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Redesign get_attstatsslot()/free_attstatsslot() for more safety and speed.
The mess cleaned up in commit da07596 is clear evidence that it's a bug hazard to expect the caller of get_attstatsslot()/free_attstatsslot() to provide the correct type OID for the array elements in the slot. Moreover, we weren't even getting any performance benefit from that, since get_attstatsslot() was extracting the real type OID from the array anyway. So we ought to get rid of that requirement; indeed, it would make more sense for get_attstatsslot() to pass back the type OID it found, in case the caller isn't sure what to expect, which is likely in binary- compatible-operator cases. Another problem with the current implementation is that if the stats array element type is pass-by-reference, we incur a palloc/memcpy/pfree cycle for each element. That seemed acceptable when the code was written because we were targeting O(10) array sizes --- but these days, stats arrays are almost always bigger than that, sometimes much bigger. We can save a significant number of cycles by doing one palloc/memcpy/pfree of the whole array. Indeed, in the now-probably-common case where the array is toasted, that happens anyway so this method is basically free. (Note: although the catcache code will inline any out-of-line toasted values, it doesn't decompress them. At the other end of the size range, it doesn't expand short-header datums either. In either case, DatumGetArrayTypeP would have to make a copy. We do end up using an extra array copy step if the element type is pass-by-value and the array length is neither small enough for a short header nor large enough to have suffered compression. But that seems like a very acceptable price for winning in pass-by-ref cases.) Hence, redesign to take these insights into account. While at it, convert to an API in which we fill a struct rather than passing a bunch of pointers to individual output arguments. That will make it less painful if we ever want further expansion of what get_attstatsslot can pass back. It's certainly arguable that this is new development and not something to push post-feature-freeze. However, I view it as primarily bug-proofing and therefore something that's better to have sooner not later. Since we aren't quite at beta phase yet, let's put it in. Discussion: https://postgr.es/m/16364.1494520862@sss.pgh.pa.us
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10 files changed

+436
-601
lines changed

10 files changed

+436
-601
lines changed

‎contrib/intarray/_int_selfuncs.c

Lines changed: 15 additions & 16 deletions
Original file line numberDiff line numberDiff line change
@@ -136,11 +136,7 @@ _int_matchsel(PG_FUNCTION_ARGS)
136136
int nmcelems = 0;
137137
float4 minfreq = 0.0;
138138
float4 nullfrac = 0.0;
139-
Form_pg_statistic stats;
140-
Datum *values = NULL;
141-
int nvalues = 0;
142-
float4 *numbers = NULL;
143-
int nnumbers = 0;
139+
AttStatsSlot sslot;
144140

145141
/*
146142
* If expression is not "variable @@ something" or "something @@ variable"
@@ -193,36 +189,39 @@ _int_matchsel(PG_FUNCTION_ARGS)
193189
*/
194190
if (HeapTupleIsValid(vardata.statsTuple))
195191
{
192+
Form_pg_statistic stats;
193+
196194
stats = (Form_pg_statistic) GETSTRUCT(vardata.statsTuple);
197195
nullfrac = stats->stanullfrac;
198196

199197
/*
200198
* For an int4 array, the default array type analyze function will
201199
* collect a Most Common Elements list, which is an array of int4s.
202200
*/
203-
if (get_attstatsslot(vardata.statsTuple,
204-
INT4OID, -1,
201+
if (get_attstatsslot(&sslot, vardata.statsTuple,
205202
STATISTIC_KIND_MCELEM, InvalidOid,
206-
NULL,
207-
&values, &nvalues,
208-
&numbers, &nnumbers))
203+
ATTSTATSSLOT_VALUES | ATTSTATSSLOT_NUMBERS))
209204
{
205+
Assert(sslot.valuetype == INT4OID);
206+
210207
/*
211208
* There should be three more Numbers than Values, because the
212209
* last three (for intarray) cells are taken for minimal, maximal
213210
* and nulls frequency. Punt if not.
214211
*/
215-
if (nnumbers == nvalues + 3)
212+
if (sslot.nnumbers == sslot.nvalues + 3)
216213
{
217214
/* Grab the lowest frequency. */
218-
minfreq = numbers[nnumbers - (nnumbers - nvalues)];
215+
minfreq = sslot.numbers[sslot.nnumbers - (sslot.nnumbers - sslot.nvalues)];
219216

