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Make sequential scans parallel-aware.

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In addition, this path fills in a number of missing bits and pieces in
the parallel infrastructure.  Paths and plans now have a parallel_aware
flag indicating whether whatever parallel-aware logic they have should
be engaged.  It is believed that we will need this flag for a number of
path/plan types, not just sequential scans, which is why the flag is
generic rather than part of the SeqScan structures specifically.
Also, execParallel.c now gives parallel nodes a chance to initialize
their PlanState nodes from the DSM during parallel worker startup.

Amit Kapila, with a fair amount of adjustment by me.  Review of previous
patch versions by Haribabu Kommi and others.
This commit is contained in:
Robert Haas
2015-11-11 08:57:52 -05:00
parent f764ecd81b
commit f0661c4e8c
18 changed files with 254 additions and 73 deletions
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54
src/backend/executor/execParallel.c
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@ -25,6 +25,7 @@
#include "executor/execParallel.h"
#include "executor/executor.h"
#include "executor/nodeSeqscan.h"
#include "executor/tqueue.h"
#include "nodes/nodeFuncs.h"
#include "optimizer/planmain.h"
@ -167,10 +168,16 @@ ExecParallelEstimate(PlanState *planstate, ExecParallelEstimateContext *e)
/* Count this node. */
e->nnodes++;
/*
* XXX. Call estimators for parallel-aware nodes here, when we have
* some.
*/
/* Call estimators for parallel-aware nodes. */
switch (nodeTag(planstate))
{
case T_SeqScanState:
ExecSeqScanEstimate((SeqScanState *) planstate,
e->pcxt);
break;
default:
break;
}
return planstate_tree_walker(planstate, ExecParallelEstimate, e);
}
@ -205,10 +212,16 @@ ExecParallelInitializeDSM(PlanState *planstate,
/* Count this node. */
d->nnodes++;
/*
* XXX. Call initializers for parallel-aware plan nodes, when we have
* some.
*/
/* Call initializers for parallel-aware plan nodes. */
switch (nodeTag(planstate))
{
case T_SeqScanState:
ExecSeqScanInitializeDSM((SeqScanState *) planstate,
d->pcxt);
break;
default:
break;
}
return planstate_tree_walker(planstate, ExecParallelInitializeDSM, d);
}
@ -574,6 +587,30 @@ ExecParallelReportInstrumentation(PlanState *planstate,
instrumentation);
}
/*
* Initialize the PlanState and its descendents with the information
* retrieved from shared memory. This has to be done once the PlanState
* is allocated and initialized by executor; that is, after ExecutorStart().
*/
static bool
ExecParallelInitializeWorker(PlanState *planstate, shm_toc *toc)
{
if (planstate == NULL)
return false;
/* Call initializers for parallel-aware plan nodes. */
switch (nodeTag(planstate))
{
case T_SeqScanState:
ExecSeqScanInitializeWorker((SeqScanState *) planstate, toc);
break;
default:
break;
}
return planstate_tree_walker(planstate, ExecParallelInitializeWorker, toc);
}
/*
* Main entrypoint for parallel query worker processes.
*
@ -610,6 +647,7 @@ ParallelQueryMain(dsm_segment *seg, shm_toc *toc)
/* Start up the executor, have it run the plan, and then shut it down. */
ExecutorStart(queryDesc, 0);
ExecParallelInitializeWorker(queryDesc->planstate, toc);
ExecutorRun(queryDesc, ForwardScanDirection, 0L);
ExecutorFinish(queryDesc);