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) 1996-2025, 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 : #ifdef MATCH_LOWER
74 : #define GETCHAR(t, locale) MATCH_LOWER(t, locale)
75 : #else
76 : #define GETCHAR(t, locale) (t)
77 : #endif
78 :
79 : static int
80 1266368 : MatchText(const char *t, int tlen, const char *p, int plen, pg_locale_t locale)
81 : {
82 : /* Fast path for match-everything pattern */
83 1266368 : if (plen == 1 && *p == '%')
84 244 : return LIKE_TRUE;
85 :
86 : /* Since this function recurses, it could be driven to stack overflow */
87 1266124 : check_stack_depth();
88 :
89 : /*
90 : * In this loop, we advance by char when matching wildcards (and thus on
91 : * recursive entry to this function we are properly char-synced). On other
92 : * occasions it is safe to advance by byte, as the text and pattern will
93 : * be in lockstep. This allows us to perform all comparisons between the
94 : * text and pattern on a byte by byte basis, even for multi-byte
95 : * encodings.
96 : */
97 1907838 : while (tlen > 0 && plen > 0)
98 : {
99 1897254 : if (*p == '\\')
100 : {
101 : /* Next pattern byte must match literally, whatever it is */
102 12838 : NextByte(p, plen);
103 : /* ... and there had better be one, per SQL standard */
104 12838 : if (plen <= 0)
105 0 : ereport(ERROR,
106 : (errcode(ERRCODE_INVALID_ESCAPE_SEQUENCE),
107 : errmsg("LIKE pattern must not end with escape character")));
108 12838 : if (GETCHAR(*p, locale) != GETCHAR(*t, locale))
109 3444 : return LIKE_FALSE;
110 : }
111 1884416 : else if (*p == '%')
112 : {
113 : char firstpat;
114 :
115 : /*
116 : * % processing is essentially a search for a text position at
117 : * which the remainder of the text matches the remainder of the
118 : * pattern, using a recursive call to check each potential match.
119 : *
120 : * If there are wildcards immediately following the %, we can skip
121 : * over them first, using the idea that any sequence of N _'s and
122 : * one or more %'s is equivalent to N _'s and one % (ie, it will
123 : * match any sequence of at least N text characters). In this way
124 : * we will always run the recursive search loop using a pattern
125 : * fragment that begins with a literal character-to-match, thereby
126 : * not recursing more than we have to.
127 : */
128 169086 : NextByte(p, plen);
129 :
130 169594 : while (plen > 0)
131 : {
132 132140 : if (*p == '%')
133 18 : NextByte(p, plen);
134 132122 : else if (*p == '_')
135 : {
136 : /* If not enough text left to match the pattern, ABORT */
137 496 : if (tlen <= 0)
138 6 : return LIKE_ABORT;
139 490 : NextChar(t, tlen);
140 490 : NextByte(p, plen);
141 : }
142 : else
143 131626 : break; /* Reached a non-wildcard pattern char */
144 : }
145 :
146 : /*
147 : * If we're at end of pattern, match: we have a trailing % which
148 : * matches any remaining text string.
149 : */
150 169080 : if (plen <= 0)
151 37454 : return LIKE_TRUE;
152 :
153 : /*
154 : * Otherwise, scan for a text position at which we can match the
155 : * rest of the pattern. The first remaining pattern char is known
156 : * to be a regular or escaped literal character, so we can compare
157 : * the first pattern byte to each text byte to avoid recursing
158 : * more than we have to. This fact also guarantees that we don't
159 : * have to consider a match to the zero-length substring at the
160 : * end of the text. With a nondeterministic collation, we can't
161 : * rely on the first bytes being equal, so we have to recurse in
162 : * any case.
163 : */
164 131626 : if (*p == '\\')
165 : {
166 4 : if (plen < 2)
167 0 : ereport(ERROR,
168 : (errcode(ERRCODE_INVALID_ESCAPE_SEQUENCE),
169 : errmsg("LIKE pattern must not end with escape character")));
170 4 : firstpat = GETCHAR(p[1], locale);
171 : }
172 : else
173 131622 : firstpat = GETCHAR(*p, locale);
174 :
175 3840820 : while (tlen > 0)
176 : {
177 3738226 : if (GETCHAR(*t, locale) == firstpat || (locale && !locale->deterministic))
178 : {
179 107688 : int matched = MatchText(t, tlen, p, plen, locale);
180 :
181 107688 : if (matched != LIKE_FALSE)
182 29032 : return matched; /* TRUE or ABORT */
183 : }
184 :
185 3709242 : NextChar(t, tlen);
186 : }
187 :
188 : /*
189 : * End of text with no match, so no point in trying later places
190 : * to start matching this pattern.
