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Commit0d779d2

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Convert tsginidx.c's GIN indexing logic to fully ternary operation.
Commit 2f2007fbb did this partially, but there were two remainingwarts. checkcondition_gin handled some uncertain cases by settingthe out-of-band recheck flag, some by returning TS_MAYBE, and someby doing both. Meanwhile, TS_execute arbitrarily converted aTS_MAYBE result to TS_YES. Thus, if checkcondition_gin chose toonly return TS_MAYBE, the outcome would be TS_YES with no recheckflag, potentially resulting in wrong query outputs.The case where this'd happen is if there were GIN_MAYBE entriesin the indexscan results passed to gin_tsquery_[tri]consistent,which so far as I can see would only happen if the tidbitmap usedto accumulate indexscan results grew large enough to become lossy.I initially thought of fixing this by ensuring we always set therecheck flag as well as returning TS_MAYBE in uncertain cases.But that errs in the other direction, potentially forcing rechecksof rows that provably match the query (since the recheck flagremains set even if TS_execute later finds that the answer must beTS_YES). Instead, let's get rid of the out-of-band recheck flagaltogether and rely on returning TS_MAYBE. This requires exportinga version of TS_execute that will actually return the full ternaryresult of the evaluation ... but we likely should have done thatto start with.Unfortunately it doesn't seem practical to add a regression test casethat covers this: the amount of data needed to cause the GIN bitmap tobecome lossy results in a longer runtime than I think we want to havein the tests. (I'm wondering about allowing smaller work_mem settingsto ameliorate that, but it'd be a matter for a separate patch.)Per bug #16865 from Dimitri Nüscheler. Back-patch to v13 wherethe faulty commit came in.Discussion:https://postgr.es/m/16865-4ffdc3e682e6d75b@postgresql.org
1 parent80dc07a commit0d779d2

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3 files changed

+44
-28
lines changed

3 files changed

+44
-28
lines changed

‎src/backend/utils/adt/tsginidx.c

Lines changed: 29 additions & 28 deletions
Original file line numberDiff line numberDiff line change
@@ -175,7 +175,6 @@ typedef struct
175175
QueryItem*first_item;
176176
GinTernaryValue*check;
177177
int*map_item_operand;
178-
bool*need_recheck;
179178
}GinChkVal;
180179

181180
/*
@@ -186,33 +185,30 @@ checkcondition_gin(void *checkval, QueryOperand *val, ExecPhraseData *data)
186185
{
187186
GinChkVal*gcv= (GinChkVal*)checkval;
188187
intj;
189-
190-
/*
191-
* if any val requiring a weight is used or caller needs position
192-
* information then set recheck flag
193-
*/
194-
if (val->weight!=0||data!=NULL)
195-
*(gcv->need_recheck)= true;
188+
GinTernaryValueresult;
196189

197190
/* convert item's number to corresponding entry's (operand's) number */
198191
j=gcv->map_item_operand[((QueryItem*)val)-gcv->first_item];
199192

193+
/* determine presence of current entry in indexed value */
194+
result=gcv->check[j];
195+
200196
/*
201-
*return presence of current entry in indexed value; but TRUE becomes
202-
*MAYBE in the presence of a query requiring recheck
197+
*If any val requiring a weight is used or caller needs position
198+
*information then we must recheck, so replace TRUE with MAYBE.
203199
*/
204-
if (gcv->check[j]==GIN_TRUE)
200+
if (result==GIN_TRUE)
205201
{
206202
if (val->weight!=0||data!=NULL)
207-
returnTS_MAYBE;
203+
result=GIN_MAYBE;
208204
}
209205

210206
/*
211207
* We rely on GinTernaryValue and TSTernaryValue using equivalent value
212208
* assignments. We could use a switch statement to map the values if that
213209
* ever stops being true, but it seems unlikely to happen.
214210
*/
215-
return (TSTernaryValue)gcv->check[j];
211+
return (TSTernaryValue)result;
216212
}
217213

