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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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81
src/backend/utils/adt/like.c
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@ -3,17 +3,14 @@
* like.c * like.c
* like expression handling code. * 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 * NOTES
* A big hack of the regexp.c code!! Contributed by * A big hack of the regexp.c code!! Contributed by
* Keith Parks <emkxp01@mtcc.demon.co.uk> (7/95). * 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. ** Originally written by Rich $alz, mirror!rs, Wed Nov 26 19:03:17 EST 1986.
** Rich $alz is now <rsalz@bbn.com>. ** Rich $alz is now <rsalz@bbn.com>.
** Special thanks to Lars Mathiesen <thorinn@diku.dk> for the LABORT code. ** 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 "%" ** 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 ** 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 ** to leave in the '\' escape character handling.
** handles "%%" as a single literal percent)
** **
** Keith Parks. <keith@mtcc.demon.co.uk> ** Keith Parks. <keith@mtcc.demon.co.uk>
** **
@ -140,15 +134,21 @@ textnlike(struct varlena * s, struct varlena * p)
#define LIKE_FALSE 0 #define LIKE_FALSE 0
#define LIKE_ABORT -1 #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 static int
DoMatch(pg_wchar * text, pg_wchar * p) DoMatch(pg_wchar * text, pg_wchar * p)
{ {
int matched; for (; *p && *text; text++, p++)
for (; *p && *text; text ++, p++)
{ {
switch (*p) switch (*p)
{ {
@ -157,54 +157,63 @@ DoMatch(pg_wchar * text, pg_wchar * p)
p++; p++;
/* FALLTHROUGH */ /* FALLTHROUGH */
default: default:
if (*text !=*p) if (*text != *p)
return LIKE_FALSE; return LIKE_FALSE;
break; break;
case '_': case '_':
/* Match anything. */ /* Match any single character. */
break; break;
case '%': case '%':
/* %% is the same as % according to the SQL standard */ /* %% is the same as % according to the SQL standard */
/* Advance past all %'s */ /* Advance past all %'s */
while (*p == '%') while (*p == '%')
p++; p++;
if (*p == '\0')
/* Trailing percent matches everything. */ /* Trailing percent matches everything. */
if (*p == '\0')
return LIKE_TRUE; 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 */ /* Optimization to prevent most recursion: don't recurse
if ((*text == *p || * unless first pattern char might match this text char.
*p == '\\' || *p == '%' || *p == '_') && */
(matched = DoMatch(text, p)) != LIKE_FALSE) if (*text == *p || *p == '\\' || *p == '_')
return matched; {
text ++; 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; return LIKE_ABORT;
} }
} }
if (*text !='\0') if (*text != '\0')
return LIKE_ABORT; return LIKE_FALSE; /* end of pattern, but not of text */
else
{ /* End of input string. Do we have matching pattern remaining? */
/* End of input string. Do we have matching string remaining? */
while (*p == '%') /* allow multiple %'s at end of pattern */ while (*p == '%') /* allow multiple %'s at end of pattern */
p++; p++;
if (*p == '\0') if (*p == '\0')
return LIKE_TRUE; return LIKE_TRUE;
else /* End of text with no match, so no point in trying later
* places to start matching this pattern.
*/
return LIKE_ABORT; return LIKE_ABORT;
}
} }
/* /*
** User-level routine. Returns TRUE or FALSE. ** User-level routine. Returns TRUE or FALSE.
*/ */
static int static int
like(pg_wchar * text, pg_wchar * p) like(pg_wchar * text, pg_wchar * p)
{ {
/* Fast path for match-everything pattern */
if (p[0] == '%' && p[1] == '\0') if (p[0] == '%' && p[1] == '\0')
return TRUE; return TRUE;
return DoMatch(text, p) == LIKE_TRUE; return DoMatch(text, p) == LIKE_TRUE;