220-
mcelems = values;
221-
mcefreqs = numbers;
222-
nmcelems = nvalues;
217+
mcelems = sslot.values;
218+
mcefreqs = sslot.numbers;
219+
nmcelems = sslot.nvalues;
223220
}
224221
}
225222
}
223+
else
224+
memset(&sslot, 0, sizeof(sslot));
226225

227226
/* Process the logical expression in the query, using the stats */
228227
selec = int_query_opr_selec(GETQUERY(query) + query->size - 1,
@@ -231,7 +230,7 @@ _int_matchsel(PG_FUNCTION_ARGS)
231230
/* MCE stats count only non-null rows, so adjust for null rows. */
232231
selec *= (1.0 - nullfrac);
233232

234-
free_attstatsslot(INT4OID, values, nvalues, numbers, nnumbers);
233+
free_attstatsslot(&sslot);
235234
ReleaseVariableStats(vardata);
236235

237236
CLAMP_PROBABILITY(selec);

‎src/backend/executor/nodeHash.c

Lines changed: 9 additions & 16 deletions
Original file line numberDiff line numberDiff line change
@@ -1283,10 +1283,7 @@ static void
12831283
ExecHashBuildSkewHash(HashJoinTable hashtable, Hash *node, int mcvsToUse)
12841284
{
12851285
HeapTupleData *statsTuple;
1286-
Datum *values;
1287-
int nvalues;
1288-
float4 *numbers;
1289-
int nnumbers;
1286+
AttStatsSlot sslot;
12901287

12911288
/* Do nothing if planner didn't identify the outer relation's join key */
12921289
if (!OidIsValid(node->skewTable))
@@ -1305,19 +1302,17 @@ ExecHashBuildSkewHash(HashJoinTable hashtable, Hash *node, int mcvsToUse)
13051302
if (!HeapTupleIsValid(statsTuple))
13061303
return;
13071304

1308-
if (get_attstatsslot(statsTuple, node->skewColType, node->skewColTypmod,
1305+
if (get_attstatsslot(&sslot, statsTuple,
13091306
STATISTIC_KIND_MCV, InvalidOid,
1310-
NULL,
1311-
&values, &nvalues,
1312-
&numbers, &nnumbers))
1307+
ATTSTATSSLOT_VALUES | ATTSTATSSLOT_NUMBERS))
13131308
{
13141309
double frac;
13151310
int nbuckets;
13161311
FmgrInfo *hashfunctions;
13171312
int i;
13181313

1319-
if (mcvsToUse > nvalues)
1320-
mcvsToUse = nvalues;
1314+
if (mcvsToUse > sslot.nvalues)
1315+
mcvsToUse = sslot.nvalues;
13211316

13221317
/*
13231318
* Calculate the expected fraction of outer relation that will
@@ -1326,11 +1321,10 @@ ExecHashBuildSkewHash(HashJoinTable hashtable, Hash *node, int mcvsToUse)
13261321
*/
13271322
frac = 0;
13281323
for (i = 0; i < mcvsToUse; i++)
1329-
frac += numbers[i];
1324+
frac += sslot.numbers[i];
13301325
if (frac < SKEW_MIN_OUTER_FRACTION)
13311326
{
1332-
free_attstatsslot(node->skewColType,
1333-
values, nvalues, numbers, nnumbers);
1327+
free_attstatsslot(&sslot);
13341328
ReleaseSysCache(statsTuple);
13351329
return;
13361330
}
@@ -1392,7 +1386,7 @@ ExecHashBuildSkewHash(HashJoinTable hashtable, Hash *node, int mcvsToUse)
13921386
int bucket;
13931387

13941388
hashvalue = DatumGetUInt32(FunctionCall1(&hashfunctions[0],
1395-
values[i]));
1389+
sslot.values[i]));
13961390

