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Modify partial-index-predicate applicability tester to test whether

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clauses are equal(), before trying to match them up using btree opclass
inference rules.  This allows it to recognize many simple cases involving
non-btree operations, for example 'x IS NULL'.  Clean up code a little.
This commit is contained in:
Tom Lane
2001-08-06 18:09:45 +00:00
parent 7d6fbe15a2
commit 246793469e
3 changed files with 98 additions and 82 deletions
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147
src/backend/optimizer/path/indxpath.c
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@ -9,7 +9,7 @@
*
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/optimizer/path/indxpath.c,v 1.109 2001/07/16 05:06:58 tgl Exp $
* $Header: /cvsroot/pgsql/src/backend/optimizer/path/indxpath.c,v 1.110 2001/08/06 18:09:45 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -79,10 +79,10 @@ static bool match_clause_to_indexkey(RelOptInfo *rel, IndexOptInfo *index,
Expr *clause, bool join);
static bool pred_test(List *predicate_list, List *restrictinfo_list,
List *joininfo_list);
static bool one_pred_test(Expr *predicate, List *restrictinfo_list);
static bool one_pred_clause_expr_test(Expr *predicate, Node *clause);
static bool one_pred_clause_test(Expr *predicate, Node *clause);
static bool clause_pred_clause_test(Expr *predicate, Node *clause);
static bool pred_test_restrict_list(Expr *predicate, List *restrictinfo_list);
static bool pred_test_recurse_clause(Expr *predicate, Node *clause);
static bool pred_test_recurse_pred(Expr *predicate, Node *clause);
static bool pred_test_simple_clause(Expr *predicate, Node *clause);
static void indexable_joinclauses(RelOptInfo *rel, IndexOptInfo *index,
List *joininfo_list, List *restrictinfo_list,
List **clausegroups, List **outerrelids);
@ -197,7 +197,8 @@ create_index_paths(Query *root, RelOptInfo *rel)
* merging or final output ordering.
*
* If there is a predicate, consider it anyway since the index
* predicate has already been found to match the query.
* predicate has already been found to match the query. The
* selectivity of the predicate might alone make the index useful.
*/
if (restrictclauses != NIL ||
useful_pathkeys != NIL ||
@ -959,15 +960,13 @@ indexable_operator(Expr *clause, Oid opclass, Oid relam,
* ANDs in the predicate first, then reduces the qualification
* clauses down to their constituent terms, and iterates over ORs
* in the predicate last. This order is important to make the test
* succeed whenever possible (assuming the predicate has been
* successfully cnfify()-ed). --Nels, Jan '93
* succeed whenever possible (assuming the predicate has been converted
* to CNF format). --Nels, Jan '93
*/
static bool
pred_test(List *predicate_list, List *restrictinfo_list, List *joininfo_list)
{
List *pred,
*items,
*item;
List *pred;
/*
* Note: if Postgres tried to optimize queries by forming equivalence
@ -977,6 +976,9 @@ pred_test(List *predicate_list, List *restrictinfo_list, List *joininfo_list)
* here with joininfo_list to do more complete tests for the usability
* of a partial index. For now, the test only uses restriction
* clauses (those in restrictinfo_list). --Nels, Dec '92
*
* XXX as of 7.1, equivalence class info *is* available. Consider
* improving this code as foreseen by Nels.
*/
if (predicate_list == NIL)
@ -989,19 +991,10 @@ pred_test(List *predicate_list, List *restrictinfo_list, List *joininfo_list)
{
/*
* if any clause is not implied, the whole predicate is not
* implied. Note that checking for sub-ANDs here is redundant
* if the predicate has been cnfify()-ed.
* implied. Note we assume that any sub-ANDs have been flattened
* when the predicate was fed through canonicalize_qual().
*/
if (and_clause(lfirst(pred)))
{
items = ((Expr *) lfirst(pred))->args;
foreach(item, items)
{
if (!one_pred_test(lfirst(item), restrictinfo_list))
return false;
}
}
else if (!one_pred_test(lfirst(pred), restrictinfo_list))
if (!pred_test_restrict_list(lfirst(pred), restrictinfo_list))
return false;
}
return true;
@ -1009,23 +1002,22 @@ pred_test(List *predicate_list, List *restrictinfo_list, List *joininfo_list)
/*
* one_pred_test
* pred_test_restrict_list
* Does the "predicate inclusion test" for one conjunct of a predicate
* expression.
