*
*
* IDENTIFICATION
- * $PostgreSQL: pgsql/src/backend/optimizer/path/indxpath.c,v 1.155 2004/01/05 23:39:54 tgl Exp $
+ * $PostgreSQL: pgsql/src/backend/optimizer/path/indxpath.c,v 1.156 2004/01/07 22:02:48 tgl Exp $
*
*-------------------------------------------------------------------------
*/
/*
* Define an "operator implication table" for btree operators ("strategies").
- * The "strategy numbers" are: (1) < (2) <= (3) = (4) >= (5) >
+ *
+ * The strategy numbers defined by btree indexes (see access/skey.h) are:
+ * (1) < (2) <= (3) = (4) >= (5) >
+ * and in addition we use (6) to represent <>. <> is not a btree-indexable
+ * operator, but we assume here that if the equality operator of a btree
+ * opclass has a negator operator, the negator behaves as <> for the opclass.
*
* The interpretation of:
*
* test_op = BT_implic_table[given_op-1][target_op-1]
*
- * where test_op, given_op and target_op are strategy numbers (from 1 to 5)
+ * where test_op, given_op and target_op are strategy numbers (from 1 to 6)
* of btree operators, is as follows:
*
* If you know, for some ATTR, that "ATTR given_op CONST1" is true, and you
* then the target expression must be true; if the test returns false, then
* the target expression may be false.
*
- * An entry where test_op==0 means the implication cannot be determined, i.e.,
- * this test should always be considered false.
+ * An entry where test_op == 0 means the implication cannot be determined,
+ * i.e., this test should always be considered false.
*/
+#define BTLT BTLessStrategyNumber
+#define BTLE BTLessEqualStrategyNumber
+#define BTEQ BTEqualStrategyNumber
+#define BTGE BTGreaterEqualStrategyNumber
+#define BTGT BTGreaterStrategyNumber
+#define BTNE 6
+
static const StrategyNumber
- BT_implic_table[BTMaxStrategyNumber][BTMaxStrategyNumber] = {
- {4, 4, 0, 0, 0},
- {5, 4, 0, 0, 0},
- {5, 4, 3, 2, 1},
- {0, 0, 0, 2, 1},
- {0, 0, 0, 2, 2}
+ BT_implic_table[6][6] = {
+/*
+ * The target operator:
+ *
+ * LT LE EQ GE GT NE
+ */
+ {BTGE, BTGE, 0, 0, 0, BTGE}, /* LT */
+ {BTGT, BTGE, 0, 0, 0, BTGT}, /* LE */
+ {BTGT, BTGE, BTEQ, BTLE, BTLT, BTNE}, /* EQ */
+ { 0, 0, 0, BTLE, BTLT, BTLT}, /* GE */
+ { 0, 0, 0, BTLE, BTLE, BTLE}, /* GT */
+ { 0, 0, 0, 0, 0, BTEQ} /* NE */
};
static bool
pred_test_simple_clause(Expr *predicate, Node *clause)
{
- Var *pred_var,
+ Node *leftop,
+ *rightop;
+ Node *pred_var,
*clause_var;
Const *pred_const,
*clause_const;
+ bool pred_var_on_left,
+ clause_var_on_left,
+ pred_op_negated;
Oid pred_op,
clause_op,
+ pred_op_negator,
+ clause_op_negator,
test_op = InvalidOid;
Oid opclass_id;
bool found = false;
/*
* Can't do anything more unless they are both binary opclauses with a
- * Var on the left and a Const on the right. (XXX someday try to
- * commute Const/Var cases?) Note we don't have to think about binary
- * relabeling of the Const node, since that would have been folded right
- * into the Const.
+ * Const on one side, and identical subexpressions on the other sides.
+ * Note we don't have to think about binary relabeling of the Const node,
+ * since that would have been folded right into the Const.
+ *
+ * If either Const is null, we also fail right away; this assumes that
+ * the test operator will always be strict.
*/
if (!is_opclause(predicate))
return false;
- pred_var = (Var *) get_leftop(predicate);
- pred_const = (Const *) get_rightop(predicate);
+ leftop = get_leftop(predicate);
+ rightop = get_rightop(predicate);
+ if (rightop == NULL)
+ return false; /* not a binary opclause */
+ if (IsA(rightop, Const))
+ {
+ pred_var = leftop;
+ pred_const = (Const *) rightop;
+ pred_var_on_left = true;
+ }
+ else if (IsA(leftop, Const))
+ {
+ pred_var = rightop;
+ pred_const = (Const *) leftop;
+ pred_var_on_left = false;
+ }
+ else
+ return false; /* no Const to be found */
+ if (pred_const->constisnull)
+ return false;
if (!is_opclause(clause))
return false;
- clause_var = (Var *) get_leftop((Expr *) clause);
- clause_const = (Const *) get_rightop((Expr *) clause);
-
- if (!IsA(clause_var, Var) ||
- clause_const == NULL ||
- !IsA(clause_const, Const) ||
- !IsA(pred_var, Var) ||
- pred_const == NULL ||
- !IsA(pred_const, Const))
+ leftop = get_leftop((Expr *) clause);
+ rightop = get_rightop((Expr *) clause);
+ if (rightop == NULL)
+ return false; /* not a binary opclause */
+ if (IsA(rightop, Const))
+ {
+ clause_var = leftop;
+ clause_const = (Const *) rightop;
+ clause_var_on_left = true;
+ }
+ else if (IsA(leftop, Const))
+ {
+ clause_var = rightop;
+ clause_const = (Const *) leftop;
+ clause_var_on_left = false;
+ }
+ else
+ return false; /* no Const to be found */
+ if (clause_const->constisnull)
return false;
/*
- * The implication can't be determined unless the predicate and the
- * clause refer to the same attribute.
