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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

138
src/backend/optimizer/plan/setrefs.c
View File

@ -63,6 +63,7 @@ typedef struct
{
PlannerInfo *root;
indexed_tlist *subplan_itlist;
Index newvarno;
int rtoffset;
} fix_upper_expr_context;
@ -81,6 +82,9 @@ typedef struct
((List *) fix_scan_expr(root, (Node *) (lst), rtoffset))
static Plan *set_plan_refs(PlannerInfo *root, Plan *plan, int rtoffset);
static Plan *set_indexonlyscan_references(PlannerInfo *root,
IndexOnlyScan *plan,
int rtoffset);
static Plan *set_subqueryscan_references(PlannerInfo *root,
SubqueryScan *plan,
int rtoffset);
@ -113,6 +117,7 @@ static Node *fix_join_expr_mutator(Node *node,
static Node *fix_upper_expr(PlannerInfo *root,
Node *node,
indexed_tlist *subplan_itlist,
Index newvarno,
int rtoffset);
static Node *fix_upper_expr_mutator(Node *node,
fix_upper_expr_context *context);
@ -234,6 +239,16 @@ set_plan_references(PlannerInfo *root, Plan *plan)
newrte->relid);
}
/*
* Check for RT index overflow; it's very unlikely, but if it did happen,
* the executor would get confused by varnos that match the special varno
* values.
*/
if (IS_SPECIAL_VARNO(list_length(glob->finalrtable)))
ereport(ERROR,
(errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
errmsg("too many range table entries")));
/*
* Adjust RT indexes of PlanRowMarks and add to final rowmarks list
*/
@ -305,6 +320,13 @@ set_plan_refs(PlannerInfo *root, Plan *plan, int rtoffset)
fix_scan_list(root, splan->indexorderbyorig, rtoffset);
}
break;
case T_IndexOnlyScan:
{
IndexOnlyScan *splan = (IndexOnlyScan *) plan;
return set_indexonlyscan_references(root, splan, rtoffset);
}
break;
case T_BitmapIndexScan:
{
BitmapIndexScan *splan = (BitmapIndexScan *) plan;
@ -652,6 +674,49 @@ set_plan_refs(PlannerInfo *root, Plan *plan, int rtoffset)
return plan;
}
/*
* set_indexonlyscan_references
* Do set_plan_references processing on an IndexOnlyScan
*
* This is unlike the handling of a plain IndexScan because we have to
* convert Vars referencing the heap into Vars referencing the index.
* We can use the fix_upper_expr machinery for that, by working from a
* targetlist describing the index columns.
*/
static Plan *
set_indexonlyscan_references(PlannerInfo *root,
IndexOnlyScan *plan,
int rtoffset)
{
indexed_tlist *index_itlist;
index_itlist = build_tlist_index(plan->indextlist);
plan->scan.scanrelid += rtoffset;
plan->scan.plan.targetlist = (List *)
fix_upper_expr(root,
(Node *) plan->scan.plan.targetlist,
index_itlist,
INDEX_VAR,
rtoffset);
plan->scan.plan.qual = (List *)
fix_upper_expr(root,
(Node *) plan->scan.plan.qual,
index_itlist,
INDEX_VAR,
rtoffset);
/* indexqual is already transformed to reference index columns */
plan->indexqual = fix_scan_list(root, plan->indexqual, rtoffset);
/* indexorderby is already transformed to reference index columns */
plan->indexorderby = fix_scan_list(root, plan->indexorderby, rtoffset);
/* indextlist must NOT be transformed to reference index columns */
plan->indextlist = fix_scan_list(root, plan->indextlist, rtoffset);
pfree(index_itlist);
return (Plan *) plan;
}
/*
* set_subqueryscan_references
* Do set_plan_references processing on a SubqueryScan
@ -919,11 +984,13 @@ fix_scan_expr_mutator(Node *node, fix_scan_expr_context *context)
Assert(var->varlevelsup == 0);
/*
* We should not see any Vars marked INNER or OUTER.
* We should not see any Vars marked INNER_VAR or OUTER_VAR. But an
* indexqual expression could contain INDEX_VAR Vars.