*/
static bool
one_pred_test(Expr *predicate, List *restrictinfo_list)
pred_test_restrict_list(Expr *predicate, List *restrictinfo_list)
{
List *item;
Assert(predicate != NULL);
foreach(item, restrictinfo_list)
{
RestrictInfo *restrictinfo = (RestrictInfo *) lfirst(item);
/* if any clause implies the predicate, return true */
if (one_pred_clause_expr_test(predicate,
(Node *) restrictinfo->clause))
if (pred_test_recurse_clause(predicate,
(Node *) restrictinfo->clause))
return true;
}
return false;
@ -1033,25 +1025,25 @@ one_pred_test(Expr *predicate, List *restrictinfo_list)
/*
* one_pred_clause_expr_test
* pred_test_recurse_clause
* Does the "predicate inclusion test" for a general restriction-clause
* expression.
* expression. Here we recursively deal with the possibility that the
* restriction clause is itself an AND or OR structure.
*/
static bool
one_pred_clause_expr_test(Expr *predicate, Node *clause)
pred_test_recurse_clause(Expr *predicate, Node *clause)
{
List *items,
*item;
if (is_opclause(clause))
return one_pred_clause_test(predicate, clause);
else if (or_clause(clause))
Assert(clause != NULL);
if (or_clause(clause))
{
items = ((Expr *) clause)->args;
foreach(item, items)
{
/* if any OR item doesn't imply the predicate, clause doesn't */
if (!one_pred_clause_expr_test(predicate, lfirst(item)))
if (!pred_test_recurse_clause(predicate, lfirst(item)))
return false;
}
return true;
@ -1065,39 +1057,37 @@ one_pred_clause_expr_test(Expr *predicate, Node *clause)
* if any AND item implies the predicate, the whole clause
* does
*/
if (one_pred_clause_expr_test(predicate, lfirst(item)))
if (pred_test_recurse_clause(predicate, lfirst(item)))
return true;
}
return false;
}
else
{
/* unknown clause type never implies the predicate */
return false;
}
return pred_test_recurse_pred(predicate, clause);
}
/*
* one_pred_clause_test
* pred_test_recurse_pred
* Does the "predicate inclusion test" for one conjunct of a predicate
* expression for a simple restriction clause.
* expression for a simple restriction clause. Here we recursively deal
* with the possibility that the predicate conjunct is itself an AND or
* OR structure.
*/
static bool
one_pred_clause_test(Expr *predicate, Node *clause)
pred_test_recurse_pred(Expr *predicate, Node *clause)
{
List *items,
*item;
if (is_opclause((Node *) predicate))
return clause_pred_clause_test(predicate, clause);
else if (or_clause((Node *) predicate))
Assert(predicate != NULL);
if (or_clause((Node *) predicate))
{
items = predicate->args;
foreach(item, items)
{
/* if any item is implied, the whole predicate is implied */
if (one_pred_clause_test(lfirst(item), clause))
if (pred_test_recurse_pred(lfirst(item), clause))
return true;
}
return false;
@ -1111,16 +1101,13 @@ one_pred_clause_test(Expr *predicate, Node *clause)
* if any item is not implied, the whole predicate is not
* implied
*/
if (!one_pred_clause_test(lfirst(item), clause))
if (!pred_test_recurse_pred(lfirst(item), clause))
return false;
}
return true;
}
else
{
elog(DEBUG, "Unsupported predicate type, index will not be used");
return false;
}
return pred_test_simple_clause(predicate, clause);
}
@ -1156,17 +1143,26 @@ static const StrategyNumber
/*
* clause_pred_clause_test
* Use operator class info to check whether clause implies predicate.
*
* pred_test_simple_clause
* Does the "predicate inclusion test" for a "simple clause" predicate
* for a single "simple clause" restriction. Currently, this only handles
* (binary boolean) operators that are in some btree operator class.
* and a "simple clause" restriction.
*
* We have two strategies for determining whether one simple clause
* implies another. A simple and general way is to see if they are
* equal(); this works for any kind of expression. (Actually, there
* is an implied assumption that the functions in the expression are
* cachable, ie dependent only on their input arguments --- but this
* was checked for the predicate by CheckPredicate().)
