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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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136
src/backend/optimizer/plan/createplan.c
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@ -53,8 +53,8 @@ static Material *create_material_plan(PlannerInfo *root, MaterialPath *best_path
static Plan *create_unique_plan(PlannerInfo *root, UniquePath *best_path);
static SeqScan *create_seqscan_plan(PlannerInfo *root, Path *best_path,
List *tlist, List *scan_clauses);
static IndexScan *create_indexscan_plan(PlannerInfo *root, IndexPath *best_path,
List *tlist, List *scan_clauses);
static Scan *create_indexscan_plan(PlannerInfo *root, IndexPath *best_path,
List *tlist, List *scan_clauses, bool indexonly);
static BitmapHeapScan *create_bitmap_scan_plan(PlannerInfo *root,
BitmapHeapPath *best_path,
List *tlist, List *scan_clauses);
@ -95,7 +95,12 @@ static SeqScan *make_seqscan(List *qptlist, List *qpqual, Index scanrelid);
static IndexScan *make_indexscan(List *qptlist, List *qpqual, Index scanrelid,
Oid indexid, List *indexqual, List *indexqualorig,
List *indexorderby, List *indexorderbyorig,
ScanDirection indexscandir, bool indexonly);
ScanDirection indexscandir);
static IndexOnlyScan *make_indexonlyscan(List *qptlist, List *qpqual,
Index scanrelid, Oid indexid,
List *indexqual, List *indexorderby,
List *indextlist,
ScanDirection indexscandir);
static BitmapIndexScan *make_bitmap_indexscan(Index scanrelid, Oid indexid,
List *indexqual,
List *indexqualorig);
@ -206,6 +211,7 @@ create_plan_recurse(PlannerInfo *root, Path *best_path)
{
case T_SeqScan:
case T_IndexScan:
case T_IndexOnlyScan:
case T_BitmapHeapScan:
case T_TidScan:
case T_SubqueryScan:
@ -274,10 +280,18 @@ create_scan_plan(PlannerInfo *root, Path *best_path)
*/
if (use_physical_tlist(root, rel))
{
tlist = build_physical_tlist(root, rel);
/* if fail because of dropped cols, use regular method */
if (tlist == NIL)
tlist = build_relation_tlist(rel);
if (best_path->pathtype == T_IndexOnlyScan)
{
/* For index-only scan, the preferred tlist is the index's */
tlist = copyObject(((IndexPath *) best_path)->indexinfo->indextlist);
}
else
{
tlist = build_physical_tlist(root, rel);
/* if fail because of dropped cols, use regular method */
if (tlist == NIL)
tlist = build_relation_tlist(rel);
}
}
else
tlist = build_relation_tlist(rel);
@ -302,7 +316,16 @@ create_scan_plan(PlannerInfo *root, Path *best_path)
plan = (Plan *) create_indexscan_plan(root,
(IndexPath *) best_path,
tlist,
scan_clauses);
scan_clauses,
false);
break;
case T_IndexOnlyScan:
plan = (Plan *) create_indexscan_plan(root,
(IndexPath *) best_path,
tlist,
scan_clauses,
true);
break;
case T_BitmapHeapScan:
@ -476,6 +499,7 @@ disuse_physical_tlist(Plan *plan, Path *path)
{
case T_SeqScan:
case T_IndexScan:
case T_IndexOnlyScan:
case T_BitmapHeapScan:
case T_TidScan:
case T_SubqueryScan:
@ -1044,16 +1068,23 @@ create_seqscan_plan(PlannerInfo *root, Path *best_path,
* Returns an indexscan plan for the base relation scanned by 'best_path'
* with restriction clauses 'scan_clauses' and targetlist 'tlist'.
*
* We use this for both plain IndexScans and IndexOnlyScans, because the
* qual preprocessing work is the same for both. Note that the caller tells
* us which to build --- we don't look at best_path->path.pathtype, because
* create_bitmap_subplan needs to be able to override the prior decision.
*
* The indexquals list of the path contains implicitly-ANDed qual conditions.
* The list can be empty --- then no index restrictions will be applied during
* the scan.
*/
static IndexScan *
static Scan *
create_indexscan_plan(PlannerInfo *root,
IndexPath *best_path,
List *tlist,
List *scan_clauses)
List *scan_clauses,
bool indexonly)
{
Scan *scan_plan;
List *indexquals = best_path->indexquals;
List *indexorderbys = best_path->indexorderbys;
Index baserelid = best_path->path.parent->relid;
@ -1063,7 +1094,6 @@ create_indexscan_plan(PlannerInfo *root,
List *fixed_indexquals;
List *fixed_indexorderbys;
ListCell *l;
IndexScan *scan_plan;
/* it should be a base rel... */
Assert(baserelid > 0);
@ -1077,7 +1107,7 @@ create_indexscan_plan(PlannerInfo *root,
/*
* The executor needs a copy with the indexkey on the left of each clause
* and with index attr numbers substituted for table ones.