191 : */
192 102594 : return LIKE_ABORT;
193 : }
194 1715330 : else if (*p == '_')
195 : {
196 : /* _ matches any single character, and we know there is one */
197 16490 : NextChar(t, tlen);
198 16472 : NextByte(p, plen);
199 16472 : continue;
200 : }
201 1698858 : else if (locale && !locale->deterministic)
202 : {
203 : /*
204 : * For nondeterministic locales, we find the next substring of the
205 : * pattern that does not contain wildcards and try to find a
206 : * matching substring in the text. Crucially, we cannot do this
207 : * character by character, as in the normal case, but must do it
208 : * substring by substring, partitioned by the wildcard characters.
209 : * (This is per SQL standard.)
210 : */
211 : const char *p1;
212 : size_t p1len;
213 : const char *t1;
214 : size_t t1len;
215 : bool found_escape;
216 : const char *subpat;
217 : size_t subpatlen;
218 282 : char *buf = NULL;
219 :
220 : /*
221 : * Determine next substring of pattern without wildcards. p is
222 : * the start of the subpattern, p1 is one past the last byte. Also
223 : * track if we found an escape character.
224 : */
225 282 : p1 = p;
226 282 : p1len = plen;
227 282 : found_escape = false;
228 834 : while (p1len > 0)
229 : {
230 690 : if (*p1 == '\\')
231 : {
232 12 : found_escape = true;
233 12 : NextByte(p1, p1len);
234 12 : if (p1len == 0)
235 6 : ereport(ERROR,
236 : (errcode(ERRCODE_INVALID_ESCAPE_SEQUENCE),
237 : errmsg("LIKE pattern must not end with escape character")));
238 : }
239 678 : else if (*p1 == '_' || *p1 == '%')
240 : break;
241 552 : NextByte(p1, p1len);
242 : }
243 :
244 : /*
245 : * If we found an escape character, then make an unescaped copy of
246 : * the subpattern.
247 : */
248 276 : if (found_escape)
249 : {
250 : char *b;
251 :
252 6 : b = buf = palloc(p1 - p);
253 30 : for (const char *c = p; c < p1; c++)
254 : {
255 24 : if (*c == '\\')
256 : ;
257 : else
258 18 : *(b++) = *c;
259 : }
260 :
261 6 : subpat = buf;
262 6 : subpatlen = b - buf;
263 : }
264 : else
265 : {
266 270 : subpat = p;
267 270 : subpatlen = p1 - p;
268 : }
269 :
270 : /*
271 : * Shortcut: If this is the end of the pattern, then the rest of
272 : * the text has to match the rest of the pattern.
273 : */
274 276 : if (p1len == 0)
275 : {
276 : int cmp;
277 :
278 144 : cmp = pg_strncoll(subpat, subpatlen, t, tlen, locale);
279 :
280 144 : if (buf)
281 6 : pfree(buf);
282 144 : if (cmp == 0)
283 90 : return LIKE_TRUE;
284 : else
285 54 : return LIKE_FALSE;
286 : }
287 :
288 : /*
289 : * Now build a substring of the text and try to match it against
290 : * the subpattern. t is the start of the text, t1 is one past the
291 : * last byte. We start with a zero-length string.
292 : */
293 132 : t1 = t;
294 132 : t1len = tlen;
295 : for (;;)
296 258 : {
297 : int cmp;
298 :
299 390 : CHECK_FOR_INTERRUPTS();
300 :
301 390 : cmp = pg_strncoll(subpat, subpatlen, t, (t1 - t), locale);
302 :
303 : /*
304 : * If we found a match, we have to test if the rest of pattern
305 : * can match against the rest of the string. Otherwise we
306 : * have to continue here try matching with a longer substring.
307 : * (This is similar to the recursion for the '%' wildcard
308 : * above.)
309 : *
310 : * Note that we can't just wind forward p and t and continue
311 : * with the main loop. This would fail for example with
312 : *
313 : * U&'\0061\0308bc' LIKE U&'\00E4_c' COLLATE ignore_accents
314 : *
315 : * You'd find that t=\0061 matches p=\00E4, but then the rest
316 : * won't match; but t=\0061\0308 also matches p=\00E4, and
317 : * then the rest will match.
318 : */
319 390 : if (cmp == 0)
320 : {
321 102 : int matched = MatchText(t1, t1len, p1, p1len, locale);
322 :
323 102 : if (matched == LIKE_TRUE)
324 : {
325 90 : if (buf)
326 0 : pfree(buf);
327 90 : return matched;
328 : }
329 : }
330 :
331 : /*
332 : * Didn't match. If we used up the whole text, then the match
333 : * fails. Otherwise, try again with a longer substring.
334 : */
335 300 : if (t1len == 0)
336 : {
337 42 : if (buf)
338 0 : pfree(buf);
339 42 : return LIKE_FALSE;
340 : }
341 : else
342 288 : NextChar(t1, t1len);
343 : }
344 : }
345 1698576 : else if (GETCHAR(*p, locale) != GETCHAR(*t, locale))
346 : {
347 : /* non-wildcard pattern char fails to match text char */
348 1082728 : return LIKE_FALSE;
349 : }
350 :
351 : /*
352 : * Pattern and text match, so advance.
