Branch data Line data Source code
1 : : /*-------------------------------------------------------------------------
2 : : *
3 : : * like_match.c
4 : : * LIKE pattern matching internal code.
5 : : *
6 : : * This file is included by like.c four times, to provide matching code for
7 : : * (1) single-byte encodings, (2) UTF8, (3) other multi-byte encodings,
8 : : * and (4) case insensitive matches in single-byte encodings.
9 : : * (UTF8 is a special case because we can use a much more efficient version
10 : : * of NextChar than can be used for general multi-byte encodings.)
11 : : *
12 : : * Before the inclusion, we need to define the following macros:
13 : : *
14 : : * NextChar
15 : : * MatchText - to name of function wanted
16 : : * do_like_escape - name of function if wanted - needs CHAREQ and CopyAdvChar
17 : : * MATCH_LOWER - define for case (4) to specify case folding for 1-byte chars
18 : : *
19 : : * Copyright (c) 1996-2026, PostgreSQL Global Development Group
20 : : *
21 : : * IDENTIFICATION
22 : : * src/backend/utils/adt/like_match.c
23 : : *
24 : : *-------------------------------------------------------------------------
25 : : */
26 : :
27 : : /*
28 : : * Originally written by Rich $alz, mirror!rs, Wed Nov 26 19:03:17 EST 1986.
29 : : * Rich $alz is now <rsalz@bbn.com>.
30 : : * Special thanks to Lars Mathiesen <thorinn@diku.dk> for the
31 : : * LIKE_ABORT code.
32 : : *
33 : : * This code was shamelessly stolen from the "pql" code by myself and
34 : : * slightly modified :)
35 : : *
36 : : * All references to the word "star" were replaced by "percent"
37 : : * All references to the word "wild" were replaced by "like"
38 : : *
39 : : * All the nice shell RE matching stuff was replaced by just "_" and "%"
40 : : *
41 : : * As I don't have a copy of the SQL standard handy I wasn't sure whether
42 : : * to leave in the '\' escape character handling.
43 : : *
44 : : * Keith Parks. <keith@mtcc.demon.co.uk>
45 : : *
46 : : * SQL lets you specify the escape character by saying
47 : : * LIKE <pattern> ESCAPE <escape character>. We are a small operation
48 : : * so we force you to use '\'. - ay 7/95
49 : : *
50 : : * Now we have the like_escape() function that converts patterns with
51 : : * any specified escape character (or none at all) to the internal
52 : : * default escape character, which is still '\'. - tgl 9/2000
53 : : *
54 : : * The code is rewritten to avoid requiring null-terminated strings,
55 : : * which in turn allows us to leave out some memcpy() operations.
56 : : * This code should be faster and take less memory, but no promises...
57 : : * - thomas 2000-08-06
58 : : */
59 : :
60 : :
61 : : /*--------------------
62 : : * Match text and pattern, return LIKE_TRUE, LIKE_FALSE, or LIKE_ABORT.
63 : : *
64 : : * LIKE_TRUE: they match
65 : : * LIKE_FALSE: they don't match
66 : : * LIKE_ABORT: not only don't they match, but the text is too short.
67 : : *
68 : : * If LIKE_ABORT is returned, then no suffix of the text can match the
69 : : * pattern either, so an upper-level % scan can stop scanning now.
70 : : *--------------------
71 : : */
72 : :
73 : : /*
74 : : * MATCH_LOWER is defined for ILIKE in the C locale as an optimization. Other
75 : : * locales must casefold the inputs before matching.
76 : : */
77 : : #ifdef MATCH_LOWER
78 : : #define GETCHAR(t) pg_ascii_tolower(t)
79 : : #else
80 : : #define GETCHAR(t) (t)
81 : : #endif
82 : :
83 : : static int
84 : 1221427 : MatchText(const char *t, int tlen, const char *p, int plen, pg_locale_t locale)
85 : : {
86 : : /* Fast path for match-everything pattern */
87 [ - + # # : 1221427 : if (plen == 1 && *p == '%')
+ + + + #
# # # - +
# # ]
88 : 7 : return LIKE_TRUE;
89 : :
90 : : /* Since this function recurses, it could be driven to stack overflow */
91 : 1221420 : check_stack_depth();
92 : :
93 : : /*
94 : : * In this loop, we advance by char when matching wildcards (and thus on
95 : : * recursive entry to this function we are properly char-synced). On other
96 : : * occasions it is safe to advance by byte, as the text and pattern will
97 : : * be in lockstep. This allows us to perform all comparisons between the
98 : : * text and pattern on a byte by byte basis, even for multi-byte
99 : : * encodings.
