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Use MinimalTuple for tuple queues.

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This representation saves 8 bytes per tuple compared to HeapTuple, and
avoids the need to allocate, copy and free on the receiving side.

Gather can emit the returned MinimalTuple directly, but GatherMerge now
needs to make an explicit copy because it buffers multiple tuples at a
time.  That should be no worse than before.

Reviewed-by: Soumyadeep Chakraborty <soumyadeep2007@gmail.com>
Discussion: https://postgr.es/m/CA%2BhUKG%2B8T_ggoUTAE-U%3DA%2BOcPc4%3DB0nPPHcSfffuQhvXXjML6w%40mail.gmail.com
This commit is contained in:
Thomas Munro
2020-07-17 14:57:50 +12:00
parent d2bddc2500
commit cdc7169509
5 changed files with 51 additions and 47 deletions
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16
src/backend/executor/nodeGather.c
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@@ -46,7 +46,7 @@
static TupleTableSlot *ExecGather(PlanState *pstate);
static TupleTableSlot *gather_getnext(GatherState *gatherstate);
static HeapTuple gather_readnext(GatherState *gatherstate);
static MinimalTuple gather_readnext(GatherState *gatherstate);
static void ExecShutdownGatherWorkers(GatherState *node);
@@ -120,7 +120,7 @@ ExecInitGather(Gather *node, EState *estate, int eflags)
* Initialize funnel slot to same tuple descriptor as outer plan.
*/
gatherstate->funnel_slot = ExecInitExtraTupleSlot(estate, tupDesc,
&TTSOpsHeapTuple);
&TTSOpsMinimalTuple);
/*
* Gather doesn't support checking a qual (it's always more efficient to
@@ -266,7 +266,7 @@ gather_getnext(GatherState *gatherstate)
PlanState *outerPlan = outerPlanState(gatherstate);
TupleTableSlot *outerTupleSlot;
TupleTableSlot *fslot = gatherstate->funnel_slot;
HeapTuple tup;
MinimalTuple tup;
while (gatherstate->nreaders > 0 || gatherstate->need_to_scan_locally)
{
@@ -278,9 +278,9 @@ gather_getnext(GatherState *gatherstate)
if (HeapTupleIsValid(tup))
{
ExecStoreHeapTuple(tup, /* tuple to store */
fslot, /* slot to store the tuple */
true); /* pfree tuple when done with it */
ExecStoreMinimalTuple(tup, /* tuple to store */
fslot, /* slot to store the tuple */
false); /* don't pfree tuple */
return fslot;
}
}
@@ -308,7 +308,7 @@ gather_getnext(GatherState *gatherstate)
/*
* Attempt to read a tuple from one of our parallel workers.
*/
static HeapTuple
static MinimalTuple
gather_readnext(GatherState *gatherstate)
{
int nvisited = 0;
@@ -316,7 +316,7 @@ gather_readnext(GatherState *gatherstate)
for (;;)
{
TupleQueueReader *reader;
HeapTuple tup;
MinimalTuple tup;
bool readerdone;
/* Check for async events, particularly messages from workers. */