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Commitbee7cd2

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Repair logic error in LIKE: should not return LIKE_ABORT
when reach end of pattern before end of text. Improve code comments.
1 parentea582ad commitbee7cd2

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1 file changed

+50
-41
lines changed

1 file changed

+50
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lines changed

‎src/backend/utils/adt/like.c

Lines changed: 50 additions & 41 deletions
Original file line numberDiff line numberDiff line change
@@ -3,17 +3,14 @@
33
* like.c
44
* like expression handling code.
55
*
6-
* Copyright (c) 1994, Regents of the University of California
7-
*
8-
*
9-
* IDENTIFICATION
10-
* /usr/local/devel/pglite/cvs/src/backend/utils/adt/like.c,v 1.1 1995/07/30 23:55:36 emkxp01 Exp
11-
*
12-
*
136
* NOTES
147
*A big hack of the regexp.c code!! Contributed by
158
*Keith Parks <emkxp01@mtcc.demon.co.uk> (7/95).
169
*
10+
* Copyright (c) 1994, Regents of the University of California
11+
*
12+
* IDENTIFICATION
13+
*$Header: /cvsroot/pgsql/src/backend/utils/adt/like.c,v 1.31 1999/09/07 19:09:46 tgl Exp $
1714
*
1815
*-------------------------------------------------------------------------
1916
*/
@@ -109,9 +106,7 @@ textnlike(struct varlena * s, struct varlena * p)
109106
}
110107

111108

112-
/*$Revision: 1.30 $
113-
**"like.c" A first attempt at a LIKE operator for Postgres95.
114-
**
109+
/*
115110
**Originally written by Rich $alz, mirror!rs, Wed Nov 26 19:03:17 EST 1986.
116111
**Rich $alz is now <rsalz@bbn.com>.
117112
**Special thanks to Lars Mathiesen <thorinn@diku.dk> for the LABORT code.
@@ -125,8 +120,7 @@ textnlike(struct varlena * s, struct varlena * p)
125120
**All the nice shell RE matching stuff was replaced by just "_" and "%"
126121
**
127122
**As I don't have a copy of the SQL standard handy I wasn't sure whether
128-
**to leave in the '\' escape character handling. (I suspect the standard
129-
**handles "%%" as a single literal percent)
123+
**to leave in the '\' escape character handling.
130124
**
131125
**Keith Parks. <keith@mtcc.demon.co.uk>
132126
**
@@ -140,15 +134,21 @@ textnlike(struct varlena * s, struct varlena * p)
140134
#defineLIKE_FALSE0
141135
#defineLIKE_ABORT-1
142136

143-
/*
144-
**Match text and p, return LIKE_TRUE, LIKE_FALSE, or LIKE_ABORT.
145-
*/
137+
/*--------------------
138+
*Match text and p, return LIKE_TRUE, LIKE_FALSE, or LIKE_ABORT.
139+
*
140+
*LIKE_TRUE: they match
141+
*LIKE_FALSE: they don't match
142+
*LIKE_ABORT: not only don't they match, but the text is too short.
143+
*
144+
* If LIKE_ABORT is returned, then no suffix of the text can match the
145+
* pattern either, so an upper-level % scan can stop scanning now.
146+
*--------------------
147+
*/
146148
staticint
147149
DoMatch(pg_wchar*text,pg_wchar*p)
148150
{
149-
intmatched;
150-
151-
for (;*p&&*text;text++,p++)
151+
for (;*p&&*text;text++,p++)
152152
{
153153
switch (*p)
154154
{
@@ -157,54 +157,63 @@ DoMatch(pg_wchar * text, pg_wchar * p)
157157
p++;
158158
/* FALLTHROUGH */
159159
default:
160-
if (*text!=*p)
160+
if (*text!=*p)
161161
returnLIKE_FALSE;
162162
break;
163163
case'_':
164-
/* Matchanything. */
164+
/* Matchany single character. */
165165
break;
166166
case'%':
167167
/* %% is the same as % according to the SQL standard */
168168
/* Advance past all %'s */
169169
while (*p=='%')
170170
p++;
171+
/* Trailing percent matches everything. */
171172
if (*p=='\0')
172-
/* Trailing percent matches everything. */
173173
returnLIKE_TRUE;
174-
while (*text)
174+
/* Otherwise, scan for a text position at which we
175+
* can match the rest of the pattern.
176+
*/
177+
for (;*text;text++)
175178
{
176-
/* Optimization to prevent most recursion */
177-
if ((*text==*p||
178-
*p=='\\'||*p=='%'||*p=='_')&&
179-
(matched=DoMatch(text,p))!=LIKE_FALSE)
180-
returnmatched;
181-
text++;
179+
/* Optimization to prevent most recursion: don't recurse
180+
* unless first pattern char might match this text char.
181+
*/
182+
if (*text==*p||*p=='\\'||*p=='_')
183+
{
184+
intmatched=DoMatch(text,p);
185+
if (matched!=LIKE_FALSE)
186+
returnmatched;/* TRUE or ABORT */
187+
}
182188
}
189+
/* End of text with no match, so no point in trying later
190+
* places to start matching this pattern.
191+
*/
183192
returnLIKE_ABORT;
184193
}
185194
}
186195

187-
if (*text!='\0')
188-
returnLIKE_ABORT;
189-
else
190-
{
191-
/* End of input string. Do we have matching string remaining? */
192-
while (*p=='%')/* allow multiple %'s at end of pattern */
193-
p++;
194-
if (*p=='\0')
195-
returnLIKE_TRUE;
196-
else
197-
returnLIKE_ABORT;
198-
}
199-
}
196+
if (*text!='\0')
197+
returnLIKE_FALSE;/* end of pattern, but not of text */
200198

199+
/* End of input string. Do we have matching pattern remaining? */
200+
while (*p=='%')/* allow multiple %'s at end of pattern */
201+
p++;
202+
if (*p=='\0')
203+
returnLIKE_TRUE;
204+
/* End of text with no match, so no point in trying later
205+
* places to start matching this pattern.
206+
*/
207+
returnLIKE_ABORT;
208+
}
201209

202210
/*
203211
**User-level routine. Returns TRUE or FALSE.
204212
*/
205213
staticint
206214
like(pg_wchar*text,pg_wchar*p)
207215
{
216+
/* Fast path for match-everything pattern */
208217
if (p[0]=='%'&&p[1]=='\0')
209218
return TRUE;
210219
returnDoMatch(text,p)==LIKE_TRUE;

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