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Optimize BooleanTest with non-nullable input
The BooleanTest construct (IS [NOT] TRUE/FALSE/UNKNOWN) treats a NULL input as the logical value "unknown". However, when the input is proven to be non-nullable, this special handling becomes redundant. In such cases, the construct can be simplified directly to a boolean expression or a constant. Author: Richard Guo <guofenglinux@gmail.com> Reviewed-by: Tender Wang <tndrwang@gmail.com> Discussion: https://postgr.es/m/CAMbWs49BMAOWvkdSHxpUDnniqJcEcGq3_8dd_5wTR4xrQY8urA@mail.gmail.com
This commit is contained in:
Richard Guo
parent
0a37961254
commit
0aaf0de7fe
3 changed files with 204 additions and 0 deletions
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@ -3686,6 +3686,9 @@ eval_const_expressions_mutator(Node *node,
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context);
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if (arg && IsA(arg, Const))
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{
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/*
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* If arg is Const, simplify to constant.
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*/
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Const *carg = (Const *) arg;
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bool result;
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@ -3722,6 +3725,34 @@ eval_const_expressions_mutator(Node *node,
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return makeBoolConst(result, false);
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}
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if (arg && expr_is_nonnullable(context->root, (Expr *) arg, false))
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{
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/*
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* If arg is proven non-nullable, simplify to boolean
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* expression or constant.
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*/
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switch (btest->booltesttype)
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{
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case IS_TRUE:
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case IS_NOT_FALSE:
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return arg;
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case IS_FALSE:
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case IS_NOT_TRUE:
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return (Node *) make_notclause((Expr *) arg);
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case IS_UNKNOWN:
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return makeBoolConst(false, false);
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case IS_NOT_UNKNOWN:
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return makeBoolConst(true, false);
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default:
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elog(ERROR, "unrecognized booltesttype: %d",
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(int) btest->booltesttype);
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break;
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}
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}
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newbtest = makeNode(BooleanTest);
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newbtest->arg = (Expr *) arg;
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@ -768,3 +768,122 @@ SELECT * FROM dist_tab t1 JOIN dist_tab t2 ON t1.val_nn IS NOT DISTINCT FROM t2.
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RESET enable_nestloop;
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DROP TABLE dist_tab;
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DROP TYPE dist_row_t;
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--
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-- Test optimization of BooleanTest (IS [NOT] TRUE/FALSE/UNKNOWN) on
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-- non-nullable input
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--
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CREATE TABLE bool_tab (id int, flag_nn boolean NOT NULL, flag_null boolean);
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INSERT INTO bool_tab VALUES (1, true, true);
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INSERT INTO bool_tab VALUES (2, false, NULL);
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CREATE INDEX bool_tab_nn_idx ON bool_tab (flag_nn);
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ANALYZE bool_tab;
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-- Ensure that the predicate folds to constant FALSE
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EXPLAIN (COSTS OFF)
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SELECT id FROM bool_tab WHERE flag_nn IS UNKNOWN;
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QUERY PLAN
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------------------------------
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Result
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Replaces: Scan on bool_tab
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One-Time Filter: false
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(3 rows)
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SELECT id FROM bool_tab WHERE flag_nn IS UNKNOWN;
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id
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----
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(0 rows)
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-- Ensure that the predicate folds to constant TRUE
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EXPLAIN (COSTS OFF)
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SELECT id FROM bool_tab WHERE flag_nn IS NOT UNKNOWN;
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QUERY PLAN
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----------------------
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Seq Scan on bool_tab
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(1 row)
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SELECT id FROM bool_tab WHERE flag_nn IS NOT UNKNOWN;
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id
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----
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1
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2
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(2 rows)
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-- Ensure that the predicate folds to flag_nn
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EXPLAIN (COSTS OFF)
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SELECT id FROM bool_tab WHERE flag_nn IS TRUE;
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QUERY PLAN
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----------------------
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Seq Scan on bool_tab
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Filter: flag_nn
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(2 rows)
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SELECT id FROM bool_tab WHERE flag_nn IS TRUE;
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id
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----
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1
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(1 row)
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-- Ensure that the predicate folds to flag_nn, and thus can use index scan
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SET enable_seqscan TO off;
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EXPLAIN (COSTS OFF)
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SELECT id FROM bool_tab WHERE flag_nn IS NOT FALSE;
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QUERY PLAN