100 : : */
101 [ + + + + : 3203450 : while (tlen > 0 && plen > 0)
+ + + + #
# # # + +
+ + ]
102 : : {
103 [ + + + + : 3201873 : if (*p == '\\')
# # - + ]
104 : : {
105 : : /* Next pattern byte must match literally, whatever it is */
106 : 2150 : NextByte(p, plen);
107 : : /* ... and there had better be one, per SQL standard */
108 [ + - + - : 2150 : if (plen <= 0)
# # # # ]
109 [ # # # # : 0 : ereport(ERROR,
# # # # #
# # # # #
# # ]
110 : : (errcode(ERRCODE_INVALID_ESCAPE_SEQUENCE),
111 : : errmsg("LIKE pattern must not end with escape character")));
112 [ - + + + : 2150 : if (GETCHAR(*p) != GETCHAR(*t))
# # # # ]
113 : 572 : return LIKE_FALSE;
114 : 1578 : }
115 [ + - + + : 3199723 : else if (*p == '%')
# # + - ]
116 : : {
117 : 521876 : char firstpat;
118 : :
119 : : /*
120 : : * % processing is essentially a search for a text position at
121 : : * which the remainder of the text matches the remainder of the
122 : : * pattern, using a recursive call to check each potential match.
123 : : *
124 : : * If there are wildcards immediately following the %, we can skip
125 : : * over them first, using the idea that any sequence of N _'s and
126 : : * one or more %'s is equivalent to N _'s and one % (ie, it will
127 : : * match any sequence of at least N text characters). In this way
128 : : * we will always run the recursive search loop using a pattern
129 : : * fragment that begins with a literal character-to-match, thereby
130 : : * not recursing more than we have to.
131 : : */
132 : 521876 : NextByte(p, plen);
133 : :
134 [ # # + + : 521959 : while (plen > 0)
# # # # ]
135 : : {
136 [ # # + + : 429638 : if (*p == '%')
# # # # ]
137 : 3 : NextByte(p, plen);
138 [ # # + + : 429635 : else if (*p == '_')
# # # # ]
139 : : {
140 : : /* If not enough text left to match the pattern, ABORT */
141 [ # # + + : 81 : if (tlen <= 0)
# # # # ]
142 : 1 : return LIKE_ABORT;
143 [ + + - + ]: 80 : NextChar(t, tlen);
144 : 80 : NextByte(p, plen);
145 : 80 : }
146 : : else
147 : 429554 : break; /* Reached a non-wildcard pattern char */
148 : : }
149 : :
150 : : /*
151 : : * If we're at end of pattern, match: we have a trailing % which
152 : : * matches any remaining text string.
153 : : */
154 [ # # + + : 521875 : if (plen <= 0)
# # # # ]
155 : 92321 : return LIKE_TRUE;
156 : :
157 : : /*
158 : : * Otherwise, scan for a text position at which we can match the
159 : : * rest of the pattern. The first remaining pattern char is known
160 : : * to be a regular or escaped literal character, so we can compare
161 : : * the first pattern byte to each text byte to avoid recursing
162 : : * more than we have to. This fact also guarantees that we don't
163 : : * have to consider a match to the zero-length substring at the
164 : : * end of the text. With a nondeterministic collation, we can't
165 : : * rely on the first bytes being equal, so we have to recurse in
166 : : * any case.
167 : : */
168 [ # # - + : 429554 : if (*p == '\\')
# # # # ]
169 : : {
170 [ # # # # : 0 : if (plen < 2)
# # # # ]
171 [ # # # # : 0 : ereport(ERROR,
# # # # #
# # # # #
# # ]
172 : : (errcode(ERRCODE_INVALID_ESCAPE_SEQUENCE),
173 : : errmsg("LIKE pattern must not end with escape character")));
174 : 0 : firstpat = GETCHAR(p[1]);
175 : 0 : }
176 : : else
177 : 429554 : firstpat = GETCHAR(*p);
178 : :
179 [ # # + + : 40962091 : while (tlen > 0)
# # # # ]
180 : : {
181 [ # # # # : 40623991 : if (GETCHAR(*t) == firstpat || (locale && !locale->deterministic))
# # + + +
+ + + # #
# # # # #
# # # #
# ]
182 : : {
183 : 678407 : int matched = MatchText(t, tlen, p, plen, locale);
184 : :
185 [ # # + + : 678407 : if (matched != LIKE_FALSE)
# # # # ]
186 : 91454 : return matched; /* TRUE or ABORT */
187 [ # # + + : 678407 : }
# # # # ]
188 : :
189 [ + + + + ]: 40532545 : NextChar(t, tlen);
190 : : }
191 : :
192 : : /*
193 : : * End of text with no match, so no point in trying later places
194 : : * to start matching this pattern.
