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Commit4eaea3d

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Introduce TupleHashTableHash() and LookupTupleHashEntryHash().
Expose two new entry points: one for only calculating the hash valueof a tuple, and another for looking up a hash entry when the hashvalue is already known. This will be useful for disk-based HashAggregation to avoid recomputing the hash value for the same tupleafter saving and restoring it from disk.Discussion:https://postgr.es/m/37091115219dd522fd9ed67333ee8ed1b7e09443.camel%40j-davis.com
1 parente6f86f8 commit4eaea3d

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2 files changed

+83
-30
lines changed

2 files changed

+83
-30
lines changed

‎src/backend/executor/execGrouping.c

Lines changed: 78 additions & 30 deletions
Original file line numberDiff line numberDiff line change
@@ -25,8 +25,9 @@
2525
#include"utils/lsyscache.h"
2626
#include"utils/memutils.h"
2727

28-
staticuint32TupleHashTableHash(structtuplehash_hash*tb,constMinimalTupletuple);
2928
staticintTupleHashTableMatch(structtuplehash_hash*tb,constMinimalTupletuple1,constMinimalTupletuple2);
29+
staticTupleHashEntryLookupTupleHashEntry_internal(
30+
TupleHashTablehashtable,TupleTableSlot*slot,bool*isnew,uint32hash);
3031

3132
/*
3233
* Define parameters for tuple hash table code generation. The interface is
@@ -300,10 +301,9 @@ TupleHashEntry
300301
LookupTupleHashEntry(TupleHashTablehashtable,TupleTableSlot*slot,
301302
bool*isnew)
302303
{
303-
TupleHashEntryData*entry;
304-
MemoryContextoldContext;
305-
boolfound;
306-
MinimalTuplekey;
304+
TupleHashEntryentry;
305+
MemoryContextoldContext;
306+
uint32hash;
307307

308308
/* Need to run the hash functions in short-lived context */
309309
oldContext=MemoryContextSwitchTo(hashtable->tempcxt);
@@ -313,32 +313,34 @@ LookupTupleHashEntry(TupleHashTable hashtable, TupleTableSlot *slot,
313313
hashtable->in_hash_funcs=hashtable->tab_hash_funcs;
314314
hashtable->cur_eq_func=hashtable->tab_eq_func;
315315

316-
key=NULL;/* flag to reference inputslot */
316+
hash=TupleHashTableHash(hashtable->hashtab,NULL);
317+
entry=LookupTupleHashEntry_internal(hashtable,slot,isnew,hash);
317318

318-
if (isnew)
319-
{
320-
entry=tuplehash_insert(hashtable->hashtab,key,&found);
319+
MemoryContextSwitchTo(oldContext);
321320

322-
if (found)
323-
{
324-
/* found pre-existing entry */
325-
*isnew= false;
326-
}
327-
else
328-
{
329-
/* created new entry */
330-
*isnew= true;
331-
/* zero caller data */
332-
entry->additional=NULL;
333-
MemoryContextSwitchTo(hashtable->tablecxt);
334-
/* Copy the first tuple into the table context */
335-
entry->firstTuple=ExecCopySlotMinimalTuple(slot);
336-
}
337-
}
338-
else
339-
{
340-
entry=tuplehash_lookup(hashtable->hashtab,key);
341-
}
321+
returnentry;
322+
}
323+
324+
/*
325+
* A variant of LookupTupleHashEntry for callers that have already computed
326+
* the hash value.
327+
*/
328+
TupleHashEntry
329+
LookupTupleHashEntryHash(TupleHashTablehashtable,TupleTableSlot*slot,
330+
bool*isnew,uint32hash)
331+
{
332+
TupleHashEntryentry;
333+
MemoryContextoldContext;
334+
335+
/* Need to run the hash functions in short-lived context */
336+
oldContext=MemoryContextSwitchTo(hashtable->tempcxt);
337+
338+
/* set up data needed by hash and match functions */
339+
hashtable->inputslot=slot;
340+
hashtable->in_hash_funcs=hashtable->tab_hash_funcs;
341+
hashtable->cur_eq_func=hashtable->tab_eq_func;
342+
343+
entry=LookupTupleHashEntry_internal(hashtable,slot,isnew,hash);
342344

343345
MemoryContextSwitchTo(oldContext);
344346

@@ -389,7 +391,7 @@ FindTupleHashEntry(TupleHashTable hashtable, TupleTableSlot *slot,
389391
* Also, the caller must select an appropriate memory context for running
390392
* the hash functions. (dynahash.c doesn't change CurrentMemoryContext.)
391393
*/
392-
staticuint32
394+
uint32
393395
TupleHashTableHash(structtuplehash_hash*tb,constMinimalTupletuple)
394396
{
395397
TupleHashTablehashtable= (TupleHashTable)tb->private_data;
@@ -450,6 +452,52 @@ TupleHashTableHash(struct tuplehash_hash *tb, const MinimalTuple tuple)
450452
returnmurmurhash32(hashkey);
451453
}
452454

455+
/*
456+
* Does the work of LookupTupleHashEntry and LookupTupleHashEntryHash. Useful
457+
* so that we can avoid switching the memory context multiple times for
458+
* LookupTupleHashEntry.
459+
*
460+
* NB: This function may or may not change the memory context. Caller is
461+
* expected to change it back.
462+
*/
463+
staticTupleHashEntry
464+
LookupTupleHashEntry_internal(TupleHashTablehashtable,TupleTableSlot*slot,
465+
bool*isnew,uint32hash)
466+
{
467+
TupleHashEntryData*entry;
468+
boolfound;
469+
MinimalTuplekey;
470+
471+
key=NULL;/* flag to reference inputslot */
472+
473+
if (isnew)
474+
{
475+
entry=tuplehash_insert_hash(hashtable->hashtab,key,hash,&found);
476+
477+
if (found)
478+
{
479+
/* found pre-existing entry */
480+
*isnew= false;
481+
}
482+
else
483+
{
484+
/* created new entry */
485+
*isnew= true;
486+
/* zero caller data */
487+
entry->additional=NULL;
488+
MemoryContextSwitchTo(hashtable->tablecxt);
489+
/* Copy the first tuple into the table context */
490+
entry->firstTuple=ExecCopySlotMinimalTuple(slot);
491+
}
492+
}
493+
else
494+
{
495+
entry=tuplehash_lookup_hash(hashtable->hashtab,key,hash);
496+
}
497+
498+
returnentry;
499+
}
500+
453501
/*
454502
* See whether two tuples (presumably of the same hash value) match
455503
*/

‎src/include/executor/executor.h

Lines changed: 5 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -140,6 +140,11 @@ extern TupleHashTable BuildTupleHashTableExt(PlanState *parent,
140140
externTupleHashEntryLookupTupleHashEntry(TupleHashTablehashtable,
141141
TupleTableSlot*slot,
142142
bool*isnew);
143+
externuint32TupleHashTableHash(structtuplehash_hash*tb,
144+
constMinimalTupletuple);
145+
externTupleHashEntryLookupTupleHashEntryHash(TupleHashTablehashtable,
146+
TupleTableSlot*slot,
147+
bool*isnew,uint32hash);
143148
externTupleHashEntryFindTupleHashEntry(TupleHashTablehashtable,
144149
TupleTableSlot*slot,
145150
ExprState*eqcomp,

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