planner: fix bug when pruning columns for TableDual (#11054) (#11247)

pingcap · Jul 15, 2019 · c705020 · c705020
1 parent 36f9978
commit c705020
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Showing 2 changed files with 11 additions and 1 deletion.
diff --git a/executor/executor_test.go b/executor/executor_test.go
@@ -1853,6 +1853,9 @@ func (s *testSuite) TestTableDual(c *C) {
 	result.Check(testkit.Rows("1"))
 	result = tk.MustQuery("Select 1 from dual where 1")
 	result.Check(testkit.Rows("1"))
+
+	tk.MustExec("create table t(a int primary key)")
+	tk.MustQuery("select t1.* from t t1, t t2 where t1.a=t2.a and 1=0").Check(testkit.Rows())
 }
 
 func (s *testSuite) TestTableScan(c *C) {

diff --git a/planner/core/rule_column_pruning.go b/planner/core/rule_column_pruning.go
@@ -262,8 +262,15 @@ func (p *LogicalTableDual) PruneColumns(parentUsedCols []*expression.Column) err
 		}
 	}
 	for k, cols := range p.schema.TblID2Handle {
-		if p.schema.ColumnIndex(cols[0]) == -1 {
+		for i := len(cols) - 1; i >= 0; i-- {
+			if p.schema.ColumnIndex(cols[i]) == -1 {
+				cols = append(cols[:i], cols[i+1:]...)
+			}
+		}
+		if len(cols) == 0 {
 			delete(p.schema.TblID2Handle, k)
+		} else {
+			p.schema.TblID2Handle[k] = cols
 		}
 	}
 	return nil