13971391
/*
13981392
* While we have not hit a hole in the hashtable and have not hit
@@ -1426,8 +1420,7 @@ ExecHashBuildSkewHash(HashJoinTable hashtable, Hash *node, int mcvsToUse)
14261420
hashtable->spacePeak = hashtable->spaceUsed;
14271421
}
14281422

1429-
free_attstatsslot(node->skewColType,
1430-
values, nvalues, numbers, nnumbers);
1423+
free_attstatsslot(&sslot);
14311424
}
14321425

14331426
ReleaseSysCache(statsTuple);

‎src/backend/tsearch/ts_selfuncs.c

Lines changed: 6 additions & 12 deletions
Original file line numberDiff line numberDiff line change
@@ -163,28 +163,22 @@ tsquerysel(VariableStatData *vardata, Datum constval)
163163
if (HeapTupleIsValid(vardata->statsTuple))
164164
{
165165
Form_pg_statistic stats;
166-
Datum *values;
167-
int nvalues;
168-
float4 *numbers;
169-
int nnumbers;
166+
AttStatsSlot sslot;
170167

171168
stats = (Form_pg_statistic) GETSTRUCT(vardata->statsTuple);
172169

173170
/* MCELEM will be an array of TEXT elements for a tsvector column */
174-
if (get_attstatsslot(vardata->statsTuple,
175-
TEXTOID, -1,
171+
if (get_attstatsslot(&sslot, vardata->statsTuple,
176172
STATISTIC_KIND_MCELEM, InvalidOid,
177-
NULL,
178-
&values, &nvalues,
179-
&numbers, &nnumbers))
173+
ATTSTATSSLOT_VALUES | ATTSTATSSLOT_NUMBERS))
180174
{
181175
/*
182176
* There is a most-common-elements slot for the tsvector Var, so
183177
* use that.
184178
*/
185-
selec = mcelem_tsquery_selec(query, values, nvalues,
186-
numbers, nnumbers);
187-
free_attstatsslot(TEXTOID, values, nvalues, numbers, nnumbers);
179+
selec = mcelem_tsquery_selec(query, sslot.values, sslot.nvalues,
180+
sslot.numbers, sslot.nnumbers);
181+
free_attstatsslot(&sslot);
188182
}
189183
else
190184
{

‎src/backend/utils/adt/array_selfuncs.c

Lines changed: 31 additions & 54 deletions
Original file line numberDiff line numberDiff line change
@@ -137,58 +137,49 @@ scalararraysel_containment(PlannerInfo *root,
137137
statistic_proc_security_check(&vardata, cmpfunc->fn_oid))
138138
{
139139
Form_pg_statistic stats;
140-
Datum *values;
141-
int nvalues;
142-
float4 *numbers;
143-
int nnumbers;
144-
float4 *hist;
145-
int nhist;
140+
AttStatsSlot sslot;
141+
AttStatsSlot hslot;
146142

147143
stats = (Form_pg_statistic) GETSTRUCT(vardata.statsTuple);
148144

149145
/* MCELEM will be an array of same type as element */
150-
if (get_attstatsslot(vardata.statsTuple,
151-
elemtype, vardata.atttypmod,
146+
if (get_attstatsslot(&sslot, vardata.statsTuple,
152147
STATISTIC_KIND_MCELEM, InvalidOid,
153-
NULL,
154-
&values, &nvalues,
155-
&numbers, &nnumbers))
148+
ATTSTATSSLOT_VALUES | ATTSTATSSLOT_NUMBERS))
156149
{
157150
/* For ALL case, also get histogram of distinct-element counts */
158151
if (useOr ||
159-
!get_attstatsslot(vardata.statsTuple,
160-
elemtype, vardata.atttypmod,
152+
!get_attstatsslot(&hslot, vardata.statsTuple,
161153
STATISTIC_KIND_DECHIST, InvalidOid,
162-
NULL,
163-
NULL, NULL,
164-
&hist, &nhist))
165-
{
166-
hist = NULL;
167-
nhist = 0;
168-
}
154+
ATTSTATSSLOT_NUMBERS))
155+
memset(&hslot, 0, sizeof(hslot));
169156

