme, d2->lexeme, d1->length);
}
/*
*** a/src/backend/utils/adt/varchar.c
--- b/src/backend/utils/adt/varchar.c
***************
*** 690,696 **** bpchareq(PG_FUNCTION_ARGS)
if (len1 != len2)
result = false;
else
! result = (strncmp(VARDATA_ANY(arg1), VARDATA_ANY(arg2), len1)
== 0);
PG_FREE_IF_COPY(arg1, 0);
PG_FREE_IF_COPY(arg2, 1);
--- 690,696 ----
if (len1 != len2)
result = false;
else
! result = (memcmp(VARDATA_ANY(arg1), VARDATA_ANY(arg2), len1) ==
0);
PG_FREE_IF_COPY(arg1, 0);
PG_FREE_IF_COPY(arg2, 1);
***************
*** 717,723 **** bpcharne(PG_FUNCTION_ARGS)
if (len1 != len2)
result = true;
else
! result = (strncmp(VARDATA_ANY(arg1), VARDATA_ANY(arg2), len1)
!= 0);
PG_FREE_IF_COPY(arg1, 0);
PG_FREE_IF_COPY(arg2, 1);
--- 717,723 ----
if (len1 != len2)
result = true;
else
! result = (memcmp(VARDATA_ANY(arg1), VARDATA_ANY(arg2), len1) !=
0);
PG_FREE_IF_COPY(arg1, 0);
PG_FREE_IF_COPY(arg2, 1);
***************
*** 905,911 **** internal_bpchar_pattern_compare(BpChar *arg1, BpChar *arg2)
len1 = bcTruelen(arg1);
len2 = bcTruelen(arg2);
! result = strncmp(VARDATA_ANY(arg1), VARDATA_ANY(arg2), Min(len1, len2));
if (result != 0)
return result;
else if (len1 < len2)
--- 905,911 ----
len1 = bcTruelen(arg1);
len2 = bcTruelen(arg2);
! result = memcmp(VARDATA_ANY(arg1), VARDATA_ANY(arg2), Min(len1, len2));
if (result != 0)
return result;
else if (len1 < len2)
*** a/src/backend/utils/adt/varlena.c
--- b/src/backend/utils/adt/varlena.c
***************
*** 1286,1292 **** varstr_cmp(char *arg1, int len1, char *arg2, int len2)
*/
if (lc_collate_is_c())
{
! result = strncmp(arg1, arg2, Min(len1, len2));
if ((result == 0) && (len1 != len2))
result = (len1 < len2) ? -1 : 1;
}
--- 1286,1292 ----
*/
if (lc_collate_is_c())
{
! result = memcmp(arg1, arg2, Min(len1, len2));
if ((result == 0) && (len1 != len2))
result = (len1 < len2) ? -1 : 1;
}
***************
*** 1370,1376 **** varstr_cmp(char *arg1, int len1, char *arg2, int len2)
*/
if (result == 0)
{
! result = strncmp(arg1, arg2, Min(len1, len2));
if ((result == 0) && (len1 != len2))
result = (len1 < len2) ? -1 : 1;
}
--- 1370,1376 ----
*/
if (result == 0)
{
! result = memcmp(arg1, arg2, Min(len1, len2));
if ((result == 0) && (len1 != len2))
result = (len1 < len2) ? -1 : 1;
}
***************
*** 1462,1469 **** texteq(PG_FUNCTION_ARGS)
if (VARSIZE_ANY_EXHDR(arg1) != VARSIZE_ANY_EXHDR(arg2))
result = false;
else
! result = (strncmp(VARDATA_ANY(arg1), VARDATA_ANY(arg2),
! VARSIZE_ANY_EXHDR(arg1)) ==
0);
PG_FREE_IF_COPY(arg1, 0);
PG_FREE_IF_COPY(arg2, 1);
--- 1462,1469 ----
if (VARSIZE_ANY_EXHDR(arg1) != VARSIZE_ANY_EXHDR(arg2))
result = false;
else
! result = (memcmp(VARDATA_ANY(arg1), VARDATA_ANY(arg2),
! VARSIZE_ANY_EXHDR(arg1)) == 0);
PG_FREE_IF_COPY(arg1, 0);
PG_FREE_IF_COPY(arg2, 1);
***************
*** 1485,1492 **** textne(PG_FUNCTION_ARGS)
if (VARSIZE_ANY_EXHDR(arg1) != VARSIZE_ANY_EXHDR(arg2))
result = true;
else
! result = (strncmp(VARDATA_ANY(arg1), VARDATA_ANY(arg2),
! VARSIZE_ANY_EXHDR(arg1)) !=
0);
PG_FREE_IF_COPY(arg1, 0);
PG_FREE_IF_COPY(arg2, 1);
--- 1485,1492 ----
if (VARSIZE_ANY_EXHDR(arg1) != VARSIZE_ANY_EXHDR(arg2))
result = true;
else
! result = (memcmp(VARDATA_ANY(arg1), VARDATA_ANY(arg2),
! VARSIZE_ANY_EXHDR(arg1)) != 0);
PG_FREE_IF_COPY(arg1, 0);
PG_FREE_IF_COPY(arg2, 1);
***************
*** 1612,1618 **** internal_text_pattern_compare(text *arg1, text *arg2)
len1 = VARSIZE_ANY_EXHDR(arg1);
len2 = VARSIZE_ANY_EXHDR(arg2);
! result = strncmp(VARDATA_ANY(arg1), VARDATA_ANY(arg2), Min(len1, len2));
if (result != 0)
return result;
else if (len1 < len2)
--- 1612,1618 ----
len1 = VARSIZE_ANY_EXHDR(arg1);
len2 = VARSIZE_ANY_EXHDR(arg2);
! result = memcmp(VARDATA_ANY(arg1), VARDATA_ANY(arg2), Min(len1, len2));
if (result != 0)
return result;
else if (len1 < len2)
\timing on
-- Benchmark "texteq". Creates a table having a single "text" column and
-- inserts a small number of rows, each having the same length (~10 MiB; the
-- data does compress over 98%). The datums differ only in the last few
-- characters. Then, compare to another, similar string.
BEGIN;
CREATE TEMP TABLE t (c text);
INSERT INTO t
SELECT repeat('foobarbazz', 1024 * 1024) || to_char(n, '000000')
FROM generate_series(1,100) ser(n);
SELECT pg_size_pretty(pg_total_relation_size('t'));
CREATE FUNCTION pg_temp.try() RETURNS void LANGUAGE plpgsql AS $$
BEGIN
FOR i IN 1..15 LOOP
PERFORM count(*) FROM t WHERE c = repeat('foobarbazz', 1024 *
1024) || to_char(0, '000000');
END LOOP;
END
$$;
SELECT pg_temp.try();
SELECT pg_temp.try();
SELECT pg_temp.try();
SELECT pg_temp.try();
SELECT pg_temp.try();
ROLLBACK;
--
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