From bee7cd2a3664821e80ee0cc18d0b23bc7ea51bf5 Mon Sep 17 00:00:00 2001
From: Tom Lane <tgl@sss.pgh.pa.us>
Date: Tue, 7 Sep 1999 19:09:46 +0000
Subject: [PATCH] Repair logic error in LIKE: should not return LIKE_ABORT when
reach end of pattern before end of text. Improve code comments.
---
src/backend/utils/adt/like.c | 91 ++++++++++++++++++++----------------
1 file changed, 50 insertions(+), 41 deletions(-)
diff --git a/src/backend/utils/adt/like.c b/src/backend/utils/adt/like.c
index 73115522f2a..8c877c3ffdc 100644
--- a/src/backend/utils/adt/like.c
+++ b/src/backend/utils/adt/like.c
@@ -3,17 +3,14 @@
* like.c
* like expression handling code.
*
- * Copyright (c) 1994, Regents of the University of California
- *
- *
- * IDENTIFICATION
- * /usr/local/devel/pglite/cvs/src/backend/utils/adt/like.c,v 1.1 1995/07/30 23:55:36 emkxp01 Exp
- *
- *
* NOTES
* A big hack of the regexp.c code!! Contributed by
* Keith Parks <emkxp01@mtcc.demon.co.uk> (7/95).
*
+ * Copyright (c) 1994, Regents of the University of California
+ *
+ * IDENTIFICATION
+ * $Header: /cvsroot/pgsql/src/backend/utils/adt/like.c,v 1.31 1999/09/07 19:09:46 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -109,9 +106,7 @@ textnlike(struct varlena * s, struct varlena * p)
}
-/* $Revision: 1.30 $
-** "like.c" A first attempt at a LIKE operator for Postgres95.
-**
+/*
** Originally written by Rich $alz, mirror!rs, Wed Nov 26 19:03:17 EST 1986.
** Rich $alz is now <rsalz@bbn.com>.
** Special thanks to Lars Mathiesen <thorinn@diku.dk> for the LABORT code.
@@ -125,8 +120,7 @@ textnlike(struct varlena * s, struct varlena * p)
** All the nice shell RE matching stuff was replaced by just "_" and "%"
**
** As I don't have a copy of the SQL standard handy I wasn't sure whether
-** to leave in the '\' escape character handling. (I suspect the standard
-** handles "%%" as a single literal percent)
+** to leave in the '\' escape character handling.
**
** Keith Parks. <keith@mtcc.demon.co.uk>
**
@@ -140,15 +134,21 @@ textnlike(struct varlena * s, struct varlena * p)
#define LIKE_FALSE 0
#define LIKE_ABORT -1
-/*
-** Match text and p, return LIKE_TRUE, LIKE_FALSE, or LIKE_ABORT.
-*/
+/*--------------------
+ * Match text and p, return LIKE_TRUE, LIKE_FALSE, or LIKE_ABORT.
+ *
+ * LIKE_TRUE: they match
+ * LIKE_FALSE: they don't match
+ * LIKE_ABORT: not only don't they match, but the text is too short.
+ *
+ * If LIKE_ABORT is returned, then no suffix of the text can match the
+ * pattern either, so an upper-level % scan can stop scanning now.
+ *--------------------
+ */
static int
DoMatch(pg_wchar * text, pg_wchar * p)
{
- int matched;
-
- for (; *p && *text; text ++, p++)
+ for (; *p && *text; text++, p++)
{
switch (*p)
{
@@ -157,47 +157,55 @@ DoMatch(pg_wchar * text, pg_wchar * p)
p++;
/* FALLTHROUGH */
default:
- if (*text !=*p)
+ if (*text != *p)
return LIKE_FALSE;
break;
case '_':
- /* Match anything. */
+ /* Match any single character. */
break;
case '%':
/* %% is the same as % according to the SQL standard */
/* Advance past all %'s */
while (*p == '%')
p++;
+ /* Trailing percent matches everything. */
if (*p == '\0')
- /* Trailing percent matches everything. */
return LIKE_TRUE;
- while (*text)
+ /* Otherwise, scan for a text position at which we
+ * can match the rest of the pattern.
+ */
+ for (; *text; text++)
{
- /* Optimization to prevent most recursion */
- if ((*text == *p ||
- *p == '\\' || *p == '%' || *p == '_') &&
- (matched = DoMatch(text, p)) != LIKE_FALSE)
- return matched;
- text ++;
+ /* Optimization to prevent most recursion: don't recurse
+ * unless first pattern char might match this text char.
+ */
+ if (*text == *p || *p == '\\' || *p == '_')
+ {
+ int matched = DoMatch(text, p);
+ if (matched != LIKE_FALSE)
+ return matched; /* TRUE or ABORT */
+ }
}
+ /* End of text with no match, so no point in trying later
+ * places to start matching this pattern.
+ */
return LIKE_ABORT;
}
}
- if (*text !='\0')
- return LIKE_ABORT;
- else
- {
- /* End of input string. Do we have matching string remaining? */
- while (*p == '%') /* allow multiple %'s at end of pattern */
- p++;
- if (*p == '\0')
- return LIKE_TRUE;
- else
- return LIKE_ABORT;
- }
-}
+ if (*text != '\0')
+ return LIKE_FALSE; /* end of pattern, but not of text */
+ /* End of input string. Do we have matching pattern remaining? */
+ while (*p == '%') /* allow multiple %'s at end of pattern */
+ p++;
+ if (*p == '\0')
+ return LIKE_TRUE;
+ /* End of text with no match, so no point in trying later
+ * places to start matching this pattern.
+ */
+ return LIKE_ABORT;
+}
/*
** User-level routine. Returns TRUE or FALSE.
@@ -205,6 +213,7 @@ DoMatch(pg_wchar * text, pg_wchar * p)
static int
like(pg_wchar * text, pg_wchar * p)
{
+ /* Fast path for match-everything pattern */
if (p[0] == '%' && p[1] == '\0')
return TRUE;
return DoMatch(text, p) == LIKE_TRUE;
--
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