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Minor refactor of nodeAgg.c. 

* Separate calculation of hash value from the lookup.
  * Split build_hash_table() into two functions.
  * Change lookup_hash_entry() to return AggStatePerGroup. That's all
    the caller needed, anyway.

These changes are to support the upcoming Disk-based Hash Aggregation
work.

Discussion: https://postgr.es/m/31f5ab871a3ad5a1a91a7a797651f20e77ac7ce3.camel%40j-davis.com
This commit is contained in:
Jeff Davis 2020-02-19 10:15:16 -08:00
parent 8021985d79
commit 5b618e1f48
1 changed files with 89 additions and 51 deletions
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140
src/backend/executor/nodeAgg.c
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@ -263,6 +263,7 @@ static void finalize_partialaggregate(AggState *aggstate,
AggStatePerAgg peragg,
AggStatePerGroup pergroupstate,
Datum *resultVal, bool *resultIsNull);
static void prepare_hash_slot(AggState *aggstate);
static void prepare_projection_slot(AggState *aggstate,
TupleTableSlot *slot,
int currentSet);
@ -272,8 +273,9 @@ static void finalize_aggregates(AggState *aggstate,
static TupleTableSlot *project_aggregates(AggState *aggstate);
static Bitmapset *find_unaggregated_cols(AggState *aggstate);
static bool find_unaggregated_cols_walker(Node *node, Bitmapset **colnos);
static void build_hash_table(AggState *aggstate);
static TupleHashEntryData *lookup_hash_entry(AggState *aggstate);
static void build_hash_tables(AggState *aggstate);
static void build_hash_table(AggState *aggstate, int setno, long nbuckets);
static AggStatePerGroup lookup_hash_entry(AggState *aggstate, uint32 hash);
static void lookup_hash_entries(AggState *aggstate);
static TupleTableSlot *agg_retrieve_direct(AggState *aggstate);
static void agg_fill_hash_table(AggState *aggstate);
@ -1035,6 +1037,32 @@ finalize_partialaggregate(AggState *aggstate,
MemoryContextSwitchTo(oldContext);
}
/*
* Extract the attributes that make up the grouping key into the
* hashslot. This is necessary to compute the hash or perform a lookup.
*/
static void
prepare_hash_slot(AggState *aggstate)
{
TupleTableSlot *inputslot = aggstate->tmpcontext->ecxt_outertuple;
AggStatePerHash perhash = &aggstate->perhash[aggstate->current_set];
TupleTableSlot *hashslot = perhash->hashslot;
int i;
/* transfer just the needed columns into hashslot */
slot_getsomeattrs(inputslot, perhash->largestGrpColIdx);
ExecClearTuple(hashslot);
for (i = 0; i < perhash->numhashGrpCols; i++)
{
int varNumber = perhash->hashGrpColIdxInput[i] - 1;
hashslot->tts_values[i] = inputslot->tts_values[varNumber];
hashslot->tts_isnull[i] = inputslot->tts_isnull[varNumber];
}
ExecStoreVirtualTuple(hashslot);
}
/*
* Prepare to finalize and project based on the specified representative tuple
* slot and grouping set.
@ -1249,41 +1277,59 @@ find_unaggregated_cols_walker(Node *node, Bitmapset **colnos)
* they are all reset at the same time).
*/
static void
build_hash_table(AggState *aggstate)
build_hash_tables(AggState *aggstate)
{
MemoryContext tmpmem = aggstate->tmpcontext->ecxt_per_tuple_memory;
Size additionalsize;
int i;
int setno;
Assert(aggstate->aggstrategy == AGG_HASHED || aggstate->aggstrategy == AGG_MIXED);
additionalsize = aggstate->numtrans * sizeof(AggStatePerGroupData);
for (i = 0; i < aggstate->num_hashes; ++i)
for (setno = 0; setno < aggstate->num_hashes; ++setno)
{
AggStatePerHash perhash = &aggstate->perhash[i];
AggStatePerHash perhash = &aggstate->perhash[setno];
Assert(perhash->aggnode->numGroups > 0);
if (perhash->hashtable)
ResetTupleHashTable(perhash->hashtable);
else
perhash->hashtable = BuildTupleHashTableExt(&aggstate->ss.ps,
perhash->hashslot->tts_tupleDescriptor,
perhash->numCols,
perhash->hashGrpColIdxHash,
perhash->eqfuncoids,
perhash->hashfunctions,
perhash->aggnode->grpCollations,
perhash->aggnode->numGroups,
additionalsize,