*
* Our other way works only for (binary boolean) operators that are
* in some btree operator class. We use the above operator implication
* table to be able to derive implications between nonidentical clauses.
*
* Eventually, rtree operators could also be handled by defining an
* appropriate "RT_implic_table" array.
*/
static bool
clause_pred_clause_test(Expr *predicate, Node *clause)
pred_test_simple_clause(Expr *predicate, Node *clause)
{
Var *pred_var,
*clause_var;
@ -1190,13 +1186,21 @@ clause_pred_clause_test(Expr *predicate, Node *clause)
Form_pg_amop aform;
ExprContext *econtext;
/* Check the basic form; for now, only allow the simplest case */
/* Note caller already verified is_opclause(predicate) */
if (!is_opclause(clause))
return false;
/* First try the equal() test */
if (equal((Node *) predicate, clause))
return true;
/*
* Can't do anything more unless they are both binary opclauses with
* a Var on the left and a Const on the right.
*/
if (!is_opclause((Node *) predicate))
return false;
pred_var = (Var *) get_leftop(predicate);
pred_const = (Const *) get_rightop(predicate);
if (!is_opclause(clause))
return false;
clause_var = (Var *) get_leftop((Expr *) clause);
clause_const = (Const *) get_rightop((Expr *) clause);
@ -1212,7 +1216,8 @@ clause_pred_clause_test(Expr *predicate, Node *clause)
* The implication can't be determined unless the predicate and the
* clause refer to the same attribute.
*/
if (clause_var->varattno != pred_var->varattno)
if (clause_var->varno != pred_var->varno ||
clause_var->varattno != pred_var->varattno)
return false;
/* Get the operators for the two clauses we're comparing */
@ -1250,15 +1255,16 @@ clause_pred_clause_test(Expr *predicate, Node *clause)
tuple = heap_getnext(scan, 0);
if (!HeapTupleIsValid(tuple))
{
elog(DEBUG, "clause_pred_clause_test: unknown pred_op");
/* predicate operator isn't btree-indexable */
heap_endscan(scan);
heap_close(relation, AccessShareLock);
return false;
}
aform = (Form_pg_amop) GETSTRUCT(tuple);
/* Get the predicate operator's strategy number (1 to 5) */
/* Get the predicate operator's btree strategy number (1 to 5) */
pred_strategy = (StrategyNumber) aform->amopstrategy;
Assert(pred_strategy >= 1 && pred_strategy <= 5);
/* Remember which operator class this strategy number came from */
opclass_id = aform->amopclaid;
@ -1282,7 +1288,7 @@ clause_pred_clause_test(Expr *predicate, Node *clause)
tuple = heap_getnext(scan, 0);
if (!HeapTupleIsValid(tuple))
{
elog(DEBUG, "clause_pred_clause_test: unknown clause_op");
/* clause operator isn't btree-indexable, or isn't in this opclass */
heap_endscan(scan);
heap_close(relation, AccessShareLock);
return false;
@ -1291,6 +1297,7 @@ clause_pred_clause_test(Expr *predicate, Node *clause)
/* Get the restriction clause operator's strategy number (1 to 5) */
clause_strategy = (StrategyNumber) aform->amopstrategy;
Assert(clause_strategy >= 1 && clause_strategy <= 5);
heap_endscan(scan);
@ -1316,7 +1323,8 @@ clause_pred_clause_test(Expr *predicate, Node *clause)
tuple = heap_getnext(scan, 0);
if (!HeapTupleIsValid(tuple))
{
elog(DEBUG, "clause_pred_clause_test: unknown test_op");
/* this probably shouldn't fail? */
elog(DEBUG, "pred_test_simple_clause: unknown test_op");
heap_endscan(scan);
heap_close(relation, AccessShareLock);
return false;
@ -1342,12 +1350,13 @@ clause_pred_clause_test(Expr *predicate, Node *clause)
(Var *) pred_const);
econtext = MakeExprContext(NULL, TransactionCommandContext);
test_result = ExecEvalExpr((Node *) test_expr, econtext, &isNull, NULL);
test_result = ExecEvalExprSwitchContext((Node *) test_expr, econtext,
&isNull, NULL);
FreeExprContext(econtext);
if (isNull)
{
elog(DEBUG, "clause_pred_clause_test: null test result");
elog(DEBUG, "pred_test_simple_clause: null test result");
return false;
}
return DatumGetBool(test_result);