218214
Datum
@@ -244,12 +240,23 @@ gin_tsquery_consistent(PG_FUNCTION_ARGS)
244240
"sizes of GinTernaryValue and bool are not equal");
245241
gcv.check= (GinTernaryValue*)check;
246242
gcv.map_item_operand= (int*) (extra_data[0]);
247-
gcv.need_recheck=recheck;
248243

249-
res=TS_execute(GETQUERY(query),
250-
&gcv,
251-
TS_EXEC_PHRASE_NO_POS,
252-
checkcondition_gin);
244+
switch (TS_execute_ternary(GETQUERY(query),
245+
&gcv,
246+
TS_EXEC_PHRASE_NO_POS,
247+
checkcondition_gin))
248+
{
249+
caseTS_NO:
250+
res= false;
251+
break;
252+
caseTS_YES:
253+
res= true;
254+
break;
255+
caseTS_MAYBE:
256+
res= true;
257+
*recheck= true;
258+
break;
259+
}
253260
}
254261

255262
PG_RETURN_BOOL(res);
@@ -266,10 +273,6 @@ gin_tsquery_triconsistent(PG_FUNCTION_ARGS)
266273
/* int32nkeys = PG_GETARG_INT32(3); */
267274
Pointer*extra_data= (Pointer*)PG_GETARG_POINTER(4);
268275
GinTernaryValueres=GIN_FALSE;
269-
boolrecheck;
270-
271-
/* Initially assume query doesn't require recheck */
272-
recheck= false;
273276

274277
if (query->size>0)
275278
{
@@ -282,13 +285,11 @@ gin_tsquery_triconsistent(PG_FUNCTION_ARGS)
282285
gcv.first_item=GETQUERY(query);
283286
gcv.check=check;
284287
gcv.map_item_operand= (int*) (extra_data[0]);
285-
gcv.need_recheck=&recheck;
286288

287-
if (TS_execute(GETQUERY(query),
288-
&gcv,
289-
TS_EXEC_PHRASE_NO_POS,
290-
checkcondition_gin))
291-
res=recheck ?GIN_MAYBE :GIN_TRUE;
289+
res=TS_execute_ternary(GETQUERY(query),
290+
&gcv,
291+
TS_EXEC_PHRASE_NO_POS,
292+
checkcondition_gin);
292293
}
293294

294295
PG_RETURN_GIN_TERNARY_VALUE(res);

‎src/backend/utils/adt/tsvector_op.c

Lines changed: 12 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -1854,6 +1854,18 @@ TS_execute(QueryItem *curitem, void *arg, uint32 flags,
18541854
returnTS_execute_recurse(curitem,arg,flags,chkcond)!=TS_NO;
18551855
}
18561856

1857+
/*
1858+
* Evaluate tsquery boolean expression.
1859+
*
1860+
* This is the same as TS_execute except that TS_MAYBE is returned as-is.
1861+
*/
1862+
TSTernaryValue
1863+
TS_execute_ternary(QueryItem*curitem,void*arg,uint32flags,
1864+
TSExecuteCallbackchkcond)
1865+
{
1866+
returnTS_execute_recurse(curitem,arg,flags,chkcond);
1867+
}
1868+
18571869
/*
18581870
* TS_execute recursion for operators above any phrase operator. Here we do
18591871
* not need to worry about lexeme positions. As soon as we hit an OP_PHRASE

‎src/include/tsearch/ts_utils.h

Lines changed: 3 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -199,6 +199,9 @@ typedef TSTernaryValue (*TSExecuteCallback) (void *arg, QueryOperand *val,
199199

200200
externboolTS_execute(QueryItem*curitem,void*arg,uint32flags,
201201
TSExecuteCallbackchkcond);
202+
externTSTernaryValueTS_execute_ternary(QueryItem*curitem,void*arg,
203+
uint32flags,
204+
TSExecuteCallbackchkcond);
202205
externbooltsquery_requires_match(QueryItem*curitem);
203206

204207
/*

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