195 : : */
196 : 338100 : return LIKE_ABORT;
197 : 521876 : }
198 [ + + + + : 2677847 : else if (*p == '_')
# # + + ]
199 : : {
200 : : /* _ matches any single character, and we know there is one */
201 [ + + + + ]: 138488 : NextChar(t, tlen);
202 : 138485 : NextByte(p, plen);
203 : 138485 : continue;
204 : : }
205 [ - + # # : 2539362 : else if (locale && !locale->deterministic)
+ + + + #
# # # + -
+ - ]
206 : : {
207 : : /*
208 : : * For nondeterministic locales, we find the next substring of the
209 : : * pattern that does not contain wildcards and try to find a
210 : : * matching substring in the text. Crucially, we cannot do this
211 : : * character by character, as in the normal case, but must do it
212 : : * substring by substring, partitioned by the wildcard characters.
213 : : * (This is per SQL standard.)
214 : : */
215 : 47 : const char *p1;
216 : 47 : size_t p1len;
217 : 47 : const char *t1;
218 : 47 : size_t t1len;
219 : 47 : bool found_escape;
220 : 47 : const char *subpat;
221 : 47 : size_t subpatlen;
222 : 47 : char *buf = NULL;
223 : :
224 : : /*
225 : : * Determine next substring of pattern without wildcards. p is
226 : : * the start of the subpattern, p1 is one past the last byte. Also
227 : : * track if we found an escape character.
228 : : */
229 : 47 : p1 = p;
230 : 47 : p1len = plen;
231 : 47 : found_escape = false;
232 [ # # + + : 139 : while (p1len > 0)
# # # # ]
233 : : {
234 [ # # + + : 115 : if (*p1 == '\\')
# # # # ]
235 : : {
236 : 2 : found_escape = true;
237 : 2 : NextByte(p1, p1len);
238 [ # # + + : 2 : if (p1len == 0)
# # # # ]
239 [ # # # # : 1 : ereport(ERROR,
+ - + - #
# # # # #
# # ]
240 : : (errcode(ERRCODE_INVALID_ESCAPE_SEQUENCE),
241 : : errmsg("LIKE pattern must not end with escape character")));
242 : 1 : }
243 [ # # # # : 113 : else if (*p1 == '_' || *p1 == '%')
+ + + + #
# # # # #
# # ]
244 : 22 : break;
245 : 92 : NextByte(p1, p1len);
246 : : }
247 : :
248 : : /*
249 : : * If we found an escape character, then make an unescaped copy of
250 : : * the subpattern.
251 : : */
252 [ # # + + : 46 : if (found_escape)
# # # # ]
253 : : {
254 : 1 : char *b;
255 : :
256 : 1 : b = buf = palloc(p1 - p);
257 [ # # + + : 5 : for (const char *c = p; c < p1; c++)
# # # # ]
258 : : {
259 [ # # + + : 4 : if (*c == '\\')
# # # # ]
260 : : ;
261 : : else
262 : 3 : *(b++) = *c;
263 : 4 : }
264 : :
265 : 1 : subpat = buf;
266 : 1 : subpatlen = b - buf;
267 : 1 : }
268 : : else
269 : : {
270 : 45 : subpat = p;
271 : 45 : subpatlen = p1 - p;
272 : : }
273 : :
274 : : /*
275 : : * Shortcut: If this is the end of the pattern, then the rest of
276 : : * the text has to match the rest of the pattern.
277 : : */
278 [ # # + + : 46 : if (p1len == 0)
# # # # ]
279 : : {
280 : 24 : int cmp;
281 : :
282 : 24 : cmp = pg_strncoll(subpat, subpatlen, t, tlen, locale);
283 : :
284 [ # # + + : 24 : if (buf)
# # # # ]
285 : 1 : pfree(buf);
286 [ # # + + : 24 : if (cmp == 0)
# # # # ]
287 : 15 : return LIKE_TRUE;
288 : : else
289 : 9 : return LIKE_FALSE;
290 : 24 : }
291 : :
292 : : /*
293 : : * Now build a substring of the text and try to match it against
294 : : * the subpattern. t is the start of the text, t1 is one past the
295 : : * last byte. We start with a zero-length string.
