plan: fix panic caused by empty schema of LogicalTableDual (#7906)

* fix drop view if exist error (#7833)
pingcap · Oct 16, 2018 · de6b582 · de6b582
1 parent dcf3816
commit de6b582
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Showing 3 changed files with 11 additions and 1 deletion.
diff --git a/planner/core/logical_plan_test.go b/planner/core/logical_plan_test.go
@@ -1224,6 +1224,13 @@ func (s *testPlanSuite) TestColumnPruning(c *C) {
 				3: {"a"},
 			},
 		},
+		//issue 7833
+		{
+			sql: "drop view if exists v",
+			ans: map[int][]string{
+				1: {},
+			},
+		},
 	}
 	for _, tt := range tests {
 		comment := Commentf("for %s", tt.sql)

diff --git a/planner/core/planbuilder.go b/planner/core/planbuilder.go
@@ -227,6 +227,9 @@ func (b *PlanBuilder) buildDo(v *ast.DoStmt) (Plan, error) {
 			RetType:  expr.GetType(),
 		})
 	}
+	if dual.schema == nil {
+		dual.schema = expression.NewSchema()
+	}
 	p.SetChildren(dual)
 	p.self = p
 	p.SetSchema(schema)

diff --git a/planner/core/rule_column_pruning.go b/planner/core/rule_column_pruning.go
@@ -167,7 +167,7 @@ func (ds *DataSource) PruneColumns(parentUsedCols []*expression.Column) {
 
 // PruneColumns implements LogicalPlan interface.
 func (p *LogicalTableDual) PruneColumns(parentUsedCols []*expression.Column) {
-	used := getUsedList(parentUsedCols, p.schema)
+	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:]...)