1 /*-------------------------------------------------------------------------
2 *
3 * tsquery_rewrite.c
4 * Utilities for reconstructing tsquery
5 *
6 * Portions Copyright (c) 1996-2020, PostgreSQL Global Development Group
7 *
8 *
9 * IDENTIFICATION
10 * src/backend/utils/adt/tsquery_rewrite.c
11 *
12 *-------------------------------------------------------------------------
13 */
14
15 #include "postgres.h"
16
17 #include "catalog/pg_type.h"
18 #include "executor/spi.h"
19 #include "miscadmin.h"
20 #include "tsearch/ts_utils.h"
21 #include "utils/builtins.h"
22
23
24 /*
25 * If "node" is equal to "ex", return a copy of "subs" instead.
26 * If "ex" matches a subset of node's children, return a modified version
27 * of "node" in which those children are replaced with a copy of "subs".
28 * Otherwise return "node" unmodified.
29 *
30 * The QTN_NOCHANGE bit is set in successfully modified nodes, so that
31 * we won't uselessly recurse into them.
32 * Also, set *isfind true if we make a replacement.
33 */
34 static QTNode *
findeq(QTNode * node,QTNode * ex,QTNode * subs,bool * isfind)35 findeq(QTNode *node, QTNode *ex, QTNode *subs, bool *isfind)
36 {
37 /* Can't match unless signature matches and node type matches. */
38 if ((node->sign & ex->sign) != ex->sign ||
39 node->valnode->type != ex->valnode->type)
40 return node;
41
42 /* Ignore nodes marked NOCHANGE, too. */
43 if (node->flags & QTN_NOCHANGE)
44 return node;
45
46 if (node->valnode->type == QI_OPR)
47 {
48 /* Must be same operator. */
49 if (node->valnode->qoperator.oper != ex->valnode->qoperator.oper)
50 return node;
51
52 if (node->nchild == ex->nchild)
53 {
54 /*
55 * Simple case: when same number of children, match if equal.
56 * (This is reliable when the children were sorted earlier.)
57 */
58 if (QTNEq(node, ex))
59 {
60 /* Match; delete node and return a copy of subs instead. */
61 QTNFree(node);
62 if (subs)
63 {
64 node = QTNCopy(subs);
65 node->flags |= QTN_NOCHANGE;
66 }
67 else
68 node = NULL;
69 *isfind = true;
70 }
71 }
72 else if (node->nchild > ex->nchild && ex->nchild > 0)
73 {
74 /*
75 * AND and OR are commutative/associative, so we should check if a
76 * subset of the children match. For example, if node is A|B|C,
77 * and ex is B|C, we have a match after we notionally convert node
78 * to A|(B|C). This does not work for NOT or PHRASE nodes, but we
79 * can't get here for those node types because they have a fixed
80 * number of children.
81 *
82 * Because we expect that the children are sorted, it suffices to
83 * make one pass through the two lists to find the matches.
84 */
85 bool *matched;
86 int nmatched;
87 int i,
88 j;
89
90 /* Assert that the subset rule is OK */
91 Assert(node->valnode->qoperator.oper == OP_AND ||
92 node->valnode->qoperator.oper == OP_OR);
93
94 /* matched[] will record which children of node matched */
95 matched = (bool *) palloc0(node->nchild * sizeof(bool));
96 nmatched = 0;
97 i = j = 0;
98 while (i < node->nchild && j < ex->nchild)
99 {
100 int cmp = QTNodeCompare(node->child[i], ex->child[j]);
101
102 if (cmp == 0)
103 {
104 /* match! */
105 matched[i] = true;
106 nmatched++;
107 i++, j++;
108 }
109 else if (cmp < 0)
110 {
111 /* node->child[i] has no match, ignore it */
112 i++;
113 }
114 else
115 {
116 /* ex->child[j] has no match; we can give up immediately */
117 break;
118 }
119 }
120
121 if (nmatched == ex->nchild)
122 {
123 /* collapse out the matched children of node */
124 j = 0;
125 for (i = 0; i < node->nchild; i++)
126 {
127 if (matched[i])
128 QTNFree(node->child[i]);
129 else
130 node->child[j++] = node->child[i];
131 }
132
133 /* and instead insert a copy of subs */
134 if (subs)
135 {
136 subs = QTNCopy(subs);
137 subs->flags |= QTN_NOCHANGE;
138 node->child[j++] = subs;
139 }
140
141 node->nchild = j;
142
143 /*
144 * At this point we might have a node with zero or one child,
145 * which should be simplified. But we leave it to our caller
146 * (dofindsubquery) to take care of that.
147 */
148
149 /*
150 * Re-sort the node to put new child in the right place. This
151 * is a bit bogus, because it won't matter for findsubquery's
152 * remaining processing, and it's insufficient to prepare the
153 * tree for another search (we would need to re-flatten as
154 * well, and we don't want to do that because we'd lose the
155 * QTN_NOCHANGE marking on the new child). But it's needed to
156 * keep the results the same as the regression tests expect.