296 : : */
297 : 22 : t1 = t;
298 : 22 : t1len = tlen;
299 : 65 : for (;;)
300 : : {
301 : 65 : int cmp;
302 : :
303 [ # # + - : 65 : CHECK_FOR_INTERRUPTS();
# # # # ]
304 : :
305 : 65 : cmp = pg_strncoll(subpat, subpatlen, t, (t1 - t), locale);
306 : :
307 : : /*
308 : : * If we found a match, we have to test if the rest of pattern
309 : : * can match against the rest of the string. Otherwise we
310 : : * have to continue here try matching with a longer substring.
311 : : * (This is similar to the recursion for the '%' wildcard
312 : : * above.)
313 : : *
314 : : * Note that we can't just wind forward p and t and continue
315 : : * with the main loop. This would fail for example with
316 : : *
317 : : * U&'\0061\0308bc' LIKE U&'\00E4_c' COLLATE ignore_accents
318 : : *
319 : : * You'd find that t=\0061 matches p=\00E4, but then the rest
320 : : * won't match; but t=\0061\0308 also matches p=\00E4, and
321 : : * then the rest will match.
322 : : */
323 [ # # + + : 65 : if (cmp == 0)
# # # # ]
324 : : {
325 : 17 : int matched = MatchText(t1, t1len, p1, p1len, locale);
326 : :
327 [ # # + + : 17 : if (matched == LIKE_TRUE)
# # # # ]
328 : : {
329 [ # # + - : 15 : if (buf)
# # # # ]
330 : 0 : pfree(buf);
331 : 15 : return matched;
332 : : }
333 [ # # + + : 17 : }
# # # # ]
334 : :
335 : : /*
336 : : * Didn't match. If we used up the whole text, then the match
337 : : * fails. Otherwise, try again with a longer substring.
338 : : */
339 [ # # + + : 50 : if (t1len == 0)
# # # # ]
340 : : {
341 [ # # + - : 7 : if (buf)
# # # # ]
342 : 0 : pfree(buf);
343 : 7 : return LIKE_FALSE;
344 : : }
345 : : else
346 [ + + + + ]: 48 : NextChar(t1, t1len);
347 [ # # + + : 65 : }
# # # # ]
348 : 46 : }
349 [ + - + + : 2539315 : else if (GETCHAR(*p) != GETCHAR(*t))
# # + + ]
350 : : {
351 : : /* non-wildcard pattern char fails to match text char */
352 : 697348 : return LIKE_FALSE;
353 : : }
354 : :
355 : : /*
356 : : * Pattern and text match, so advance.
357 : : *
358 : : * It is safe to use NextByte instead of NextChar here, even for
359 : : * multi-byte character sets, because we are not following immediately
360 : : * after a wildcard character. If we are in the middle of a multibyte
361 : : * character, we must already have matched at least one byte of the
362 : : * character from both text and pattern; so we cannot get out-of-sync
363 : : * on character boundaries. And we know that no backend-legal
364 : : * encoding allows ASCII characters such as '%' to appear as non-first
365 : : * bytes of characters, so we won't mistakenly detect a new wildcard.
366 : : */
367 : 1843545 : NextByte(t, tlen);
368 : 1843545 : NextByte(p, plen);
369 : : }
370 : :
371 [ - + + + : 1577 : if (tlen > 0)
# # - + ]
372 : 51 : return LIKE_FALSE; /* end of pattern, but not of text */
373 : :
374 : : /*
375 : : * End of text, but perhaps not of pattern. Match iff the remaining
376 : : * pattern can match a zero-length string, ie, it's zero or more %'s.
377 : : */
378 [ - + - + : 1605 : while (plen > 0 && *p == '%')
+ + + + #
# # # + +
- + ]
379 : 79 : NextByte(p, plen);
380 [ + - + + : 1526 : if (plen <= 0)
# # + + ]
381 : 730 : return LIKE_TRUE;
382 : :
383 : : /*
384 : : * End of text with no match, so no point in trying later places to start
385 : : * matching this pattern.
