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Rearrange the implementation of index-only scans.

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This commit changes index-only scans so that data is read directly from the
index tuple without first generating a faux heap tuple.  The only immediate
benefit is that indexes on system columns (such as OID) can be used in
index-only scans, but this is necessary infrastructure if we are ever to
support index-only scans on expression indexes.  The executor is now ready
for that, though the planner still needs substantial work to recognize
the possibility.

To do this, Vars in index-only plan nodes have to refer to index columns
not heap columns.  I introduced a new special varno, INDEX_VAR, to mark
such Vars to avoid confusion.  (In passing, this commit renames the two
existing special varnos to OUTER_VAR and INNER_VAR.)  This allows
ruleutils.c to handle them with logic similar to what we use for subplan
reference Vars.

Since index-only scans are now fundamentally different from regular
indexscans so far as their expression subtrees are concerned, I also chose
to change them to have their own plan node type (and hence, their own
executor source file).
This commit is contained in:
Tom Lane
2011-10-11 14:20:06 -04:00
parent fa351d5a0d
commit a0185461dd
34 changed files with 1312 additions and 419 deletions
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29
src/backend/nodes/copyfuncs.c
View File

@ -370,7 +370,31 @@ _copyIndexScan(IndexScan *from)
COPY_NODE_FIELD(indexorderby);
COPY_NODE_FIELD(indexorderbyorig);
COPY_SCALAR_FIELD(indexorderdir);
COPY_SCALAR_FIELD(indexonly);
return newnode;
}
/*
* _copyIndexOnlyScan
*/
static IndexOnlyScan *
_copyIndexOnlyScan(IndexOnlyScan *from)
{
IndexOnlyScan *newnode = makeNode(IndexOnlyScan);
/*
* copy node superclass fields
*/
CopyScanFields((Scan *) from, (Scan *) newnode);
/*
* copy remainder of node
*/
COPY_SCALAR_FIELD(indexid);
COPY_NODE_FIELD(indexqual);
COPY_NODE_FIELD(indexorderby);
COPY_NODE_FIELD(indextlist);
COPY_SCALAR_FIELD(indexorderdir);
return newnode;
}
@ -3871,6 +3895,9 @@ copyObject(void *from)
case T_IndexScan:
retval = _copyIndexScan(from);
break;
case T_IndexOnlyScan:
retval = _copyIndexOnlyScan(from);
break;
case T_BitmapIndexScan:
retval = _copyBitmapIndexScan(from);
break;

22
src/backend/nodes/outfuncs.c
View File

@ -447,7 +447,20 @@ _outIndexScan(StringInfo str, IndexScan *node)
WRITE_NODE_FIELD(indexorderby);
WRITE_NODE_FIELD(indexorderbyorig);
WRITE_ENUM_FIELD(indexorderdir, ScanDirection);
WRITE_BOOL_FIELD(indexonly);
}
static void
_outIndexOnlyScan(StringInfo str, IndexOnlyScan *node)
{
WRITE_NODE_TYPE("INDEXONLYSCAN");
_outScanInfo(str, (Scan *) node);
WRITE_OID_FIELD(indexid);
WRITE_NODE_FIELD(indexqual);
WRITE_NODE_FIELD(indexorderby);
WRITE_NODE_FIELD(indextlist);
WRITE_ENUM_FIELD(indexorderdir, ScanDirection);
}
static void
@ -1501,7 +1514,6 @@ _outIndexPath(StringInfo str, IndexPath *node)
WRITE_NODE_FIELD(indexorderbys);
WRITE_BOOL_FIELD(isjoininner);
WRITE_ENUM_FIELD(indexscandir, ScanDirection);
WRITE_BOOL_FIELD(indexonly);
WRITE_FLOAT_FIELD(indextotalcost, "%.2f");
WRITE_FLOAT_FIELD(indexselectivity, "%.4f");
WRITE_FLOAT_FIELD(rows, "%.0f");
@ -1752,8 +1764,9 @@ _outIndexOptInfo(StringInfo str, IndexOptInfo *node)
WRITE_FLOAT_FIELD(tuples, "%.0f");
WRITE_INT_FIELD(ncolumns);
WRITE_OID_FIELD(relam);
WRITE_NODE_FIELD(indexprs);
/* indexprs is redundant since we print indextlist */
WRITE_NODE_FIELD(indpred);
WRITE_NODE_FIELD(indextlist);
WRITE_BOOL_FIELD(predOK);
WRITE_BOOL_FIELD(unique);
WRITE_BOOL_FIELD(hypothetical);
@ -2707,6 +2720,9 @@ _outNode(StringInfo str, void *obj)
case T_IndexScan:
_outIndexScan(str, obj);
break;
case T_IndexOnlyScan:
_outIndexOnlyScan(str, obj);
break;
case T_BitmapIndexScan:
_outBitmapIndexScan(str, obj);
break;

8
src/backend/nodes/print.c
View File

@ -320,14 +320,18 @@ print_expr(Node *expr, List *rtable)
switch (var->varno)
{
case INNER:
case INNER_VAR:
relname = "INNER";
attname = "?";
break;
case OUTER:
case OUTER_VAR:
relname = "OUTER";
attname = "?";
break;
case INDEX_VAR:
relname = "INDEX";
attname = "?";
break;
default:
{
RangeTblEntry *rte;