added default database in 'show database'

Signed-off-by: akilan <Akilanselva@hotmail.com>

go/vt/sqlparser/ast_funcs.go

@@ -1243,6 +1243,8 @@ func (ty ShowCommandType) ToString() string {
 		return VariableGlobalStr
 	case VariableSession:
 		return VariableSessionStr
+	case Keyspace:
+		return KeyspaceStr
 	default:
 		return "Unknown ShowCommandType"
 	}

go/vt/sqlparser/constants.go

@@ -219,6 +219,7 @@ const (
 	StatusSessionStr   = " status"
 	VariableGlobalStr  = " global variables"
 	VariableSessionStr = " variables"
+	KeyspaceStr        = " keyspaces"
 
 	// DropKeyType strings
 	PrimaryKeyTypeStr = "primary key"
@@ -458,6 +459,7 @@ const (
 	StatusSession
 	VariableGlobal
 	VariableSession
+	Keyspace
 )
 
 // DropKeyType constants

go/vt/sqlparser/parse_test.go

@@ -1479,10 +1479,10 @@ var (
 		output: "show variables",
 	}, {
 		input:  "show vitess_keyspaces",
-		output: "show databases",
+		output: "show keyspaces",
 	}, {
 		input:  "show vitess_keyspaces like '%'",
-		output: "show databases like '%'",
+		output: "show keyspaces like '%'",
 	}, {
 		input: "show vitess_shards",
 	}, {

go/vt/sqlparser/sql.go

@@ -7753,13 +7753,13 @@ yydefault:
 		yyDollar = yyS[yypt-3 : yypt+1]
 //line sql.y:2346
 		{
-			yyVAL.statement = &Show{&ShowBasic{Command: Database, Filter: yyDollar[3].showFilter}}
+			yyVAL.statement = &Show{&ShowBasic{Command: Keyspace, Filter: yyDollar[3].showFilter}}
 		}
 	case 429:
 		yyDollar = yyS[yypt-3 : yypt+1]
 //line sql.y:2350
 		{
-			yyVAL.statement = &Show{&ShowBasic{Command: Database, Filter: yyDollar[3].showFilter}}
+			yyVAL.statement = &Show{&ShowBasic{Command: Keyspace, Filter: yyDollar[3].showFilter}}
 		}
 	case 430:
 		yyDollar = yyS[yypt-4 : yypt+1]

go/vt/sqlparser/sql.y

@@ -2344,11 +2344,11 @@ show_statement:
   }
 | SHOW KEYSPACES like_or_where_opt
   {
-    $$ = &Show{&ShowBasic{Command: Database, Filter: $3}}
+    $$ = &Show{&ShowBasic{Command: Keyspace, Filter: $3}}
   }
 | SHOW VITESS_KEYSPACES like_or_where_opt
   {
-    $$ = &Show{&ShowBasic{Command: Database, Filter: $3}}
+    $$ = &Show{&ShowBasic{Command: Keyspace, Filter: $3}}
   }
 | SHOW FUNCTION STATUS like_or_where_opt
   {

go/vt/vtgate/executor_test.go

@@ -437,11 +437,19 @@ func TestExecutorShow(t *testing.T) {
 	executor, _, _, sbclookup := createLegacyExecutorEnv()
 	session := NewSafeSession(&vtgatepb.Session{TargetString: "@master"})
 
-	for _, query := range []string{"show databases", "show vitess_keyspaces", "show keyspaces", "show DATABASES", "show schemas", "show SCHEMAS"} {
+	for _, query := range []string{"show vitess_keyspaces", "show keyspaces"} {
 		qr, err := executor.Execute(ctx, "TestExecute", session, query, nil)
 		require.NoError(t, err)
 		require.EqualValues(t, 5, qr.RowsAffected, fmt.Sprintf("unexpected results running query: %s", query))
 	}
+
+	for _, query := range []string{"show databases", "show DATABASES", "show schemas", "show SCHEMAS"} {
+		qr, err := executor.Execute(ctx, "TestExecute", session, query, nil)
+		require.NoError(t, err)
+		// Showing default tables (5+4[default])
+		require.EqualValues(t, 9, qr.RowsAffected, fmt.Sprintf("unexpected results running query: %s", query))
+	}
+
 	_, err := executor.Execute(ctx, "TestExecute", session, "show variables", nil)
 	require.NoError(t, err)
 	_, err = executor.Execute(ctx, "TestExecute", session, "show collation", nil)

go/vt/vtgate/planbuilder/show.go

@@ -57,7 +57,7 @@ func buildShowBasicPlan(show *sqlparser.ShowBasic, vschema ContextVSchema) (engi
 	case sqlparser.Collation, sqlparser.Function, sqlparser.Privilege, sqlparser.Procedure,
 		sqlparser.VariableGlobal, sqlparser.VariableSession:
 		return showSendAnywhere(show, vschema)
-	case sqlparser.Database:
+	case sqlparser.Database, sqlparser.Keyspace:
 		ks, err := vschema.AllKeyspace()
 		if err != nil {
 			return nil, err
@@ -73,7 +73,17 @@ func buildShowBasicPlan(show *sqlparser.ShowBasic, vschema ContextVSchema) (engi
 			filter = regexp.MustCompile(".*")
 		}
 
-		rows := make([][]sqltypes.Value, 0, len(ks))
+		//rows := make([][]sqltypes.Value, 0, len(ks)+4)
+		var rows [][]sqltypes.Value
+
+		if show.Command == sqlparser.Database {
+			//Hard code default databases
+			rows = append(rows, buildVarCharRow("information_schema"))
+			rows = append(rows, buildVarCharRow("mysql"))
+			rows = append(rows, buildVarCharRow("sys"))
+			rows = append(rows, buildVarCharRow("performance_schema"))
+		}
+
 		for _, v := range ks {
 			if filter.MatchString(v.Name) {
 				rows = append(rows, buildVarCharRow(v.Name))