[Backport 12.0]: Add planner-version flag to vtexplain

go/cmd/vtexplain/vtexplain.go

@@ -26,6 +26,8 @@ import (
 	"vitess.io/vitess/go/vt/logutil"
 	"vitess.io/vitess/go/vt/servenv"
 	"vitess.io/vitess/go/vt/vtexplain"
+
+	querypb "vitess.io/vitess/go/vt/proto/query"
 )
 
 var (
@@ -43,10 +45,12 @@ var (
 	normalize          = flag.Bool("normalize", false, "Whether to enable vtgate normalization")
 	outputMode         = flag.String("output-mode", "text", "Output in human-friendly text or json")
 	dbName             = flag.String("dbname", "", "Optional database target to override normal routing")
+	plannerVersionStr  = flag.String("planner-version", "V3", "Sets the query planner version to use when generating the explain output. Valid values are V3 and Gen4")
 
 	// vtexplainFlags lists all the flags that should show in usage
 	vtexplainFlags = []string{
 		"output-mode",
+		"planner-version",
 		"normalize",
 		"shards",
 		"replication-mode",
@@ -165,8 +169,14 @@ func parseAndRun() error {
 		return err
 	}
 
+	plannerVersion := querypb.ExecuteOptions_PlannerVersion(querypb.ExecuteOptions_PlannerVersion_value[*plannerVersionStr])
+	if plannerVersion != querypb.ExecuteOptions_V3 && plannerVersion != querypb.ExecuteOptions_Gen4 {
+		return fmt.Errorf("invalid value specified for planner-version of '%s' -- valid values are V3 and Gen4", *plannerVersionStr)
+	}
+
 	opts := &vtexplain.Options{
 		ExecutionMode:   *executionMode,
+		PlannerVersion:  plannerVersion,
 		ReplicationMode: *replicationMode,
 		NumShards:       *numShards,
 		Normalize:       *normalize,

go/vt/vtexplain/vtexplain.go

@@ -58,6 +58,9 @@ type Options struct {
 	// NumShards indicates the number of shards in the topology
 	NumShards int
 
+	// PlannerVersion indicates whether or not we should use the Gen4 planner
+	PlannerVersion querypb.ExecuteOptions_PlannerVersion
+
 	// ReplicationMode must be set to either "ROW" or "STATEMENT" before
 	// initialization
 	ReplicationMode string

go/vt/vtexplain/vtexplain_vtgate.go

@@ -38,6 +38,7 @@ import (
 	"vitess.io/vitess/go/vt/vtgate/engine"
 	"vitess.io/vitess/go/vt/vttablet/queryservice"
 
+	querypb "vitess.io/vitess/go/vt/proto/query"
 	topodatapb "vitess.io/vitess/go/vt/proto/topodata"
 	vschemapb "vitess.io/vitess/go/vt/proto/vschema"
 	vtgatepb "vitess.io/vitess/go/vt/proto/vtgate"
@@ -68,6 +69,13 @@ func initVtgateExecutor(vSchemaStr, ksShardMapStr string, opts *Options) error {
 
 	vtgateSession.TargetString = opts.Target
 
+	if opts.PlannerVersion != querypb.ExecuteOptions_DEFAULT_PLANNER {
+		if vtgateSession.Options == nil {
+			vtgateSession.Options = &querypb.ExecuteOptions{}
+		}
+		vtgateSession.Options.PlannerVersion = opts.PlannerVersion
+	}
+
 	streamSize := 10
 	var schemaTracker vtgate.SchemaInfo // no schema tracker for these tests
 	vtgateExecutor = vtgate.NewExecutor(context.Background(), explainTopo, vtexplainCell, resolver, opts.Normalize, false /*do not warn for sharded only*/, streamSize, cache.DefaultConfig, schemaTracker, false /*no-scatter*/)

go/vt/vtexplain/vtexplain_vttablet.go

@@ -506,11 +506,12 @@ func (t *explainTablet) HandleQuery(c *mysql.Conn, query string, callback func(*
 			return fmt.Errorf("vtexplain: unsupported statement type +%v", reflect.TypeOf(stmt))
 		}
 
-		if len(selStmt.From) != 1 {
-			return fmt.Errorf("unsupported select with multiple from clauses")
+		// Gen4 supports more complex queries so we now need to
+		// handle multiple FROM clauses
+		tables := make([]sqlparser.TableIdent, len(selStmt.From))
+		for _, from := range selStmt.From {
+			tables = append(tables, getTables(from)...)
 		}
-
-		tables := getTables(selStmt.From[0])
 		colTypeMap := map[string]querypb.Type{}
 		for _, table := range tables {
 			tableName := sqlparser.String(table)