SQL optimization

Offering: openGaussDev

More detail: support null_test short circuit

# Conflicts:
#	src/test/regress/parallel_schedule0

Match-id-b136e3ec8a8b1f7983c92aa6c68b395a2ea6bbd7

src/gausskernel/optimizer/plan/createplan.cpp

@@ -222,6 +222,8 @@ static bool relIsDeltaNode(PlannerInfo* root, RelOptInfo* relOptInfo);
 
 static void ModifyWorktableWtParam(Node* planNode, int oldWtParam, int newWtParam);
 
+static bool ScanQualsViolateNotNullConstr(PlannerInfo* root, RelOptInfo* rel, Path* best_path);
+
 #define SATISFY_INFORMATIONAL_CONSTRAINT(joinPlan, joinType)                                                    \
     (u_sess->attr.attr_sql.enable_constraint_optimization && true == innerPlan((joinPlan))->hasUniqueResults && \
         JOIN_SEMI != (joinType) && JOIN_ANTI != (joinType))
@@ -752,11 +754,49 @@ static Plan* create_scan_plan(PlannerInfo* root, Path* best_path)
      */
     if (root->hasPseudoConstantQuals) {
         plan = create_gating_plan(root, plan, scan_clauses);
+    } else if (ScanQualsViolateNotNullConstr(root, rel, best_path)) {
+        /*
+        * If there is IS NULL qual on a known NOT-NULL attribute, insert a Result node to prevent needless execution.
+        */
+        plan = (Plan*)make_result(root, plan->targetlist, (Node*)list_make1(makeBoolConst(false, false)), plan);
     }
 
     return plan;
 }
 
+static bool IsScanPath(NodeTag type)
+{
+    return (
+        type == T_CStoreScan || type == T_CStoreIndexScan || type == T_CStoreIndexHeapScan || type == T_SeqScan ||
+        type == T_DfsScan || type == T_IndexScan || type == T_IndexOnlyScan || type == T_BitmapHeapScan
+    );
+}
+
+static bool ScanQualsViolateNotNullConstr(PlannerInfo* root, RelOptInfo* rel, Path* best_path)
+{
+    /* For now, we only support table scan optimization */
+    if (rel->rtekind != RTE_RELATION || !IsScanPath(best_path->pathtype)) {
+        return false;
+    }
+
+    List* scan_clauses = rel->baserestrictinfo;
+    ListCell* lc = NULL;
+    foreach (lc, scan_clauses) {
+        Node* clause = (Node*)lfirst(lc);
+        if (IsA(clause, RestrictInfo) && IsA(((RestrictInfo*)clause)->clause, NullTest)) {
+            NullTest* expr = (NullTest*)((RestrictInfo*)clause)->clause;
+            /* For attribute with NOT-NULL constraint, IS-NULL expression can be short-circuited */
+            if (expr->nulltesttype != IS_NULL || !IsA(expr->arg, Var)) {
+                continue;
+            }
+            if (check_var_nonnullable(root->parse, (Node*)expr->arg)) {
+                return true;
+            }
+        }
+    }
+    return false;
+}
+
 /*
  * Build a target list (ie, a list of TargetEntry) for a relation.
  */