157 */
158 QTNSort(node);
159
160 *isfind = true;
161 }
162
163 pfree(matched);
164 }
165 }
166 else
167 {
168 Assert(node->valnode->type == QI_VAL);
169
170 if (node->valnode->qoperand.valcrc != ex->valnode->qoperand.valcrc)
171 return node;
172 else if (QTNEq(node, ex))
173 {
174 QTNFree(node);
175 if (subs)
176 {
177 node = QTNCopy(subs);
178 node->flags |= QTN_NOCHANGE;
179 }
180 else
181 {
182 node = NULL;
183 }
184 *isfind = true;
185 }
186 }
187
188 return node;
189 }
190
191 /*
192 * Recursive guts of findsubquery(): attempt to replace "ex" with "subs"
193 * at the root node, and if we failed to do so, recursively match against
194 * child nodes.
195 *
196 * Delete any void subtrees resulting from the replacement.
197 * In the following example '5' is replaced by empty operand:
198 *
199 * AND -> 6
200 * / \
201 * 5 OR
202 * / \
203 * 6 5
204 */
205 static QTNode *
dofindsubquery(QTNode * root,QTNode * ex,QTNode * subs,bool * isfind)206 dofindsubquery(QTNode *root, QTNode *ex, QTNode *subs, bool *isfind)
207 {
208 /* since this function recurses, it could be driven to stack overflow. */
209 check_stack_depth();
210
211 /* also, since it's a bit expensive, let's check for query cancel. */
212 CHECK_FOR_INTERRUPTS();
213
214 /* match at the node itself */
215 root = findeq(root, ex, subs, isfind);
216
217 /* unless we matched here, consider matches at child nodes */
218 if (root && (root->flags & QTN_NOCHANGE) == 0 &&
219 root->valnode->type == QI_OPR)
220 {
221 int i,
222 j = 0;
223
224 /*
225 * Any subtrees that are replaced by NULL must be dropped from the
226 * tree.
227 */
228 for (i = 0; i < root->nchild; i++)
229 {
230 root->child[j] = dofindsubquery(root->child[i], ex, subs, isfind);
231 if (root->child[j])
232 j++;
233 }
234
235 root->nchild = j;
236
237 /*
238 * If we have just zero or one remaining child node, simplify out this
239 * operator node.
240 */
241 if (root->nchild == 0)
242 {
243 QTNFree(root);
244 root = NULL;
245 }
246 else if (root->nchild == 1 && root->valnode->qoperator.oper != OP_NOT)
247 {
248 QTNode *nroot = root->child[0];
249
250 pfree(root);
251 root = nroot;
252 }
253 }
254
255 return root;
256 }
257
258 /*
259 * Substitute "subs" for "ex" throughout the QTNode tree at root.
260 *
261 * If isfind isn't NULL, set *isfind to show whether we made any substitution.
262 *
263 * Both "root" and "ex" must have been through QTNTernary and QTNSort
264 * to ensure reliable matching.
265 */
266 QTNode *
findsubquery(QTNode * root,QTNode * ex,QTNode * subs,bool * isfind)267 findsubquery(QTNode *root, QTNode *ex, QTNode *subs, bool *isfind)
268 {
269 bool DidFind = false;
270
271 root = dofindsubquery(root, ex, subs, &DidFind);
272
273 if (isfind)
274 *isfind = DidFind;
275
276 return root;
277 }
278
279 Datum
tsquery_rewrite_query(PG_FUNCTION_ARGS)280 tsquery_rewrite_query(PG_FUNCTION_ARGS)
281 {
282 TSQuery query = PG_GETARG_TSQUERY_COPY(0);
283 text *in = PG_GETARG_TEXT_PP(1);
284 TSQuery rewrited = query;
285 MemoryContext outercontext = CurrentMemoryContext;
286 MemoryContext oldcontext;
287 QTNode *tree;
288 char *buf;
289 SPIPlanPtr plan;
290 Portal portal;
291 bool isnull;
292
293 if (query->size == 0)
294 {
295 PG_FREE_IF_COPY(in, 1);
296 PG_RETURN_POINTER(rewrited);
297 }
298
299 tree = QT2QTN(GETQUERY(query), GETOPERAND(query));
300 QTNTernary(tree);
301 QTNSort(tree);
302
303 buf = text_to_cstring(in);
304
305 SPI_connect();
306
307 if ((plan = SPI_prepare(buf, 0, NULL)) == NULL)
308 elog(ERROR, "SPI_prepare(\"%s\") failed", buf);
309