386 : : */
387 : 796 : return LIKE_ABORT;
388 : 1221426 : } /* MatchText() */
389 : :
390 : : /*
391 : : * like_escape() --- given a pattern and an ESCAPE string,
392 : : * convert the pattern to use Postgres' standard backslash escape convention.
393 : : */
394 : : #ifdef do_like_escape
395 : :
396 : : static text *
397 : 32 : do_like_escape(text *pat, text *esc)
398 : : {
399 : 32 : text *result;
400 : 32 : char *p,
401 : : *e,
402 : : *r;
403 : 32 : int plen,
404 : : elen;
405 : 32 : bool afterescape;
406 : :
407 : 32 : p = VARDATA_ANY(pat);
408 : 32 : plen = VARSIZE_ANY_EXHDR(pat);
409 : 32 : e = VARDATA_ANY(esc);
410 : 32 : elen = VARSIZE_ANY_EXHDR(esc);
411 : :
412 : : /*
413 : : * Worst-case pattern growth is 2x --- unlikely, but it's hardly worth
414 : : * trying to calculate the size more accurately than that.
415 : : */
416 : 32 : result = (text *) palloc(plen * 2 + VARHDRSZ);
417 : 32 : r = VARDATA(result);
418 : :
419 [ - + + - ]: 32 : if (elen == 0)
420 : : {
421 : : /*
422 : : * No escape character is wanted. Double any backslashes in the
423 : : * pattern to make them act like ordinary characters.
424 : : */
425 [ # # # # ]: 0 : while (plen > 0)
426 : : {
427 [ # # # # ]: 0 : if (*p == '\\')
428 : 0 : *r++ = '\\';
429 [ # # ]: 0 : CopyAdvChar(r, p, plen);
430 : : }
431 : 0 : }
432 : : else
433 : : {
434 : : /*
435 : : * The specified escape must be only a single character.
436 : : */
437 : 32 : NextChar(e, elen);
438 [ + - + - ]: 32 : if (elen != 0)
439 [ # # # # : 0 : ereport(ERROR,
# # # # ]
440 : : (errcode(ERRCODE_INVALID_ESCAPE_SEQUENCE),
441 : : errmsg("invalid escape string"),
442 : : errhint("Escape string must be empty or one character.")));
443 : :
444 : 32 : e = VARDATA_ANY(esc);
445 : :
446 : : /*
447 : : * If specified escape is '\', just copy the pattern as-is.
448 : : */
449 [ - + - + ]: 32 : if (*e == '\\')
450 : : {
451 : 0 : memcpy(result, pat, VARSIZE_ANY(pat));
452 : 0 : return result;
453 : : }
454 : :
455 : : /*
456 : : * Otherwise, convert occurrences of the specified escape character to
457 : : * '\', and double occurrences of '\' --- unless they immediately
458 : : * follow an escape character!
459 : : */
460 : 32 : afterescape = false;
461 [ + + + + ]: 194 : while (plen > 0)
462 : : {
463 [ + + + - : 162 : if (CHAREQ(p, e) && !afterescape)
+ + + + ]
464 : : {
465 : 32 : *r++ = '\\';
466 : 32 : NextChar(p, plen);
467 : 32 : afterescape = true;
468 : 32 : }
469 [ - + - + ]: 130 : else if (*p == '\\')
470 : : {
471 : 0 : *r++ = '\\';
472 [ # # # # ]: 0 : if (!afterescape)
473 : 0 : *r++ = '\\';
474 : 0 : NextChar(p, plen);
475 : 0 : afterescape = false;
476 : 0 : }
477 : : else
478 : : {
479 [ + + ]: 254 : CopyAdvChar(r, p, plen);
480 : 130 : afterescape = false;
481 : : }
482 : : }
483 : : }
484 : :
485 : 32 : SET_VARSIZE(result, r - ((char *) result));
486 : :
487 : 32 : return result;
488 : 32 : }
489 : : #endif /* do_like_escape */
490 : :
491 : : #ifdef CHAREQ
492 : : #undef CHAREQ
493 : : #endif
494 : :
495 : : #undef NextChar
496 : : #undef CopyAdvChar
497 : : #undef MatchText
498 : :
499 : : #ifdef do_like_escape
500 : : #undef do_like_escape
501 : : #endif
502 : :
503 : : #undef GETCHAR
504 : :
505 : : #ifdef MATCH_LOWER
506 : : #undef MATCH_LOWER
507 : :
508 : : #endif
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