170157
/*
171158
* For = ANY, estimate as var @> ARRAY[const].
172159
*
173160
* For = ALL, estimate as var <@ ARRAY[const].
174161
*/
175162
if (useOr)
176-
selec = mcelem_array_contain_overlap_selec(values, nvalues,
177-
numbers, nnumbers,
163+
selec = mcelem_array_contain_overlap_selec(sslot.values,
164+
sslot.nvalues,
165+
sslot.numbers,
166+
sslot.nnumbers,
178167
&constval, 1,
179168
OID_ARRAY_CONTAINS_OP,
180169
cmpfunc);
181170
else
182-
selec = mcelem_array_contained_selec(values, nvalues,
183-
numbers, nnumbers,
171+
selec = mcelem_array_contained_selec(sslot.values,
172+
sslot.nvalues,
173+
sslot.numbers,
174+
sslot.nnumbers,
184175
&constval, 1,
185-
hist, nhist,
176+
hslot.numbers,
177+
hslot.nnumbers,
186178
OID_ARRAY_CONTAINED_OP,
187179
cmpfunc);
188180

189-
if (hist)
190-
free_attstatsslot(elemtype, NULL, 0, hist, nhist);
191-
free_attstatsslot(elemtype, values, nvalues, numbers, nnumbers);
181+
free_attstatsslot(&hslot);
182+
free_attstatsslot(&sslot);
192183
}
193184
else
194185
{
@@ -369,49 +360,35 @@ calc_arraycontsel(VariableStatData *vardata, Datum constval,
369360
statistic_proc_security_check(vardata, cmpfunc->fn_oid))
370361
{
371362
Form_pg_statistic stats;
372-
Datum *values;
373-
int nvalues;
374-
float4 *numbers;
375-
int nnumbers;
376-
float4 *hist;
377-
int nhist;
363+
AttStatsSlot sslot;
364+
AttStatsSlot hslot;
378365

379366
stats = (Form_pg_statistic) GETSTRUCT(vardata->statsTuple);
380367

381368
/* MCELEM will be an array of same type as column */
382-
if (get_attstatsslot(vardata->statsTuple,
383-
elemtype, vardata->atttypmod,
369+
if (get_attstatsslot(&sslot, vardata->statsTuple,
384370
STATISTIC_KIND_MCELEM, InvalidOid,
385-
NULL,
386-
&values, &nvalues,
387-
&numbers, &nnumbers))
371+
ATTSTATSSLOT_VALUES | ATTSTATSSLOT_NUMBERS))
388372
{
389373
/*
390374
* For "array <@ const" case we also need histogram of distinct
391375
* element counts.
392376
*/
393377
if (operator != OID_ARRAY_CONTAINED_OP ||
394-
!get_attstatsslot(vardata->statsTuple,
395-
elemtype, vardata->atttypmod,
378+
!get_attstatsslot(&hslot, vardata->statsTuple,
396379
STATISTIC_KIND_DECHIST, InvalidOid,
397-
NULL,
398-
NULL, NULL,
399-
&hist, &nhist))
400-
{
401-
hist = NULL;
402-
nhist = 0;
403-
}
380+
ATTSTATSSLOT_NUMBERS))
381+
memset(&hslot, 0, sizeof(hslot));
404382

405383
/* Use the most-common-elements slot for the array Var. */
406384
selec = mcelem_array_selec(array, typentry,
407-
values, nvalues,
408-
numbers, nnumbers,
409-
hist, nhist,
385+
sslot.values, sslot.nvalues,
386+
sslot.numbers, sslot.nnumbers,
387+
hslot.numbers, hslot.nnumbers,
410388
operator, cmpfunc);
411389

412-
if (hist)
413-
free_attstatsslot(elemtype, NULL, 0, hist, nhist);
414-
free_attstatsslot(elemtype, values, nvalues, numbers, nnumbers);
390+
free_attstatsslot(&hslot);
391+
free_attstatsslot(&sslot);
415392
}
416393
else
417394
{

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