plan: prune columns for LogicalTableDual (#7725)

pingcap · Sep 17, 2018 · 44e0578 · 44e0578
1 parent d47e303
commit 44e0578
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Showing 4 changed files with 19 additions and 6 deletions.
diff --git a/cmd/explaintest/r/explain_easy_stats.result b/cmd/explaintest/r/explain_easy_stats.result
@@ -92,8 +92,7 @@ TableReader_7	0.50	root	data:Selection_6
   └─TableScan_5	1.00	cop	table:t1, range:[1,1], keep order:false
 explain select c1 from t1 where c1 in (select c2 from t2);
 id	count	task	operator info
-Projection_10	0.00	root	test.t1.c1
-└─TableDual_11	0.00	root	rows:0
+TableDual_11	0.00	root	rows:0
 explain select * from information_schema.columns;
 id	count	task	operator info
 MemTableScan_4	10000.00	root	

diff --git a/plan/cbo_test.go b/plan/cbo_test.go
@@ -144,8 +144,7 @@ func (s *testAnalyzeSuite) TestTableDual(c *C) {
 	c.Assert(h.Update(dom.InfoSchema()), IsNil)
 
 	testKit.MustQuery(`explain select * from t where 1 = 0`).Check(testkit.Rows(
-		`Projection_5 0.00 root test.t.a`,
-		`└─TableDual_6 0.00 root rows:0`,
+		`TableDual_6 0.00 root rows:0`,
 	))
 
 	testKit.MustQuery(`explain select * from t where 1 = 1 limit 0`).Check(testkit.Rows(

diff --git a/plan/physical_plan_test.go b/plan/physical_plan_test.go
@@ -1124,7 +1124,7 @@ func (s *testPlanSuite) TestRefine(c *C) {
 		},
 		{
 			sql:  `select a from t where c = 1.9 and d > 3`,
-			best: "Dual->Projection",
+			best: "Dual",
 		},
 		{
 			sql:  `select a from t where c < 1.1`,
@@ -1144,7 +1144,7 @@ func (s *testPlanSuite) TestRefine(c *C) {
 		},
 		{
 			sql:  `select a from t where c = 123456789098765432101234`,
-			best: "Dual->Projection",
+			best: "Dual",
 		},
 		{
 			sql:  `select a from t where c = 'hanfei'`,

diff --git a/plan/rule_column_pruning.go b/plan/rule_column_pruning.go
@@ -164,6 +164,21 @@ func (ds *DataSource) PruneColumns(parentUsedCols []*expression.Column) {
 	}
 }
 
+// PruneColumns implements LogicalPlan interface.
+func (p *LogicalTableDual) PruneColumns(parentUsedCols []*expression.Column) {
+	used := getUsedList(parentUsedCols, p.schema)
+	for i := len(used) - 1; i >= 0; i-- {
+		if !used[i] {
+			p.schema.Columns = append(p.schema.Columns[:i], p.schema.Columns[i+1:]...)
+		}
+	}
+	for k, cols := range p.schema.TblID2Handle {
+		if p.schema.ColumnIndex(cols[0]) == -1 {
+			delete(p.schema.TblID2Handle, k)
+		}
+	}
+}
+
 func (p *LogicalJoin) extractUsedCols(parentUsedCols []*expression.Column) (leftCols []*expression.Column, rightCols []*expression.Column) {
 	for _, eqCond := range p.EqualConditions {
 		parentUsedCols = append(parentUsedCols, expression.ExtractColumns(eqCond)...)