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Commit299d171

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Install defenses against overflow in BuildTupleHashTable().
The planner can sometimes compute very large values for numGroups, and incases where we have no alternative to building a hashtable, such a valuewill get fed directly to BuildTupleHashTable as its nbuckets parameter.There were two ways in which that could go bad. First, BuildTupleHashTabledeclared the parameter as "int" but most callers were passing "long"s,so on 64-bit machines undetected overflow could occur leading to a bogusnegative value. The obvious fix for that is to change the parameter to"long", which is what I've done in HEAD. In the back branches that seems abit risky, though, since third-party code might be calling this function.So for them, just put in a kluge to treat negative inputs as INT_MAX.Second, hash_create can go nuts with extremely large requested table sizes(notably, my_log2 becomes an infinite loop for inputs larger thanLONG_MAX/2). What seems most appropriate to avoid that is to bound theinitial table size request to work_mem.This fixes bug #6035 reported by Daniel Schreiber. Although the reportedcase only occurs back to 8.4 since it involves WITH RECURSIVE, I thinkit's a good idea to install the defenses in all supported branches.
1 parenta9b6519 commit299d171

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3 files changed

+9
-5
lines changed

3 files changed

+9
-5
lines changed

‎src/backend/executor/execGrouping.c

Lines changed: 6 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -19,6 +19,7 @@
1919
#include"postgres.h"
2020

2121
#include"executor/executor.h"
22+
#include"miscadmin.h"
2223
#include"parser/parse_oper.h"
2324
#include"utils/lsyscache.h"
2425
#include"utils/memutils.h"
@@ -276,7 +277,7 @@ TupleHashTable
276277
BuildTupleHashTable(intnumCols,AttrNumber*keyColIdx,
277278
FmgrInfo*eqfunctions,
278279
FmgrInfo*hashfunctions,
279-
intnbuckets,Sizeentrysize,
280+
longnbuckets,Sizeentrysize,
280281
MemoryContexttablecxt,MemoryContexttempcxt)
281282
{
282283
TupleHashTablehashtable;
@@ -285,6 +286,9 @@ BuildTupleHashTable(int numCols, AttrNumber *keyColIdx,
285286
Assert(nbuckets>0);
286287
Assert(entrysize >=sizeof(TupleHashEntryData));
287288

289+
/* Limit initial table size request to not more than work_mem */
290+
nbuckets=Min(nbuckets, (long) ((work_mem*1024L) /entrysize));
291+
288292
hashtable= (TupleHashTable)MemoryContextAlloc(tablecxt,
289293
sizeof(TupleHashTableData));
290294

@@ -306,7 +310,7 @@ BuildTupleHashTable(int numCols, AttrNumber *keyColIdx,
306310
hash_ctl.hash=TupleHashTableHash;
307311
hash_ctl.match=TupleHashTableMatch;
308312
hash_ctl.hcxt=tablecxt;
309-
hashtable->hashtab=hash_create("TupleHashTable",(long)nbuckets,
313+
hashtable->hashtab=hash_create("TupleHashTable",nbuckets,
310314
&hash_ctl,
311315
HASH_ELEM |HASH_FUNCTION |HASH_COMPARE |HASH_CONTEXT);
312316

‎src/backend/executor/nodeSubplan.c

Lines changed: 2 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -432,7 +432,7 @@ buildSubPlanHash(SubPlanState *node, ExprContext *econtext)
432432
intncols=list_length(subplan->paramIds);
433433
ExprContext*innerecontext=node->innerecontext;
434434
MemoryContextoldcontext;
435-
intnbuckets;
435+
longnbuckets;
436436
TupleTableSlot*slot;
437437

438438
Assert(subplan->subLinkType==ANY_SUBLINK);
@@ -458,7 +458,7 @@ buildSubPlanHash(SubPlanState *node, ExprContext *econtext)
458458
node->havehashrows= false;
459459
node->havenullrows= false;
460460

461-
nbuckets= (int)ceil(planstate->plan->plan_rows);
461+
nbuckets= (long)Min(planstate->plan->plan_rows, (double)LONG_MAX);
462462
if (nbuckets<1)
463463
nbuckets=1;
464464

‎src/include/executor/executor.h

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -131,7 +131,7 @@ extern void execTuplesHashPrepare(int numCols,
131131
externTupleHashTableBuildTupleHashTable(intnumCols,AttrNumber*keyColIdx,
132132
FmgrInfo*eqfunctions,
133133
FmgrInfo*hashfunctions,
134-
intnbuckets,Sizeentrysize,
134+
longnbuckets,Sizeentrysize,
135135
MemoryContexttablecxt,
136136
MemoryContexttempcxt);
137137
externTupleHashEntryLookupTupleHashEntry(TupleHashTablehashtable,

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