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Repair logic error in LIKE: should not return LIKE_ABORT

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when reach end of pattern before end of text.  Improve code comments.
This commit is contained in:
Tom Lane 1999-09-07 19:09:46 +00:00
parent ea582ad7e7
commit bee7cd2a36
1 changed files with 50 additions and 41 deletions
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91
src/backend/utils/adt/like.c
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@ -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;