database/postgres
1
0
Fork 0
mirror of https://github.com/postgres/postgres.git synced 2025-07-12 21:01:52 +03:00
Code Activity

Rearrange the implementation of index-only scans.

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

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;