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Teach tuplestore.c to throw away data before the "mark" point when the caller

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is using mark/restore but not rewind or backward-scan capability.  Insert a
materialize plan node between a mergejoin and its inner child if the inner
child is a sort that is expected to spill to disk.  The materialize shields
the sort from the need to do mark/restore and thereby allows it to perform
its final merge pass on-the-fly; while the materialize itself is normally
cheap since it won't spill to disk unless the number of tuples with equal
key values exceeds work_mem.

Greg Stark, with some kibitzing from Tom Lane.
This commit is contained in:
Tom Lane
2007-05-21 17:57:35 +00:00
parent 3963574d13
commit 2415ad9831
8 changed files with 236 additions and 40 deletions
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36
src/backend/executor/nodeMaterial.c
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@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/executor/nodeMaterial.c,v 1.58 2007/01/05 22:19:28 momjian Exp $
* $PostgreSQL: pgsql/src/backend/executor/nodeMaterial.c,v 1.59 2007/05/21 17:57:33 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -56,10 +56,10 @@ ExecMaterial(MaterialState *node)
/*
* If first time through, and we need a tuplestore, initialize it.
*/
if (tuplestorestate == NULL && node->randomAccess)
if (tuplestorestate == NULL && node->eflags != 0)
{
tuplestorestate = tuplestore_begin_heap(true, false, work_mem);
tuplestore_set_eflags(tuplestorestate, node->eflags);
node->tuplestorestate = (void *) tuplestorestate;
}
@ -162,14 +162,14 @@ ExecInitMaterial(Material *node, EState *estate, int eflags)
matstate->ss.ps.state = estate;
/*
* We must have random access to the subplan output to do backward scan or
* mark/restore. We also prefer to materialize the subplan output if we
* might be called on to rewind and replay it many times. However, if none
* of these cases apply, we can skip storing the data.
* We must have a tuplestore buffering the subplan output to do backward
* scan or mark/restore. We also prefer to materialize the subplan output
* if we might be called on to rewind and replay it many times. However,
* if none of these cases apply, we can skip storing the data.
*/
matstate->randomAccess = (eflags & (EXEC_FLAG_REWIND |
EXEC_FLAG_BACKWARD |
EXEC_FLAG_MARK)) != 0;
matstate->eflags = (eflags & (EXEC_FLAG_REWIND |
EXEC_FLAG_BACKWARD |
EXEC_FLAG_MARK));
matstate->eof_underlying = false;
matstate->tuplestorestate = NULL;
@ -255,7 +255,7 @@ ExecEndMaterial(MaterialState *node)
void
ExecMaterialMarkPos(MaterialState *node)
{
Assert(node->randomAccess);
Assert(node->eflags & EXEC_FLAG_MARK);
/*
* if we haven't materialized yet, just return.
@ -275,7 +275,7 @@ ExecMaterialMarkPos(MaterialState *node)
void
ExecMaterialRestrPos(MaterialState *node)
{
Assert(node->randomAccess);
Assert(node->eflags & EXEC_FLAG_MARK);
/*
* if we haven't materialized yet, just return.
@ -300,7 +300,7 @@ ExecMaterialReScan(MaterialState *node, ExprContext *exprCtxt)
{
ExecClearTuple(node->ss.ps.ps_ResultTupleSlot);
if (node->randomAccess)
if (node->eflags != 0)
{
/*
* If we haven't materialized yet, just return. If outerplan' chgParam
@ -312,15 +312,21 @@ ExecMaterialReScan(MaterialState *node, ExprContext *exprCtxt)
/*
* If subnode is to be rescanned then we forget previous stored
* results; we have to re-read the subplan and re-store.
* results; we have to re-read the subplan and re-store. Also,
* if we told tuplestore it needn't support rescan, we lose and
* must re-read. (This last should not happen in common cases;
* else our caller lied by not passing EXEC_FLAG_REWIND to us.)
*
* Otherwise we can just rewind and rescan the stored output. The
* state of the subnode does not change.
*/
if (((PlanState *) node)->lefttree->chgParam != NULL)
if (((PlanState *) node)->lefttree->chgParam != NULL ||
(node->eflags & EXEC_FLAG_REWIND) == 0)
{
tuplestore_end((Tuplestorestate *) node->tuplestorestate);
node->tuplestorestate = NULL;
if (((PlanState *) node)->lefttree->chgParam == NULL)
ExecReScan(((PlanState *) node)->lefttree, exprCtxt);
node->eof_underlying = false;
}
else