aggstate->ss.ps.state->es_query_cxt,
aggstate->hashcontext->ecxt_per_tuple_memory,
tmpmem,
DO_AGGSPLIT_SKIPFINAL(aggstate->aggsplit));
build_hash_table(aggstate, setno, perhash->aggnode->numGroups);
}
}
/*
* Build a single hashtable for this grouping set.
*/
static void
build_hash_table(AggState *aggstate, int setno, long nbuckets)
{
AggStatePerHash perhash = &aggstate->perhash[setno];
MemoryContext metacxt = aggstate->ss.ps.state->es_query_cxt;
MemoryContext hashcxt = aggstate->hashcontext->ecxt_per_tuple_memory;
MemoryContext tmpcxt = aggstate->tmpcontext->ecxt_per_tuple_memory;
Size additionalsize;
Assert(aggstate->aggstrategy == AGG_HASHED ||
aggstate->aggstrategy == AGG_MIXED);
/*
* Used to make sure initial hash table allocation does not exceed
* work_mem. Note that the estimate does not include space for
* pass-by-reference transition data values, nor for the representative
* tuple of each group.
*/
additionalsize = aggstate->numtrans * sizeof(AggStatePerGroupData);
perhash->hashtable = BuildTupleHashTableExt(
&aggstate->ss.ps,
perhash->hashslot->tts_tupleDescriptor,
perhash->numCols,
perhash->hashGrpColIdxHash,
perhash->eqfuncoids,
perhash->hashfunctions,
perhash->aggnode->grpCollations,
nbuckets,
additionalsize,
metacxt,
hashcxt,
tmpcxt,
DO_AGGSPLIT_SKIPFINAL(aggstate->aggsplit));
}
/*
* Compute columns that actually need to be stored in hashtable entries. The
* incoming tuples from the child plan node will contain grouping columns,
@ -1441,33 +1487,20 @@ hash_agg_entry_size(int numAggs, Size tupleWidth, Size transitionSpace)
* set (which the caller must have selected - note that initialize_aggregate
* depends on this).
*
* When called, CurrentMemoryContext should be the per-query context.
* When called, CurrentMemoryContext should be the per-query context. The
* already-calculated hash value for the tuple must be specified.
*/
static TupleHashEntryData *
lookup_hash_entry(AggState *aggstate)
static AggStatePerGroup
lookup_hash_entry(AggState *aggstate, uint32 hash)
{
TupleTableSlot *inputslot = aggstate->tmpcontext->ecxt_outertuple;
AggStatePerHash perhash = &aggstate->perhash[aggstate->current_set];
TupleTableSlot *hashslot = perhash->hashslot;
TupleHashEntryData *entry;
bool isnew;
int i;
/* transfer just the needed columns into hashslot */
slot_getsomeattrs(inputslot, perhash->largestGrpColIdx);
ExecClearTuple(hashslot);
for (i = 0; i < perhash->numhashGrpCols; i++)
{
int varNumber = perhash->hashGrpColIdxInput[i] - 1;
hashslot->tts_values[i] = inputslot->tts_values[varNumber];
hashslot->tts_isnull[i] = inputslot->tts_isnull[varNumber];
}
ExecStoreVirtualTuple(hashslot);
/* find or create the hashtable entry using the filtered tuple */
entry = LookupTupleHashEntry(perhash->hashtable, hashslot, &isnew);
entry = LookupTupleHashEntryHash(perhash->hashtable, hashslot, &isnew,
hash);
if (isnew)
{
@ -1492,7 +1525,7 @@ lookup_hash_entry(AggState *aggstate)
}
}
return entry;
return entry->additional;
}
/*
@ -1510,8 +1543,13 @@ lookup_hash_entries(AggState *aggstate)
for (setno = 0; setno < numHashes; setno++)
{
AggStatePerHash perhash = &aggstate->perhash[setno];
uint32 hash;
select_current_set(aggstate, setno, true);
pergroup[setno] = lookup_hash_entry(aggstate)->additional;
prepare_hash_slot(aggstate);
hash = TupleHashTableHash(perhash->hashtable, perhash->hashslot);
pergroup[setno] = lookup_hash_entry(aggstate, hash);
}
}
@ -2478,7 +2516,7 @@ ExecInitAgg(Agg *node, EState *estate, int eflags)
aggstate->hash_pergroup = pergroups;
find_hash_columns(aggstate);
build_hash_table(aggstate);
build_hash_tables(aggstate);
aggstate->table_filled = false;
}
@ -3498,7 +3536,7 @@ ExecReScanAgg(AggState *node)
{
ReScanExprContext(node->hashcontext);
/* Rebuild an empty hash table */
build_hash_table(node);
build_hash_tables(node);
node->table_filled = false;
/* iterator will be reset when the table is filled */
}