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Avoid allocating unnecessary zero-sized array. 

If there are no aggregates, there is no need to allocate an array of
zero AggStatePerGroupData elements.
This commit is contained in:
Jeff Davis 2020-03-24 18:19:34 -07:00
parent b150a76793
commit 3649133b14
1 changed files with 22 additions and 7 deletions
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29
src/backend/executor/nodeAgg.c
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@ -400,7 +400,8 @@ static int hash_choose_num_partitions(uint64 input_groups,
double hashentrysize,
int used_bits,
int *log2_npartittions);
static AggStatePerGroup lookup_hash_entry(AggState *aggstate, uint32 hash);
static AggStatePerGroup lookup_hash_entry(AggState *aggstate, uint32 hash,
bool *in_hash_table);
static void lookup_hash_entries(AggState *aggstate);
static TupleTableSlot *agg_retrieve_direct(AggState *aggstate);
static void agg_fill_hash_table(AggState *aggstate);
@ -1968,10 +1969,11 @@ hash_choose_num_partitions(uint64 input_groups, double hashentrysize,
*
* If in "spill mode", then only find existing hashtable entries; don't create
* new ones. If a tuple's group is not already present in the hash table for
* the current grouping set, return NULL and the caller will spill it to disk.
* the current grouping set, assign *in_hash_table=false and the caller will
* spill it to disk.
*/
static AggStatePerGroup
lookup_hash_entry(AggState *aggstate, uint32 hash)
lookup_hash_entry(AggState *aggstate, uint32 hash, bool *in_hash_table)
{
AggStatePerHash perhash = &aggstate->perhash[aggstate->current_set];
TupleTableSlot *hashslot = perhash->hashslot;
@ -1987,7 +1989,12 @@ lookup_hash_entry(AggState *aggstate, uint32 hash)
hash);
if (entry == NULL)
{
*in_hash_table = false;
return NULL;
}
else
*in_hash_table = true;
if (isnew)
{
@ -1997,9 +2004,14 @@ lookup_hash_entry(AggState *aggstate, uint32 hash)
aggstate->hash_ngroups_current++;
hash_agg_check_limits(aggstate);
/* no need to allocate or initialize per-group state */
if (aggstate->numtrans == 0)
return NULL;
pergroup = (AggStatePerGroup)
MemoryContextAlloc(perhash->hashtable->tablecxt,
sizeof(AggStatePerGroupData) * aggstate->numtrans);
entry->additional = pergroup;
/*
@ -2046,14 +2058,15 @@ lookup_hash_entries(AggState *aggstate)
{
AggStatePerHash perhash = &aggstate->perhash[setno];
uint32 hash;
bool in_hash_table;
select_current_set(aggstate, setno, true);
prepare_hash_slot(aggstate);
hash = TupleHashTableHash(perhash->hashtable, perhash->hashslot);
pergroup[setno] = lookup_hash_entry(aggstate, hash);
pergroup[setno] = lookup_hash_entry(aggstate, hash, &in_hash_table);
/* check to see if we need to spill the tuple for this grouping set */
if (pergroup[setno] == NULL)
if (!in_hash_table)
{
HashAggSpill *spill = &aggstate->hash_spills[setno];
TupleTableSlot *slot = aggstate->tmpcontext->ecxt_outertuple;
@ -2587,6 +2600,7 @@ agg_refill_hash_table(AggState *aggstate)
TupleTableSlot *slot = aggstate->hash_spill_slot;
MinimalTuple tuple;
uint32 hash;
bool in_hash_table;
CHECK_FOR_INTERRUPTS();
@ -2598,9 +2612,10 @@ agg_refill_hash_table(AggState *aggstate)
aggstate->tmpcontext->ecxt_outertuple = slot;
prepare_hash_slot(aggstate);
aggstate->hash_pergroup[batch->setno] = lookup_hash_entry(aggstate, hash);
aggstate->hash_pergroup[batch->setno] = lookup_hash_entry(
aggstate, hash, &in_hash_table);
if (aggstate->hash_pergroup[batch->setno] != NULL)
if (in_hash_table)
{
/* Advance the aggregates (or combine functions) */
advance_aggregates(aggstate);