+ * Check for matching subexpressions on the non-Const sides. We used to
+ * only allow a simple Var, but it's about as easy to allow any
+ * expression. Remember we already know that the pred expression does
+ * not contain any non-immutable functions, so identical expressions
+ * should yield identical results.
*/
- if (clause_var->varno != pred_var->varno ||
- clause_var->varattno != pred_var->varattno)
+ if (!equal(pred_var, clause_var))
return false;
- /* Get the operators for the two clauses we're comparing */
+ /*
+ * Okay, get the operators in the two clauses we're comparing.
+ * Commute them if needed so that we can assume the variables are
+ * on the left.
+ */
pred_op = ((OpExpr *) predicate)->opno;
+ if (!pred_var_on_left)
+ {
+ pred_op = get_commutator(pred_op);
+ if (!OidIsValid(pred_op))
+ return false;
+ }
+
clause_op = ((OpExpr *) clause)->opno;
+ if (!clause_var_on_left)
+ {
+ clause_op = get_commutator(clause_op);
+ if (!OidIsValid(clause_op))
+ return false;
+ }
/*
* Try to find a btree opclass containing the needed operators.
ObjectIdGetDatum(pred_op),
0, 0, 0);
+ /*
+ * If we couldn't find any opclass containing the pred_op, perhaps it
+ * is a <> operator. See if it has a negator that is in an opclass.
+ */
+ pred_op_negated = false;
+ if (catlist->n_members == 0)
+ {
+ pred_op_negator = get_negator(pred_op);
+ if (OidIsValid(pred_op_negator))
+ {
+ pred_op_negated = true;
+ ReleaseSysCacheList(catlist);
+ catlist = SearchSysCacheList(AMOPOPID, 1,
+ ObjectIdGetDatum(pred_op_negator),
+ 0, 0, 0);
+ }
+ }
+
+ /* Also may need the clause_op's negator */
+ clause_op_negator = get_negator(clause_op);
+
+ /* Now search the opclasses */
for (i = 0; i < catlist->n_members; i++)
{
HeapTuple pred_tuple = &catlist->members[i]->tuple;
pred_strategy = (StrategyNumber) pred_form->amopstrategy;
Assert(pred_strategy >= 1 && pred_strategy <= 5);
+ if (pred_op_negated)
+ {
+ /* Only consider negators that are = */
+ if (pred_strategy != BTEqualStrategyNumber)
+ continue;
+ pred_strategy = BTNE;
+ }
+
/*
* From the same opclass, find a strategy number for the clause_op,
* if possible
clause_strategy = (StrategyNumber) clause_form->amopstrategy;
Assert(clause_strategy >= 1 && clause_strategy <= 5);
clause_subtype = clause_form->amopsubtype;
-
- /* done with clause_tuple */
ReleaseSysCache(clause_tuple);
-
- /*
- * Look up the "test" strategy number in the implication table
- */
- test_strategy = BT_implic_table[clause_strategy - 1][pred_strategy - 1];
- if (test_strategy == 0)
+ }
+ else if (OidIsValid(clause_op_negator))
+ {
+ clause_tuple = SearchSysCache(AMOPOPID,
+ ObjectIdGetDatum(clause_op_negator),
+ ObjectIdGetDatum(opclass_id),
+ 0, 0);
+ if (HeapTupleIsValid(clause_tuple))
{
- /* Can't determine implication using this interpretation */
- continue;
+ Form_pg_amop clause_form = (Form_pg_amop) GETSTRUCT(clause_tuple);
+
+ /* Get the restriction clause operator's strategy/subtype */
+ clause_strategy = (StrategyNumber) clause_form->amopstrategy;
+ Assert(clause_strategy >= 1 && clause_strategy <= 5);
+ clause_subtype = clause_form->amopsubtype;
+ ReleaseSysCache(clause_tuple);
+
+ /* Only consider negators that are = */
+ if (clause_strategy != BTEqualStrategyNumber)
+ continue;
+ clause_strategy = BTNE;
}
+ else
+ continue;
+ }
+ else
+ continue;
- /*
- * See if opclass has an operator for the test strategy and the
- * clause datatype.
- */
+ /*
+ * Look up the "test" strategy number in the implication table
+ */
+ test_strategy = BT_implic_table[clause_strategy - 1][pred_strategy - 1];
+ if (test_strategy == 0)
+ {
+ /* Can't determine implication using this interpretation */
+ continue;
+ }
+
+ /*
+ * See if opclass has an operator for the test strategy and the
+ * clause datatype.
+ */
+ if (test_strategy == BTNE)
+ {
test_op = get_opclass_member(opclass_id, clause_subtype,
- test_strategy);
+ BTEqualStrategyNumber);
if (OidIsValid(test_op))
- {
- found = true;
- break;
- }
+ test_op = get_negator(test_op);
+ }
+ else
+ {
+ test_op = get_opclass_member(opclass_id, clause_subtype,
+ test_strategy);
+ }
+ if (OidIsValid(test_op))
+ {
+ found = true;
+ break;
}
}
/* And execute it. */
test_result = ExecEvalExprSwitchContext(test_exprstate,
- GetPerTupleExprContext(estate),
+ GetPerTupleExprContext(estate),
&isNull, NULL);
/* Get back to outer memory context */
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