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----------------------------------------------
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Index Scan using bool_tab_nn_idx on bool_tab
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Index Cond: (flag_nn = true)
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(2 rows)
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SELECT id FROM bool_tab WHERE flag_nn IS NOT FALSE;
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id
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----
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1
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(1 row)
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RESET enable_seqscan;
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-- Ensure that the predicate folds to not flag_nn
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EXPLAIN (COSTS OFF)
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SELECT id FROM bool_tab WHERE flag_nn IS FALSE;
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QUERY PLAN
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-------------------------
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Seq Scan on bool_tab
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Filter: (NOT flag_nn)
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(2 rows)
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SELECT id FROM bool_tab WHERE flag_nn IS FALSE;
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id
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----
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2
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(1 row)
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-- Ensure that the predicate folds to not flag_nn, and thus can use index scan
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SET enable_seqscan TO off;
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EXPLAIN (COSTS OFF)
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SELECT id FROM bool_tab WHERE flag_nn IS NOT TRUE;
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QUERY PLAN
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----------------------------------------------
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Index Scan using bool_tab_nn_idx on bool_tab
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Index Cond: (flag_nn = false)
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(2 rows)
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SELECT id FROM bool_tab WHERE flag_nn IS NOT TRUE;
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id
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----
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2
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(1 row)
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RESET enable_seqscan;
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-- Ensure that the predicate is preserved as a BooleanTest
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EXPLAIN (COSTS OFF)
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SELECT id FROM bool_tab WHERE flag_null IS UNKNOWN;
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QUERY PLAN
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----------------------------------
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Seq Scan on bool_tab
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Filter: (flag_null IS UNKNOWN)
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(2 rows)
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SELECT id FROM bool_tab WHERE flag_null IS UNKNOWN;
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id
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----
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2
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(1 row)
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DROP TABLE bool_tab;
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@ -369,3 +369,57 @@ RESET enable_nestloop;
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DROP TABLE dist_tab;
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DROP TYPE dist_row_t;
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--
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-- Test optimization of BooleanTest (IS [NOT] TRUE/FALSE/UNKNOWN) on
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-- non-nullable input
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--
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CREATE TABLE bool_tab (id int, flag_nn boolean NOT NULL, flag_null boolean);
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INSERT INTO bool_tab VALUES (1, true, true);
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INSERT INTO bool_tab VALUES (2, false, NULL);
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CREATE INDEX bool_tab_nn_idx ON bool_tab (flag_nn);
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ANALYZE bool_tab;
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-- Ensure that the predicate folds to constant FALSE
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EXPLAIN (COSTS OFF)
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SELECT id FROM bool_tab WHERE flag_nn IS UNKNOWN;
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SELECT id FROM bool_tab WHERE flag_nn IS UNKNOWN;
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-- Ensure that the predicate folds to constant TRUE
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EXPLAIN (COSTS OFF)
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SELECT id FROM bool_tab WHERE flag_nn IS NOT UNKNOWN;
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SELECT id FROM bool_tab WHERE flag_nn IS NOT UNKNOWN;
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-- Ensure that the predicate folds to flag_nn
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EXPLAIN (COSTS OFF)
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SELECT id FROM bool_tab WHERE flag_nn IS TRUE;
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SELECT id FROM bool_tab WHERE flag_nn IS TRUE;
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-- Ensure that the predicate folds to flag_nn, and thus can use index scan
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SET enable_seqscan TO off;
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EXPLAIN (COSTS OFF)
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SELECT id FROM bool_tab WHERE flag_nn IS NOT FALSE;
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SELECT id FROM bool_tab WHERE flag_nn IS NOT FALSE;
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RESET enable_seqscan;
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-- Ensure that the predicate folds to not flag_nn
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EXPLAIN (COSTS OFF)
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SELECT id FROM bool_tab WHERE flag_nn IS FALSE;
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SELECT id FROM bool_tab WHERE flag_nn IS FALSE;
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-- Ensure that the predicate folds to not flag_nn, and thus can use index scan
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SET enable_seqscan TO off;
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EXPLAIN (COSTS OFF)
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SELECT id FROM bool_tab WHERE flag_nn IS NOT TRUE;
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SELECT id FROM bool_tab WHERE flag_nn IS NOT TRUE;
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RESET enable_seqscan;
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-- Ensure that the predicate is preserved as a BooleanTest
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EXPLAIN (COSTS OFF)
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SELECT id FROM bool_tab WHERE flag_null IS UNKNOWN;
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SELECT id FROM bool_tab WHERE flag_null IS UNKNOWN;
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DROP TABLE bool_tab;
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