*/
Assert(var->varno != INNER);
Assert(var->varno != OUTER);
var->varno += context->rtoffset;
Assert(var->varno != INNER_VAR);
Assert(var->varno != OUTER_VAR);
if (!IS_SPECIAL_VARNO(var->varno))
var->varno += context->rtoffset;
if (var->varnoold > 0)
var->varnoold += context->rtoffset;
return (Node *) var;
@ -932,9 +999,10 @@ fix_scan_expr_mutator(Node *node, fix_scan_expr_context *context)
{
CurrentOfExpr *cexpr = (CurrentOfExpr *) copyObject(node);
Assert(cexpr->cvarno != INNER);
Assert(cexpr->cvarno != OUTER);
cexpr->cvarno += context->rtoffset;
Assert(cexpr->cvarno != INNER_VAR);
Assert(cexpr->cvarno != OUTER_VAR);
if (!IS_SPECIAL_VARNO(cexpr->cvarno))
cexpr->cvarno += context->rtoffset;
return (Node *) cexpr;
}
if (IsA(node, PlaceHolderVar))
@ -963,9 +1031,9 @@ fix_scan_expr_walker(Node *node, fix_scan_expr_context *context)
/*
* set_join_references
* Modify the target list and quals of a join node to reference its
* subplans, by setting the varnos to OUTER or INNER and setting attno
* values to the result domain number of either the corresponding outer
* or inner join tuple item. Also perform opcode lookup for these
* subplans, by setting the varnos to OUTER_VAR or INNER_VAR and setting
* attno values to the result domain number of either the corresponding
* outer or inner join tuple item. Also perform opcode lookup for these
* expressions. and add regclass OIDs to root->glob->relationOids.
*/
static void
@ -1012,6 +1080,7 @@ set_join_references(PlannerInfo *root, Join *join, int rtoffset)
nlp->paramval = (Var *) fix_upper_expr(root,
(Node *) nlp->paramval,
outer_itlist,
OUTER_VAR,
rtoffset);
}
}
@ -1083,17 +1152,19 @@ set_upper_references(PlannerInfo *root, Plan *plan, int rtoffset)
search_indexed_tlist_for_sortgroupref((Node *) tle->expr,
tle->ressortgroupref,
subplan_itlist,
OUTER);
OUTER_VAR);
if (!newexpr)
newexpr = fix_upper_expr(root,
(Node *) tle->expr,
subplan_itlist,
OUTER_VAR,
rtoffset);
}
else
newexpr = fix_upper_expr(root,
(Node *) tle->expr,
subplan_itlist,
OUTER_VAR,
rtoffset);
tle = flatCopyTargetEntry(tle);
tle->expr = (Expr *) newexpr;
@ -1105,6 +1176,7 @@ set_upper_references(PlannerInfo *root, Plan *plan, int rtoffset)
fix_upper_expr(root,
(Node *) plan->qual,
subplan_itlist,
OUTER_VAR,
rtoffset);
pfree(subplan_itlist);
@ -1113,7 +1185,7 @@ set_upper_references(PlannerInfo *root, Plan *plan, int rtoffset)
/*
* set_dummy_tlist_references
* Replace the targetlist of an upper-level plan node with a simple
* list of OUTER references to its child.
* list of OUTER_VAR references to its child.
*
* This is used for plan types like Sort and Append that don't evaluate
* their targetlists. Although the executor doesn't care at all what's in
@ -1136,7 +1208,7 @@ set_dummy_tlist_references(Plan *plan, int rtoffset)
Var *oldvar = (Var *) tle->expr;
Var *newvar;
newvar = makeVar(OUTER,
newvar = makeVar(OUTER_VAR,
tle->resno,
exprType((Node *) oldvar),
exprTypmod((Node *) oldvar),
@ -1382,11 +1454,12 @@ search_indexed_tlist_for_sortgroupref(Node *node,
* relation target lists. Also perform opcode lookup and add
* regclass OIDs to root->glob->relationOids.
*
* This is used in two different scenarios: a normal join clause, where
* all the Vars in the clause *must* be replaced by OUTER or INNER references;
* and a RETURNING clause, which may contain both Vars of the target relation
* and Vars of other relations. In the latter case we want to replace the
* other-relation Vars by OUTER references, while leaving target Vars alone.
* This is used in two different scenarios: a normal join clause, where all
* the Vars in the clause *must* be replaced by OUTER_VAR or INNER_VAR
* references; and a RETURNING clause, which may contain both Vars of the
* target relation and Vars of other relations. In the latter case we want
* to replace the other-relation Vars by OUTER_VAR references, while leaving
* target Vars alone.
