infoschema: fix load drop database schema bug and refine db-table api error.

infoschema/builder.go

@@ -154,22 +154,22 @@ func (b *Builder) applyDropSchema(schemaID int64) []int64 {
 	delete(b.is.schemaMap, di.Name.L)
 
 	// Copy the sortedTables that contain the table we are going to drop.
+	tableIDs := make([]int64, 0, len(di.Tables))
 	bucketIdxMap := make(map[int]struct{})
 	for _, tbl := range di.Tables {
 		bucketIdxMap[tableBucketIdx(tbl.ID)] = struct{}{}
+		// TODO: If the table ID doesn't exist.
+		tableIDs = append(tableIDs, tbl.ID)
 	}
 	for bucketIdx := range bucketIdxMap {
 		b.copySortedTablesBucket(bucketIdx)
 	}
 
-	ids := make([]int64, 0, len(di.Tables))
 	di = di.Clone()
-	for _, tbl := range di.Tables {
-		b.applyDropTable(di, tbl.ID)
-		// TODO: If the table ID doesn't exist.
-		ids = append(ids, tbl.ID)
+	for _, id := range tableIDs {
+		b.applyDropTable(di, id)
 	}
-	return ids
+	return tableIDs
 }
 
 func (b *Builder) copySortedTablesBucket(bucketIdx int) {

infoschema/tables_test.go

@@ -22,7 +22,9 @@ import (
 
 	. "github.com/pingcap/check"
 	"github.com/pingcap/parser/auth"
+	"github.com/pingcap/parser/model"
 	"github.com/pingcap/parser/mysql"
+	"github.com/pingcap/parser/terror"
 	"github.com/pingcap/tidb/domain"
 	"github.com/pingcap/tidb/infoschema"
 	"github.com/pingcap/tidb/kv"
@@ -525,3 +527,21 @@ func (s *testTableSuite) TestColumnStatistics(c *C) {
 	tk := testkit.NewTestKit(c, s.store)
 	tk.MustQuery("select * from information_schema.column_statistics").Check(testkit.Rows())
 }
+
+func (s *testTableSuite) TestReloadDropDatabase(c *C) {
+	tk := testkit.NewTestKit(c, s.store)
+	tk.MustExec("create database test_dbs")
+	tk.MustExec("use test_dbs")
+	tk.MustExec("create table t1 (a int)")
+	tk.MustExec("create table t2 (a int)")
+	tk.MustExec("create table t3 (a int)")
+	is := domain.GetDomain(tk.Se).InfoSchema()
+	t2, err := is.TableByName(model.NewCIStr("test_dbs"), model.NewCIStr("t2"))
+	c.Assert(err, IsNil)
+	tk.MustExec("drop database test_dbs")
+	is = domain.GetDomain(tk.Se).InfoSchema()
+	_, err = is.TableByName(model.NewCIStr("test_dbs"), model.NewCIStr("t2"))
+	c.Assert(terror.ErrorEqual(infoschema.ErrTableNotExists, err), IsTrue)
+	_, ok := is.TableByID(t2.Meta().ID)
+	c.Assert(ok, IsFalse)
+}