* and with index Vars substituted for table ones.
*/
fixed_indexquals = fix_indexqual_references(root, best_path, indexquals);
@ -1175,20 +1205,29 @@ create_indexscan_plan(PlannerInfo *root,
}
/* Finally ready to build the plan node */
scan_plan = make_indexscan(tlist,
qpqual,
baserelid,
indexoid,
fixed_indexquals,
stripped_indexquals,
fixed_indexorderbys,
indexorderbys,
best_path->indexscandir,
best_path->indexonly);
if (indexonly)
scan_plan = (Scan *) make_indexonlyscan(tlist,
qpqual,
baserelid,
indexoid,
fixed_indexquals,
fixed_indexorderbys,
best_path->indexinfo->indextlist,
best_path->indexscandir);
else
scan_plan = (Scan *) make_indexscan(tlist,
qpqual,
baserelid,
indexoid,
fixed_indexquals,
stripped_indexquals,
fixed_indexorderbys,
indexorderbys,
best_path->indexscandir);
copy_path_costsize(&scan_plan->scan.plan, &best_path->path);
copy_path_costsize(&scan_plan->plan, &best_path->path);
/* use the indexscan-specific rows estimate, not the parent rel's */
scan_plan->scan.plan.plan_rows = best_path->rows;
scan_plan->plan.plan_rows = best_path->rows;
return scan_plan;
}
@ -1440,7 +1479,9 @@ create_bitmap_subplan(PlannerInfo *root, Path *bitmapqual,
ListCell *l;
/* Use the regular indexscan plan build machinery... */
iscan = create_indexscan_plan(root, ipath, NIL, NIL);
iscan = (IndexScan *) create_indexscan_plan(root, ipath,
NIL, NIL, false);
Assert(IsA(iscan, IndexScan));
/* then convert to a bitmap indexscan */
plan = (Plan *) make_bitmap_indexscan(iscan->scan.scanrelid,
iscan->indexid,
@ -2549,17 +2590,13 @@ fix_indexorderby_references(PlannerInfo *root, IndexPath *index_path,
/*
* fix_indexqual_operand
* Convert an indexqual expression to a Var referencing the index column.
*
* We represent index keys by Var nodes having varno == INDEX_VAR and varattno
* equal to the index's attribute number (index column position).
*/
static Node *
fix_indexqual_operand(Node *node, IndexOptInfo *index)
{
/*
* We represent index keys by Var nodes having the varno of the base table
* but varattno equal to the index's attribute number (index column
* position). This is a bit hokey ... would be cleaner to use a
* special-purpose node type that could not be mistaken for a regular Var.
* But it will do for now.
*/
Var *result;
int pos;
ListCell *indexpr_item;
@ -2583,6 +2620,7 @@ fix_indexqual_operand(Node *node, IndexOptInfo *index)
if (index->indexkeys[pos] == varatt)
{
result = (Var *) copyObject(node);
result->varno = INDEX_VAR;
result->varattno = pos + 1;
return (Node *) result;
}
@ -2606,7 +2644,7 @@ fix_indexqual_operand(Node *node, IndexOptInfo *index)
if (equal(node, indexkey))
{
/* Found a match */
result = makeVar(index->rel->relid, pos + 1,
result = makeVar(INDEX_VAR, pos + 1,
exprType(lfirst(indexpr_item)), -1,
exprCollation(lfirst(indexpr_item)),
0);
@ -2842,8 +2880,7 @@ make_indexscan(List *qptlist,
List *indexqualorig,
List *indexorderby,
List *indexorderbyorig,
ScanDirection indexscandir,
bool indexonly)
ScanDirection indexscandir)
{
IndexScan *node = makeNode(IndexScan);
Plan *plan = &node->scan.plan;
@ -2860,7 +2897,34 @@ make_indexscan(List *qptlist,
node->indexorderby = indexorderby;
node->indexorderbyorig = indexorderbyorig;
node->indexorderdir = indexscandir;
node->indexonly = indexonly;
return node;
}
static IndexOnlyScan *
make_indexonlyscan(List *qptlist,
List *qpqual,
Index scanrelid,
Oid indexid,
List *indexqual,
List *indexorderby,
List *indextlist,
ScanDirection indexscandir)
{
IndexOnlyScan *node = makeNode(IndexOnlyScan);
Plan *plan = &node->scan.plan;
/* cost should be inserted by caller */
plan->targetlist = qptlist;
plan->qual = qpqual;
plan->lefttree = NULL;
plan->righttree = NULL;
node->scan.scanrelid = scanrelid;
node->indexid = indexid;
node->indexqual = indexqual;
node->indexorderby = indexorderby;
node->indextlist = indextlist;
node->indexorderdir = indexscandir;
return node;
}