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Commitde57004

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Fix some oversights in commit2455ab4.
The idea was to generate all the junk in a destroyable subcontext ratherthan leaking it in the caller's context, but partition_bounds_create wasstill being called in the caller's context, allowing plenty of scope forleakage. Also, get_rel_relkind() was still being called in the rel'srd_pdcxt, creating a risk of session-lifespan memory wastage.Simplify the logic a bit while at it. Also, reduce rd_pdcxt toALLOCSET_SMALL_SIZES, since it seems likely to not usually be big.Probably something like this needs to be back-patched into v11,but for now let's get some buildfarm testing on this.Discussion:https://postgr.es/m/15943.1552601288@sss.pgh.pa.us
1 parent61dc407 commitde57004

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+33
-39
lines changed

1 file changed

+33
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lines changed

‎src/backend/partitioning/partdesc.c

Lines changed: 33 additions & 39 deletions
Original file line numberDiff line numberDiff line change
@@ -67,8 +67,8 @@ RelationBuildPartitionDesc(Relation rel)
6767
nparts;
6868
PartitionKeykey=RelationGetPartitionKey(rel);
6969
MemoryContextoldcxt;
70+
MemoryContextrbcontext;
7071
int*mapping;
71-
MemoryContextrbcontext=NULL;
7272

7373
/*
7474
* While building the partition descriptor, we create various temporary
@@ -187,56 +187,50 @@ RelationBuildPartitionDesc(Relation rel)
187187
/* Now build the actual relcache partition descriptor */
188188
rel->rd_pdcxt=AllocSetContextCreate(CacheMemoryContext,
189189
"partition descriptor",
190-
ALLOCSET_DEFAULT_SIZES);
190+
ALLOCSET_SMALL_SIZES);
191191
MemoryContextCopyAndSetIdentifier(rel->rd_pdcxt,
192192
RelationGetRelationName(rel));
193193

194-
MemoryContextSwitchTo(rel->rd_pdcxt);
195-
partdesc= (PartitionDescData*)palloc0(sizeof(PartitionDescData));
194+
partdesc= (PartitionDescData*)
195+
MemoryContextAllocZero(rel->rd_pdcxt,sizeof(PartitionDescData));
196196
partdesc->nparts=nparts;
197-
/* oids and boundinfo are allocated below. */
198-
199-
MemoryContextSwitchTo(oldcxt);
200-
201-
if (nparts==0)
197+
/* If there are no partitions, the rest of the partdesc can stay zero */
198+
if (nparts>0)
202199
{
203-
/*We can exit early in this case. */
204-
rel->rd_partdesc=partdesc;
200+
/*Create PartitionBoundInfo, using the temporary context. */
201+
boundinfo=partition_bounds_create(boundspecs,nparts,key,&mapping);
205202

206-
/* Blow away the temporary context. */
207-
MemoryContextDelete(rbcontext);
208-
return;
209-
}
203+
/* Now copy all info into relcache's partdesc. */
204+
MemoryContextSwitchTo(rel->rd_pdcxt);
205+
partdesc->boundinfo=partition_bounds_copy(boundinfo,key);
206+
partdesc->oids= (Oid*)palloc(nparts*sizeof(Oid));
207+
partdesc->is_leaf= (bool*)palloc(nparts*sizeof(bool));
210208

211-
/* First create PartitionBoundInfo */
212-
boundinfo=partition_bounds_create(boundspecs,nparts,key,&mapping);
213-
214-
/* Now copy boundinfo and oids into partdesc. */
215-
oldcxt=MemoryContextSwitchTo(rel->rd_pdcxt);
216-
partdesc->boundinfo=partition_bounds_copy(boundinfo,key);
217-
partdesc->oids= (Oid*)palloc(partdesc->nparts*sizeof(Oid));
218-
partdesc->is_leaf= (bool*)palloc(partdesc->nparts*sizeof(bool));
219-
220-
/*
221-
* Now assign OIDs from the original array into mapped indexes of the
222-
* result array. The order of OIDs in the former is defined by the
223-
* catalog scan that retrieved them, whereas that in the latter is defined
224-
* by canonicalized representation of the partition bounds.
225-
*/
226-
for (i=0;i<partdesc->nparts;i++)
227-
{
228-
intindex=mapping[i];
209+
/*
210+
* Assign OIDs from the original array into mapped indexes of the
211+
* result array. The order of OIDs in the former is defined by the
212+
* catalog scan that retrieved them, whereas that in the latter is
213+
* defined by canonicalized representation of the partition bounds.
214+
*
215+
* Also record leaf-ness of each partition. For this we use
216+
* get_rel_relkind() which may leak memory, so be sure to run it in
217+
* the temporary context.
218+
*/
219+
MemoryContextSwitchTo(rbcontext);
220+
for (i=0;i<nparts;i++)
221+
{
222+
intindex=mapping[i];
229223

230-
partdesc->oids[index]=oids[i];
231-
/* Record if the partition is a leaf partition */
232-
partdesc->is_leaf[index]=
233-
(get_rel_relkind(oids[i])!=RELKIND_PARTITIONED_TABLE);
224+
partdesc->oids[index]=oids[i];
225+
partdesc->is_leaf[index]=
226+
(get_rel_relkind(oids[i])!=RELKIND_PARTITIONED_TABLE);
227+
}
234228
}
235-
MemoryContextSwitchTo(oldcxt);
236229

237230
rel->rd_partdesc=partdesc;
238231

239-
/* Blow away the temporary context. */
232+
/* Return to caller's context, and blow away the temporary context. */
233+
MemoryContextSwitchTo(oldcxt);
240234
MemoryContextDelete(rbcontext);
241235
}
242236

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