database/postgres
1
0
Fork 0
mirror of https://github.com/postgres/postgres.git synced 2025-06-14 18:42:34 +03:00
Code Activity

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

Browse Source 
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
Download Patch File Download Diff File Expand all files Collapse all files

38
src/backend/executor/nodeMergejoin.c
View File

@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/executor/nodeMergejoin.c,v 1.87 2007/02/02 00:07:03 tgl Exp $
* $PostgreSQL: pgsql/src/backend/executor/nodeMergejoin.c,v 1.88 2007/05/21 17:57:33 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -706,6 +706,9 @@ ExecMergeJoin(MergeJoinState *node)
}
else
{
/* Mark before advancing, if wanted */
if (node->mj_ExtraMarks)
ExecMarkPos(innerPlan);
/* Stay in same state to fetch next inner tuple */
if (doFillInner)
{
@ -830,6 +833,9 @@ ExecMergeJoin(MergeJoinState *node)
* now we get the next inner tuple, if any. If there's none,
* advance to next outer tuple (which may be able to join to
* previously marked tuples).
*
* NB: must NOT do "extraMarks" here, since we may need to
* return to previously marked tuples.
*/
innerTupleSlot = ExecProcNode(innerPlan);
node->mj_InnerTupleSlot = innerTupleSlot;
@ -1140,6 +1146,9 @@ ExecMergeJoin(MergeJoinState *node)
break;
/*
* SKIPOUTER_ADVANCE: advance over an outer tuple that is
* known not to join to any inner tuple.
*
* Before advancing, we check to see if we must emit an
* outer-join fill tuple for this outer tuple.
*/
@ -1204,6 +1213,9 @@ ExecMergeJoin(MergeJoinState *node)
break;
/*
* SKIPINNER_ADVANCE: advance over an inner tuple that is
* known not to join to any outer tuple.
*
* Before advancing, we check to see if we must emit an
* outer-join fill tuple for this inner tuple.
*/
@ -1225,6 +1237,10 @@ ExecMergeJoin(MergeJoinState *node)
return result;
}
/* Mark before advancing, if wanted */
if (node->mj_ExtraMarks)
ExecMarkPos(innerPlan);
/*
* now we get the next inner tuple, if any
*/
@ -1295,6 +1311,10 @@ ExecMergeJoin(MergeJoinState *node)
return result;
}
/* Mark before advancing, if wanted */
if (node->mj_ExtraMarks)
ExecMarkPos(innerPlan);
/*
* now we get the next inner tuple, if any
*/
@ -1425,6 +1445,22 @@ ExecInitMergeJoin(MergeJoin *node, EState *estate, int eflags)
innerPlanState(mergestate) = ExecInitNode(innerPlan(node), estate,
eflags | EXEC_FLAG_MARK);
/*
* For certain types of inner child nodes, it is advantageous to issue
* MARK every time we advance past an inner tuple we will never return
* to. For other types, MARK on a tuple we cannot return to is a waste
* of cycles. Detect which case applies and set mj_ExtraMarks if we
* want to issue "unnecessary" MARK calls.
*
* Currently, only Material wants the extra MARKs, and it will be helpful
* only if eflags doesn't specify REWIND.
*/
if (IsA(innerPlan(node), Material) &&
(eflags & EXEC_FLAG_REWIND) == 0)
mergestate->mj_ExtraMarks = true;
else
mergestate->mj_ExtraMarks = false;
#define MERGEJOIN_NSLOTS 4
/*