Parser & query executor: support formalized ShowMigrations statement

go/vt/vttablet/onlineddl/executor.go

@@ -4693,6 +4693,31 @@ func (e *Executor) SubmitMigration(
 	return result, nil
 }
 
+// ShowMigrations shows migrations, optionally filtered by a condition
+func (e *Executor) ShowMigrations(ctx context.Context, show *sqlparser.Show) (result *sqltypes.Result, err error) {
+	if atomic.LoadInt64(&e.isOpen) == 0 {
+		return nil, vterrors.New(vtrpcpb.Code_FAILED_PRECONDITION, "online ddl is disabled")
+	}
+	showBasic, ok := show.Internal.(*sqlparser.ShowBasic)
+	if !ok {
+		return nil, vterrors.Errorf(vtrpcpb.Code_INTERNAL, "[BUG] ShowMigrations expects a ShowBasic statement. Got: %s", sqlparser.String(show))
+	}
+	if showBasic.Command != sqlparser.VitessMigrations {
+		return nil, vterrors.Errorf(vtrpcpb.Code_INTERNAL, "[BUG] ShowMigrations expects a VitessMigrations command, got %v. Statement: %s", sqlparser.VitessMigrations, sqlparser.String(show))
+	}
+	whereExpr := ""
+	if showBasic.Filter != nil {
+		if showBasic.Filter.Filter != nil {
+			whereExpr = fmt.Sprintf(" where %s", sqlparser.String(showBasic.Filter.Filter))
+		} else if showBasic.Filter.Like != "" {
+			lit := sqlparser.String(sqlparser.NewStrLiteral(showBasic.Filter.Like))
+			whereExpr = fmt.Sprintf(" where migration_uuid LIKE %s OR migration_context LIKE %s OR migration_status LIKE %s", lit, lit, lit)
+		}
+	}
+	query := sqlparser.BuildParsedQuery(sqlShowMigrationsWhere, whereExpr).Query
+	return e.execQuery(ctx, query)
+}
+
 // ShowMigrationLogs reads the migration log for a given migration
 func (e *Executor) ShowMigrationLogs(ctx context.Context, stmt *sqlparser.ShowMigrationLogs) (result *sqltypes.Result, err error) {
 	if atomic.LoadInt64(&e.isOpen) == 0 {

go/vt/vttablet/onlineddl/schema.go

@@ -359,6 +359,10 @@ const (
 			AND cleanup_timestamp IS NULL
 			AND completed_timestamp IS NULL
 	`
+	sqlShowMigrationsWhere = `SELECT *
+		FROM _vt.schema_migrations
+		%s
+	`
 	sqlSelectMigration = `SELECT
 			id,
 			migration_uuid,

go/vt/vttablet/tabletserver/planbuilder/builder.go

@@ -135,7 +135,10 @@ func analyzeInsert(ins *sqlparser.Insert, tables map[string]*schema.Table) (plan
 func analyzeShow(show *sqlparser.Show, dbName string) (plan *Plan, err error) {
 	switch showInternal := show.Internal.(type) {
 	case *sqlparser.ShowBasic:
-		if showInternal.Command == sqlparser.Table {
+		switch showInternal.Command {
+		case sqlparser.VitessMigrations:
+			return &Plan{PlanID: PlanShowMigrations, FullStmt: show}, nil
+		case sqlparser.Table:
 			// rewrite WHERE clause if it exists
 			// `where Tables_in_Keyspace` => `where Tables_in_DbName`
 			if showInternal.Filter != nil {

go/vt/vttablet/tabletserver/planbuilder/plan.go

@@ -76,6 +76,7 @@ const (
 	PlanCallProc
 	PlanAlterMigration
 	PlanRevertMigration
+	PlanShowMigrations
 	PlanShowMigrationLogs
 	PlanShowThrottledApps
 	PlanShowThrottlerStatus
@@ -112,6 +113,7 @@ var planName = []string{
 	"CallProcedure",
 	"AlterMigration",
 	"RevertMigration",
+	"ShowMigrations",
 	"ShowMigrationLogs",
 	"ShowThrottledApps",
 	"ShowThrottlerStatus",

go/vt/vttablet/tabletserver/query_executor.go

@@ -204,6 +204,8 @@ func (qre *QueryExecutor) Execute() (reply *sqltypes.Result, err error) {
 		return qre.execAlterMigration()
 	case p.PlanRevertMigration:
 		return qre.execRevertMigration()
+	case p.PlanShowMigrations:
+		return qre.execShowMigrations()
 	case p.PlanShowMigrationLogs:
 		return qre.execShowMigrationLogs()
 	case p.PlanShowThrottledApps:
@@ -1057,6 +1059,13 @@ func (qre *QueryExecutor) execRevertMigration() (*sqltypes.Result, error) {
 	return qre.tsv.onlineDDLExecutor.SubmitMigration(qre.ctx, qre.plan.FullStmt)
 }
 
+func (qre *QueryExecutor) execShowMigrations() (*sqltypes.Result, error) {
+	if showStmt, ok := qre.plan.FullStmt.(*sqlparser.Show); ok {
+		return qre.tsv.onlineDDLExecutor.ShowMigrations(qre.ctx, showStmt)
+	}
+	return nil, vterrors.New(vtrpcpb.Code_INTERNAL, "Expecting SHOW VITESS_MIGRATIONS plan")
+}
+
 func (qre *QueryExecutor) execShowMigrationLogs() (*sqltypes.Result, error) {
 	if showMigrationLogsStmt, ok := qre.plan.FullStmt.(*sqlparser.ShowMigrationLogs); ok {
 		return qre.tsv.onlineDDLExecutor.ShowMigrationLogs(qre.ctx, showMigrationLogsStmt)