From: Bruce Momjian <bruce@momjian.us>
Date: Wed, 25 May 2005 22:59:33 +0000 (+0000)
Subject: At the head of wchareq, length of (multibyte) character is compared by
X-Git-Url: http://git.postgresql.org/gitweb/static/gitweb.js?a=commitdiff_plain;h=2de3c98ad61112a97b07c6e9883d97efc2ecb2ec;p=users%2Fbernd%2Fpostgres.git

At the head of wchareq, length of (multibyte) character is compared by
using pg_mblen. Therefore, pg_mblen is executed many times, and it
becomes a bottleneck.

This patch makes a short cut, and reduces execution frequency of
pg_mblen by comparing the first byte first.

a_ogawa
---

diff --git a/src/backend/utils/adt/like.c b/src/backend/utils/adt/like.c
index eb6018498a..367dd69dea 100644
--- a/src/backend/utils/adt/like.c
+++ b/src/backend/utils/adt/like.c
@@ -50,12 +50,18 @@ static text *MB_do_like_escape(text *, text *);
 static int
 wchareq(unsigned char *p1, unsigned char *p2)
 {
-	int			l;
+	int			p1_len;
 
-	l = pg_mblen(p1);
-	if (pg_mblen(p2) != l)
+	/* Optimization:  quickly compare the first byte. */
+	if(*p1 != *p2)
 		return (0);
-	while (l--)
+
+	p1_len = pg_mblen(p1);
+	if (pg_mblen(p2) != p1_len)
+		return (0);
+
+	/* They are the same length */
+	while (p1_len--)
 	{
 		if (*p1++ != *p2++)
 			return (0);