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Revise TupleTableSlot code to avoid unnecessary construction and disassembly

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of tuples when passing data up through multiple plan nodes.  A slot can now
hold either a normal "physical" HeapTuple, or a "virtual" tuple consisting
of Datum/isnull arrays.  Upper plan levels can usually just copy the Datum
arrays, avoiding heap_formtuple() and possible subsequent nocachegetattr()
calls to extract the data again.  This work extends Atsushi Ogawa's earlier
patch, which provided the key idea of adding Datum arrays to TupleTableSlots.
(I believe however that something like this was foreseen way back in Berkeley
days --- see the old comment on ExecProject.)  A test case involving many
levels of join of fairly wide tables (about 80 columns altogether) showed
about 3x overall speedup, though simple queries will probably not be
helped very much.

I have also duplicated some code in heaptuple.c in order to provide versions
of heap_formtuple and friends that use "bool" arrays to indicate null
attributes, instead of the old convention of "char" arrays containing either
'n' or ' '.  This provides a better match to the convention used by
ExecEvalExpr.  While I have not made a concerted effort to get rid of uses
of the old routines, I think they should be deprecated and eventually removed.
This commit is contained in:
Tom Lane
2005-03-16 21:38:10 +00:00
parent 712f053587
commit f97aebd162
44 changed files with 1766 additions and 934 deletions
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29
src/backend/commands/tablecmds.c
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@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/commands/tablecmds.c,v 1.146 2005/02/09 23:17:26 neilc Exp $
* $PostgreSQL: pgsql/src/backend/commands/tablecmds.c,v 1.147 2005/03/16 21:38:05 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -2455,7 +2455,7 @@ ATRewriteTable(AlteredTableInfo *tab, Oid OIDNewHeap)
{
ExprContext *econtext;
Datum *values;
char *nulls;
bool *isnull;
TupleTableSlot *oldslot;
TupleTableSlot *newslot;
HeapScanDesc scan;
@ -2471,17 +2471,15 @@ ATRewriteTable(AlteredTableInfo *tab, Oid OIDNewHeap)
* the tuples are the same, the tupDescs might not be (consider
* ADD COLUMN without a default).
*/
oldslot = MakeTupleTableSlot();
ExecSetSlotDescriptor(oldslot, oldTupDesc, false);
newslot = MakeTupleTableSlot();
ExecSetSlotDescriptor(newslot, newTupDesc, false);
oldslot = MakeSingleTupleTableSlot(oldTupDesc);
newslot = MakeSingleTupleTableSlot(newTupDesc);
/* Preallocate values/nulls arrays */
/* Preallocate values/isnull arrays */
i = Max(newTupDesc->natts, oldTupDesc->natts);
values = (Datum *) palloc(i * sizeof(Datum));
nulls = (char *) palloc(i * sizeof(char));
isnull = (bool *) palloc(i * sizeof(bool));
memset(values, 0, i * sizeof(Datum));
memset(nulls, 'n', i * sizeof(char));
memset(isnull, true, i * sizeof(bool));
/*
* Any attributes that are dropped according to the new tuple
@ -2512,11 +2510,11 @@ ATRewriteTable(AlteredTableInfo *tab, Oid OIDNewHeap)
if (newrel)
{
/* Extract data from old tuple */
heap_deformtuple(tuple, oldTupDesc, values, nulls);
heap_deform_tuple(tuple, oldTupDesc, values, isnull);
/* Set dropped attributes to null in new tuple */
foreach (lc, dropped_attrs)
nulls[lfirst_int(lc)] = 'n';
isnull[lfirst_int(lc)] = true;
/*
* Process supplied expressions to replace selected
@ -2528,16 +2526,11 @@ ATRewriteTable(AlteredTableInfo *tab, Oid OIDNewHeap)
foreach(l, tab->newvals)
{
NewColumnValue *ex = lfirst(l);
bool isNull;
values[ex->attnum - 1] = ExecEvalExpr(ex->exprstate,
econtext,
&isNull,
&isnull[ex->attnum - 1],
NULL);
if (isNull)
nulls[ex->attnum - 1] = 'n';
else
nulls[ex->attnum - 1] = ' ';
}
/*
@ -2545,7 +2538,7 @@ ATRewriteTable(AlteredTableInfo *tab, Oid OIDNewHeap)
* pfree it, since the per-tuple memory context will
* be reset shortly.
*/
tuple = heap_formtuple(newTupDesc, values, nulls);
tuple = heap_form_tuple(newTupDesc, values, isnull);
}
/* Now check any constraints on the possibly-changed tuple */