353 : *
354 : * It is safe to use NextByte instead of NextChar here, even for
355 : * multi-byte character sets, because we are not following immediately
356 : * after a wildcard character. If we are in the middle of a multibyte
357 : * character, we must already have matched at least one byte of the
358 : * character from both text and pattern; so we cannot get out-of-sync
359 : * on character boundaries. And we know that no backend-legal
360 : * encoding allows ASCII characters such as '%' to appear as non-first
361 : * bytes of characters, so we won't mistakenly detect a new wildcard.
362 : */
363 625242 : NextByte(t, tlen);
364 625242 : NextByte(p, plen);
365 : }
366 :
367 10584 : if (tlen > 0)
368 318 : return LIKE_FALSE; /* end of pattern, but not of text */
369 :
370 : /*
371 : * End of text, but perhaps not of pattern. Match iff the remaining
372 : * pattern can match a zero-length string, ie, it's zero or more %'s.
373 : */
374 10856 : while (plen > 0 && *p == '%')
375 590 : NextByte(p, plen);
376 10266 : if (plen <= 0)
377 4662 : return LIKE_TRUE;
378 :
379 : /*
380 : * End of text with no match, so no point in trying later places to start
381 : * matching this pattern.
382 : */
383 5604 : return LIKE_ABORT;
384 : } /* MatchText() */
385 :
386 : /*
387 : * like_escape() --- given a pattern and an ESCAPE string,
388 : * convert the pattern to use Postgres' standard backslash escape convention.
389 : */
390 : #ifdef do_like_escape
391 :
392 : static text *
393 224 : do_like_escape(text *pat, text *esc)
394 : {
395 : text *result;
396 : char *p,
397 : *e,
398 : *r;
399 : int plen,
400 : elen;
401 : bool afterescape;
402 :
403 224 : p = VARDATA_ANY(pat);
404 224 : plen = VARSIZE_ANY_EXHDR(pat);
405 224 : e = VARDATA_ANY(esc);
406 224 : elen = VARSIZE_ANY_EXHDR(esc);
407 :
408 : /*
409 : * Worst-case pattern growth is 2x --- unlikely, but it's hardly worth
410 : * trying to calculate the size more accurately than that.
411 : */
412 224 : result = (text *) palloc(plen * 2 + VARHDRSZ);
413 224 : r = VARDATA(result);
414 :
415 224 : if (elen == 0)
416 : {
417 : /*
418 : * No escape character is wanted. Double any backslashes in the
419 : * pattern to make them act like ordinary characters.
420 : */
421 128 : while (plen > 0)
422 : {
423 96 : if (*p == '\\')
424 0 : *r++ = '\\';
425 192 : CopyAdvChar(r, p, plen);
426 : }
427 : }
428 : else
429 : {
430 : /*
431 : * The specified escape must be only a single character.
432 : */
433 192 : NextChar(e, elen);
434 192 : if (elen != 0)
435 0 : ereport(ERROR,
436 : (errcode(ERRCODE_INVALID_ESCAPE_SEQUENCE),
437 : errmsg("invalid escape string"),
438 : errhint("Escape string must be empty or one character.")));
439 :
440 192 : e = VARDATA_ANY(esc);
441 :
442 : /*
443 : * If specified escape is '\', just copy the pattern as-is.
444 : */
445 192 : if (*e == '\\')
446 : {
447 0 : memcpy(result, pat, VARSIZE_ANY(pat));
448 0 : return result;
449 : }
450 :
451 : /*
452 : * Otherwise, convert occurrences of the specified escape character to
453 : * '\', and double occurrences of '\' --- unless they immediately
454 : * follow an escape character!
455 : */
456 192 : afterescape = false;
457 1164 : while (plen > 0)
458 : {
459 972 : if (CHAREQ(p, e) && !afterescape)
460 : {
461 192 : *r++ = '\\';
462 192 : NextChar(p, plen);
463 192 : afterescape = true;
464 : }
465 780 : else if (*p == '\\')
466 : {
467 0 : *r++ = '\\';
468 0 : if (!afterescape)
469 0 : *r++ = '\\';
470 0 : NextChar(p, plen);
471 0 : afterescape = false;
472 : }
473 : else
474 : {
475 1524 : CopyAdvChar(r, p, plen);
476 780 : afterescape = false;
477 : }
478 : }
479 : }
480 :
481 224 : SET_VARSIZE(result, r - ((char *) result));
482 :
483 224 : return result;
484 : }
485 : #endif /* do_like_escape */
486 :
487 : #ifdef CHAREQ
488 : #undef CHAREQ
489 : #endif
490 :
491 : #undef NextChar
492 : #undef CopyAdvChar
493 : #undef MatchText
494 :
495 : #ifdef do_like_escape
496 : #undef do_like_escape
497 : #endif
498 :
499 : #undef GETCHAR
500 :
501 : #ifdef MATCH_LOWER
502 : #undef MATCH_LOWER
503 :
504 : #endif
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