*
* For a normal join, acceptable_rel should be zero so that any failure to
* match a Var will be reported as an error. For the RETURNING case, pass
@ -1435,7 +1508,7 @@ fix_join_expr_mutator(Node *node, fix_join_expr_context *context)
/* First look for the var in the input tlists */
newvar = search_indexed_tlist_for_var(var,
context->outer_itlist,
OUTER,
OUTER_VAR,
context->rtoffset);
if (newvar)
return (Node *) newvar;
@ -1443,7 +1516,7 @@ fix_join_expr_mutator(Node *node, fix_join_expr_context *context)
{
newvar = search_indexed_tlist_for_var(var,
context->inner_itlist,
INNER,
INNER_VAR,
context->rtoffset);
if (newvar)
return (Node *) newvar;
@ -1470,7 +1543,7 @@ fix_join_expr_mutator(Node *node, fix_join_expr_context *context)
{
newvar = search_indexed_tlist_for_non_var((Node *) phv,
context->outer_itlist,
OUTER);
OUTER_VAR);
if (newvar)
return (Node *) newvar;
}
@ -1478,7 +1551,7 @@ fix_join_expr_mutator(Node *node, fix_join_expr_context *context)
{
newvar = search_indexed_tlist_for_non_var((Node *) phv,
context->inner_itlist,
INNER);
INNER_VAR);
if (newvar)
return (Node *) newvar;
}
@ -1491,7 +1564,7 @@ fix_join_expr_mutator(Node *node, fix_join_expr_context *context)
{
newvar = search_indexed_tlist_for_non_var(node,
context->outer_itlist,
OUTER);
OUTER_VAR);
if (newvar)
return (Node *) newvar;
}
@ -1499,7 +1572,7 @@ fix_join_expr_mutator(Node *node, fix_join_expr_context *context)
{
newvar = search_indexed_tlist_for_non_var(node,
context->inner_itlist,
INNER);
INNER_VAR);
if (newvar)
return (Node *) newvar;
}
@ -1516,7 +1589,7 @@ fix_join_expr_mutator(Node *node, fix_join_expr_context *context)
* root->glob->relationOids.
*
* This is used to fix up target and qual expressions of non-join upper-level
* plan nodes.
* plan nodes, as well as index-only scan nodes.
*
* An error is raised if no matching var can be found in the subplan tlist
* --- so this routine should only be applied to nodes whose subplans'
@ -1529,23 +1602,26 @@ fix_join_expr_mutator(Node *node, fix_join_expr_context *context)
* subplan tlist is just a flattened list of Vars.)
*
* 'node': the tree to be fixed (a target item or qual)
* 'subplan_itlist': indexed target list for subplan
* 'subplan_itlist': indexed target list for subplan (or index)
* 'newvarno': varno to use for Vars referencing tlist elements
* 'rtoffset': how much to increment varnoold by
*
* The resulting tree is a copy of the original in which all Var nodes have
* varno = OUTER, varattno = resno of corresponding subplan target.
* varno = newvarno, varattno = resno of corresponding targetlist element.
* The original tree is not modified.
*/
static Node *
fix_upper_expr(PlannerInfo *root,
Node *node,
indexed_tlist *subplan_itlist,
Index newvarno,
int rtoffset)
{
fix_upper_expr_context context;
context.root = root;
context.subplan_itlist = subplan_itlist;
context.newvarno = newvarno;
context.rtoffset = rtoffset;
return fix_upper_expr_mutator(node, &context);
}
@ -1563,7 +1639,7 @@ fix_upper_expr_mutator(Node *node, fix_upper_expr_context *context)
newvar = search_indexed_tlist_for_var(var,
context->subplan_itlist,
OUTER,
context->newvarno,
context->rtoffset);
if (!newvar)
elog(ERROR, "variable not found in subplan target list");
@ -1578,7 +1654,7 @@ fix_upper_expr_mutator(Node *node, fix_upper_expr_context *context)
{
newvar = search_indexed_tlist_for_non_var((Node *) phv,
context->subplan_itlist,
OUTER);
context->newvarno);
if (newvar)
return (Node *) newvar;
}
@ -1590,7 +1666,7 @@ fix_upper_expr_mutator(Node *node, fix_upper_expr_context *context)
{
newvar = search_indexed_tlist_for_non_var(node,
context->subplan_itlist,
OUTER);
context->newvarno);
if (newvar)
return (Node *) newvar;
}
@ -1610,7 +1686,7 @@ fix_upper_expr_mutator(Node *node, fix_upper_expr_context *context)
* table should be left alone, however (the executor will evaluate them
* using the actual heap tuple, after firing triggers if any). In the
* adjusted RETURNING list, result-table Vars will still have their
* original varno, but Vars for other rels will have varno OUTER.
* original varno, but Vars for other rels will have varno OUTER_VAR.
*
* We also must perform opcode lookup and add regclass OIDs to
* root->glob->relationOids.