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Commitc8bfe05

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Prevent crash when ts_rewrite() replaces a non-top-level subtree with null.
When ts_rewrite()'s replacement argument is an empty tsquery, it's supposedto simplify any operator nodes whose operand(s) become NULL; but it failedto do that reliably, because dropvoidsubtree() only examined the top levelof the result tree. Rather than make a second recursive pass, let's justgive the responsibility to dofindsubquery() to simplify while it's doingthe main replacement pass. Per report from Andreas Seltenreich.Artur Zakirov, with some cosmetic changes by me. Back-patch to allsupported branches.Discussion:https://postgr.es/m/8737i01dew.fsf@credativ.de
1 parentb90f224 commitc8bfe05

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3 files changed

+47
-29
lines changed

3 files changed

+47
-29
lines changed

‎src/backend/utils/adt/tsquery_rewrite.c‎

Lines changed: 29 additions & 29 deletions
Original file line numberDiff line numberDiff line change
@@ -140,6 +140,12 @@ findeq(QTNode *node, QTNode *ex, QTNode *subs, bool *isfind)
140140

141141
node->nchild=j;
142142

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+
143149
/*
144150
* Re-sort the node to put new child in the right place. This
145151
* is a bit bogus, because it won't matter for findsubquery's
@@ -186,6 +192,15 @@ findeq(QTNode *node, QTNode *ex, QTNode *subs, bool *isfind)
186192
* Recursive guts of findsubquery(): attempt to replace "ex" with "subs"
187193
* at the root node, and if we failed to do so, recursively match against
188194
* 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+
* 65
189204
*/
190205
staticQTNode*
191206
dofindsubquery(QTNode*root,QTNode*ex,QTNode*subs,bool*isfind)
@@ -196,45 +211,33 @@ dofindsubquery(QTNode *root, QTNode *ex, QTNode *subs, bool *isfind)
196211
/* also, since it's a bit expensive, let's check for query cancel. */
197212
CHECK_FOR_INTERRUPTS();
198213

214+
/* match at the node itself */
199215
root=findeq(root,ex,subs,isfind);
200216

201-
if (root&& (root->flags&QTN_NOCHANGE)==0&&root->valnode->type==QI_OPR)
202-
{
203-
inti;
204-
205-
for (i=0;i<root->nchild;i++)
206-
root->child[i]=dofindsubquery(root->child[i],ex,subs,isfind);
207-
}
208-
209-
returnroot;
210-
}
211-
212-
/*
213-
* Delete any void subtrees that may have been inserted when the replacement
214-
* subtree is void.
215-
*/
216-
staticQTNode*
217-
dropvoidsubtree(QTNode*root)
218-
{
219-
if (!root)
220-
returnNULL;
221-
222-
if (root->valnode->type==QI_OPR)
217+
/* unless we matched here, consider matches at child nodes */
218+
if (root&& (root->flags&QTN_NOCHANGE)==0&&
219+
root->valnode->type==QI_OPR)
223220
{
224221
inti,
225222
j=0;
226223

224+
/*
225+
* Any subtrees that are replaced by NULL must be dropped from the
226+
* tree.
227+
*/
227228
for (i=0;i<root->nchild;i++)
228229
{
229-
if (root->child[i])
230-
{
231-
root->child[j]=root->child[i];
230+
root->child[j]=dofindsubquery(root->child[i],ex,subs,isfind);
231+
if (root->child[j])
232232
j++;
233-
}
234233
}
235234

236235
root->nchild=j;
237236

237+
/*
238+
* If we have just zero or one remaining child node, simplify out this
239+
* operator node.
240+
*/
238241
if (root->nchild==0)
239242
{
240243
QTNFree(root);
@@ -267,9 +270,6 @@ findsubquery(QTNode *root, QTNode *ex, QTNode *subs, bool *isfind)
267270

268271
root=dofindsubquery(root,ex,subs,&DidFind);
269272

270-
if (!subs&&DidFind)
271-
root=dropvoidsubtree(root);
272-
273273
if (isfind)
274274
*isfind=DidFind;
275275

‎src/test/regress/expected/tsearch.out‎

Lines changed: 15 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -1251,6 +1251,21 @@ SELECT ts_rewrite('5 <-> (6 | 8)', 'SELECT keyword, sample FROM test_tsquery'::t
12511251
'5' <-> '7' | '5' <-> '8'
12521252
(1 row)
12531253

1254+
-- Check empty substitution
1255+
SELECT ts_rewrite(to_tsquery('5 & (6 | 5)'), to_tsquery('5'), to_tsquery(''));
1256+
NOTICE: text-search query doesn't contain lexemes: ""
1257+
ts_rewrite
1258+
------------
1259+
'6'
1260+
(1 row)
1261+
1262+
SELECT ts_rewrite(to_tsquery('!5'), to_tsquery('5'), to_tsquery(''));
1263+
NOTICE: text-search query doesn't contain lexemes: ""
1264+
ts_rewrite
1265+
------------
1266+
1267+
(1 row)
1268+
12541269
SELECT keyword FROM test_tsquery WHERE keyword @> 'new';
12551270
keyword
12561271
----------------

‎src/test/regress/sql/tsearch.sql‎

Lines changed: 3 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -418,6 +418,9 @@ SELECT ts_rewrite('1 & (2 <2> 3)', 'SELECT keyword, sample FROM test_tsquery'::t
418418
SELECT ts_rewrite('5 <-> (1 & (2 <-> 3))','SELECT keyword, sample FROM test_tsquery'::text );
419419
SELECT ts_rewrite('5 <-> (6 | 8)','SELECT keyword, sample FROM test_tsquery'::text );
420420

421+
-- Check empty substitution
422+
SELECT ts_rewrite(to_tsquery('5 & (6 | 5)'), to_tsquery('5'), to_tsquery(''));
423+
SELECT ts_rewrite(to_tsquery('!5'), to_tsquery('5'), to_tsquery(''));
421424

422425
SELECT keywordFROM test_tsqueryWHERE keyword @>'new';
423426
SELECT keywordFROM test_tsqueryWHERE keyword @>'moscow';

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