310 if ((portal = SPI_cursor_open(NULL, plan, NULL, NULL, true)) == NULL)
311 elog(ERROR, "SPI_cursor_open(\"%s\") failed", buf);
312
313 SPI_cursor_fetch(portal, true, 100);
314
315 if (SPI_tuptable == NULL ||
316 SPI_tuptable->tupdesc->natts != 2 ||
317 SPI_gettypeid(SPI_tuptable->tupdesc, 1) != TSQUERYOID ||
318 SPI_gettypeid(SPI_tuptable->tupdesc, 2) != TSQUERYOID)
319 ereport(ERROR,
320 (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
321 errmsg("ts_rewrite query must return two tsquery columns")));
322
323 while (SPI_processed > 0 && tree)
324 {
325 uint64 i;
326
327 for (i = 0; i < SPI_processed && tree; i++)
328 {
329 Datum qdata = SPI_getbinval(SPI_tuptable->vals[i], SPI_tuptable->tupdesc, 1, &isnull);
330 Datum sdata;
331
332 if (isnull)
333 continue;
334
335 sdata = SPI_getbinval(SPI_tuptable->vals[i], SPI_tuptable->tupdesc, 2, &isnull);
336
337 if (!isnull)
338 {
339 TSQuery qtex = DatumGetTSQuery(qdata);
340 TSQuery qtsubs = DatumGetTSQuery(sdata);
341 QTNode *qex,
342 *qsubs = NULL;
343
344 if (qtex->size == 0)
345 {
346 if (qtex != (TSQuery) DatumGetPointer(qdata))
347 pfree(qtex);
348 if (qtsubs != (TSQuery) DatumGetPointer(sdata))
349 pfree(qtsubs);
350 continue;
351 }
352
353 qex = QT2QTN(GETQUERY(qtex), GETOPERAND(qtex));
354
355 QTNTernary(qex);
356 QTNSort(qex);
357
358 if (qtsubs->size)
359 qsubs = QT2QTN(GETQUERY(qtsubs), GETOPERAND(qtsubs));
360
361 oldcontext = MemoryContextSwitchTo(outercontext);
362 tree = findsubquery(tree, qex, qsubs, NULL);
363 MemoryContextSwitchTo(oldcontext);
364
365 QTNFree(qex);
366 if (qtex != (TSQuery) DatumGetPointer(qdata))
367 pfree(qtex);
368 QTNFree(qsubs);
369 if (qtsubs != (TSQuery) DatumGetPointer(sdata))
370 pfree(qtsubs);
371
372 if (tree)
373 {
374 /* ready the tree for another pass */
375 QTNClearFlags(tree, QTN_NOCHANGE);
376 QTNTernary(tree);
377 QTNSort(tree);
378 }
379 }
380 }
381
382 SPI_freetuptable(SPI_tuptable);
383 SPI_cursor_fetch(portal, true, 100);
384 }
385
386 SPI_freetuptable(SPI_tuptable);
387 SPI_cursor_close(portal);
388 SPI_freeplan(plan);
389 SPI_finish();
390
391 if (tree)
392 {
393 QTNBinary(tree);
394 rewrited = QTN2QT(tree);
395 QTNFree(tree);
396 PG_FREE_IF_COPY(query, 0);
397 }
398 else
399 {
400 SET_VARSIZE(rewrited, HDRSIZETQ);
401 rewrited->size = 0;
402 }
403
404 pfree(buf);
405 PG_FREE_IF_COPY(in, 1);
406 PG_RETURN_POINTER(rewrited);
407 }
408
409 Datum
tsquery_rewrite(PG_FUNCTION_ARGS)410 tsquery_rewrite(PG_FUNCTION_ARGS)
411 {
412 TSQuery query = PG_GETARG_TSQUERY_COPY(0);
413 TSQuery ex = PG_GETARG_TSQUERY(1);
414 TSQuery subst = PG_GETARG_TSQUERY(2);
415 TSQuery rewrited = query;
416 QTNode *tree,
417 *qex,
418 *subs = NULL;
419
420 if (query->size == 0 || ex->size == 0)
421 {
422 PG_FREE_IF_COPY(ex, 1);
423 PG_FREE_IF_COPY(subst, 2);
424 PG_RETURN_POINTER(rewrited);
425 }
426
427 tree = QT2QTN(GETQUERY(query), GETOPERAND(query));
428 QTNTernary(tree);
429 QTNSort(tree);
430
431 qex = QT2QTN(GETQUERY(ex), GETOPERAND(ex));
432 QTNTernary(qex);
433 QTNSort(qex);
434
435 if (subst->size)
436 subs = QT2QTN(GETQUERY(subst), GETOPERAND(subst));
437
438 tree = findsubquery(tree, qex, subs, NULL);
439
440 QTNFree(qex);
441 QTNFree(subs);
442
443 if (!tree)
444 {
445 SET_VARSIZE(rewrited, HDRSIZETQ);
446 rewrited->size = 0;
447 PG_FREE_IF_COPY(ex, 1);
448 PG_FREE_IF_COPY(subst, 2);
449 PG_RETURN_POINTER(rewrited);
450 }
451 else
452 {
453 QTNBinary(tree);
454 rewrited = QTN2QT(tree);
455 QTNFree(tree);
456 }
457
458 PG_FREE_IF_COPY(query, 0);
459 PG_FREE_IF_COPY(ex, 1);
460 PG_FREE_IF_COPY(subst, 2);
461 PG_RETURN_POINTER(rewrited);
462 }
463