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Generate index-only scan tuple descriptor from the plan node's indextlist.

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Dept. of second thoughts: as long as we've got that tlist hanging around
anyway, we can apply ExecTypeFromTL to it to get a suitable descriptor for
the ScanTupleSlot.  This is a nicer solution than the previous one because
it eliminates some hard-wired knowledge about btree name_ops, and because
it avoids the somewhat shaky assumption that we needn't set up the scan
tuple descriptor in EXPLAIN_ONLY mode.  It doesn't change what actually
happens at run-time though, and I'm still a bit nervous about that.
This commit is contained in:
Tom Lane 2011-10-11 18:11:51 -04:00
parent e991930e8a
commit cb6771fb32
1 changed files with 16 additions and 52 deletions
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68
src/backend/executor/nodeIndexonlyscan.c
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@ -26,8 +26,6 @@
#include "access/relscan.h"
#include "access/visibilitymap.h"
#include "catalog/pg_opfamily.h"
#include "catalog/pg_type.h"
#include "executor/execdebug.h"
#include "executor/nodeIndexonlyscan.h"
#include "executor/nodeIndexscan.h"
@ -162,8 +160,10 @@ StoreIndexTuple(TupleTableSlot *slot, IndexTuple itup, Relation indexRel)
int i;
/*
* Note: we must use the index relation's tupdesc in index_getattr,
* not the slot's tupdesc, because of index_descriptor_hack().
* Note: we must use the index relation's tupdesc in index_getattr, not
* the slot's tupdesc, in case the latter has different datatypes (this
* happens for btree name_ops in particular). They'd better have the same
* number of columns though.
*/
Assert(slot->tts_tupleDescriptor->natts == nindexatts);
@ -173,45 +173,6 @@ StoreIndexTuple(TupleTableSlot *slot, IndexTuple itup, Relation indexRel)
ExecStoreVirtualTuple(slot);
}
/*
* index_descriptor_hack -- ugly kluge to make index's tupdesc OK for slot
*
* This is necessary because, alone among btree opclasses, name_ops uses
* a storage type (cstring) different from its input type. The index
* tuple descriptor will show "cstring", which is correct, but we have to
* expose "name" as the slot datatype or ExecEvalVar will whine. If we
* ever want to have any other cases with a different storage type, we ought
* to think of a cleaner solution than this.
*/
static TupleDesc
index_descriptor_hack(Relation indexRel)
{
TupleDesc tupdesc = RelationGetDescr(indexRel);
int i;
/* copy so we can scribble on it safely */
tupdesc = CreateTupleDescCopy(tupdesc);
for (i = 0; i < tupdesc->natts; i++)
{
if (indexRel->rd_opfamily[i] == NAME_BTREE_FAM_OID &&
tupdesc->attrs[i]->atttypid == CSTRINGOID)
{
tupdesc->attrs[i]->atttypid = NAMEOID;
/*
* We set attlen to match the type OID just in case anything looks
* at it. Note that this is safe only because StoreIndexTuple
* will insert the data as a virtual tuple, and we don't expect
* anything will try to materialize the scan tuple slot.
*/
tupdesc->attrs[i]->attlen = NAMEDATALEN;
}
}
return tupdesc;
}
/*
* IndexOnlyRecheck -- access method routine to recheck a tuple in EvalPlanQual
*
@ -426,9 +387,20 @@ ExecInitIndexOnlyScan(IndexOnlyScan *node, EState *estate, int eflags)
indexstate->ss.ss_currentScanDesc = NULL; /* no heap scan here */
/*
* Initialize result tuple type.
* Build the scan tuple type using the indextlist generated by the
* planner. We use this, rather than the index's physical tuple
* descriptor, because the latter contains storage column types not the
* types of the original datums. (It's the AM's responsibility to return
* suitable data anyway.)
*/
tupDesc = ExecTypeFromTL(node->indextlist, false);
ExecAssignScanType(&indexstate->ss, tupDesc);
/*
* Initialize result tuple type and projection info.
*/
ExecAssignResultTypeFromTL(&indexstate->ss.ps);
ExecAssignScanProjectionInfo(&indexstate->ss);
/*
* If we are just doing EXPLAIN (ie, aren't going to run the plan), stop
@ -449,14 +421,6 @@ ExecInitIndexOnlyScan(IndexOnlyScan *node, EState *estate, int eflags)
indexstate->ioss_RelationDesc = index_open(node->indexid,
relistarget ? NoLock : AccessShareLock);
/*
* Now we can get the scan tuple's type (which is the index's rowtype,
* not the heap's) and initialize result projection info.
*/
tupDesc = index_descriptor_hack(indexstate->ioss_RelationDesc);
ExecAssignScanType(&indexstate->ss, tupDesc);
ExecAssignScanProjectionInfo(&indexstate->ss);
/*
* Initialize index-specific scan state
*/