src/test/regress/expected/null_test_opt.out

@@ -0,0 +1,100 @@
+create schema null_test_opt_nsp;
+set search_path = null_test_opt_nsp;
+create table t(a int, b int not null);
+insert into t values(1, 1);
+explain (costs off) select * from t where b is null order by 1, 2;
+            QUERY PLAN             
+-----------------------------------
+ Sort
+   Sort Key: a, b
+   ->  Result
+         One-Time Filter: false
+         ->  Seq Scan on t
+               Filter: (b IS NULL)
+(6 rows)
+
+select * from t where b is null order by 1, 2;
+ a | b 
+---+---
+(0 rows)
+
+explain (costs off) select * from t where b is not null order by 1, 2;
+     QUERY PLAN      
+---------------------
+ Sort
+   Sort Key: a, b
+   ->  Seq Scan on t
+(3 rows)
+
+select * from t where b is not null order by 1, 2;
+ a | b 
+---+---
+ 1 | 1
+(1 row)
+
+explain (costs off) select * from t where b is null or b is not null order by 1, 2;
+     QUERY PLAN      
+---------------------
+ Sort
+   Sort Key: a, b
+   ->  Seq Scan on t
+(3 rows)
+
+select * from t where b is null or b is not null order by 1, 2;
+ a | b 
+---+---
+ 1 | 1
+(1 row)
+
+explain (costs off) select * from t where b is null or a = 1 order by 1, 2;
+                QUERY PLAN                
+------------------------------------------
+ Sort
+   Sort Key: a, b
+   ->  Seq Scan on t
+         Filter: ((b IS NULL) OR (a = 1))
+(4 rows)
+
+select * from t where b is null or a = 1 order by 1, 2;
+ a | b 
+---+---
+ 1 | 1
+(1 row)
+
+explain (costs off) select * from t where b is null and a = 1 order by 1, 2;
+                   QUERY PLAN                    
+-------------------------------------------------
+ Sort
+   Sort Key: b
+   ->  Result
+         One-Time Filter: false
+         ->  Seq Scan on t
+               Filter: ((b IS NULL) AND (a = 1))
+(6 rows)
+
+select * from t where b is null and a = 1 order by 1, 2;
+ a | b 
+---+---
+(0 rows)
+
+explain (costs off) select * from t tt1 join t tt2 on tt1.a = tt2.b where tt1.a is null;
+               QUERY PLAN                
+-----------------------------------------
+ Hash Join
+   Hash Cond: (tt1.a = tt2.b)
+   ->  Seq Scan on t tt1
+         Filter: (a IS NULL)
+   ->  Hash
+         ->  Result
+               One-Time Filter: false
+               ->  Seq Scan on t tt2
+                     Filter: (b IS NULL)
+(9 rows)
+
+select * from t tt1 join t tt2 on tt1.a = tt2.b where tt1.a is null;
+ a | b | a | b 
+---+---+---+---
+(0 rows)
+
+drop schema null_test_opt_nsp cascade;
+NOTICE:  drop cascades to table t

src/test/regress/parallel_schedule0

@@ -25,8 +25,8 @@ test: pldeveloper_gs_source
 test: index_advisor
 test: pl_debugger_server pl_debugger_client
 test: update_for_wait_s1 update_for_wait_s2
-test: plan_hint plan_hint_set plan_hint_no_expand plan_hint_iud
-test: large_sequence int16 gs_dump_sequence
+test: plan_hint plan_hint_set plan_hint_no_expand plan_hint_iud null_test_opt
+test: large_sequence int16 forall_save_exceptions gs_dump_sequence
 test: gs_dump_tableof
 test: analyze_commands
 #test: single_node_job

src/test/regress/sql/null_test_opt.sql

@@ -0,0 +1,33 @@
+create schema null_test_opt_nsp;
+
+set search_path = null_test_opt_nsp;
+
+create table t(a int, b int not null);
+
+insert into t values(1, 1);
+
+explain (costs off) select * from t where b is null order by 1, 2;
+
+select * from t where b is null order by 1, 2;
+
+explain (costs off) select * from t where b is not null order by 1, 2;
+
+select * from t where b is not null order by 1, 2;
+
+explain (costs off) select * from t where b is null or b is not null order by 1, 2;
+
+select * from t where b is null or b is not null order by 1, 2;
+
+explain (costs off) select * from t where b is null or a = 1 order by 1, 2;
+
+select * from t where b is null or a = 1 order by 1, 2;
+
+explain (costs off) select * from t where b is null and a = 1 order by 1, 2;
+
+select * from t where b is null and a = 1 order by 1, 2;
+
+explain (costs off) select * from t tt1 join t tt2 on tt1.a = tt2.b where tt1.a is null;
+
+select * from t tt1 join t tt2 on tt1.a = tt2.b where tt1.a is null;
+
+drop schema null_test_opt_nsp cascade;