feat: handle info_schema routing for DESCRIBE

Signed-off-by: Andres Taylor <andres@planetscale.com>
vitessio · May 9, 2024 · 85dd84f · 85dd84f
1 parent cbf89bd
commit 85dd84f
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Showing 3 changed files with 63 additions and 33 deletions.
diff --git a/go/vt/vtgate/planbuilder/show.go b/go/vt/vtgate/planbuilder/show.go
@@ -173,31 +173,14 @@ func buildShowTblPlan(show *sqlparser.ShowBasic, vschema plancontext.VSchema) (e
 		show.DbName = sqlparser.NewIdentifierCS("")
 	}
 
-	dest := key.Destination(key.DestinationAnyShard{})
-	var ks *vindexes.Keyspace
-	var err error
-
-	if show.Tbl.Qualifier.NotEmpty() && sqlparser.SystemSchema(show.Tbl.Qualifier.String()) {
-		ks, err = vschema.AnyKeyspace()
-		if err != nil {
-			return nil, err
-		}
-	} else {
-		table, _, _, _, destination, err := vschema.FindTableOrVindex(show.Tbl)
-		if err != nil {
-			return nil, err
-		}
-		if table == nil {
-			return nil, vterrors.VT05004(show.Tbl.Name.String())
-		}
+	ks, dest, table, err := findDestinationToTable(vschema, show.Tbl)
+	if err != nil {
+		return nil, err
+	}
+	if table != nil /*table will be empty for info_schema tables*/ {
 		// Update the table.
 		show.Tbl.Qualifier = sqlparser.NewIdentifierCS("")
 		show.Tbl.Name = table.Name
-
-		if destination != nil {
-			dest = destination
-		}
-		ks = table.Keyspace
 	}
 
 	return &engine.Send{

diff --git a/go/vt/vtgate/planbuilder/testdata/other_read_cases.json b/go/vt/vtgate/planbuilder/testdata/other_read_cases.json
@@ -146,5 +146,26 @@
         "user.music"
       ]
     }
+  },
+  {
+    "comment": "describe info_schema table",
+    "query": "describe information_schema.administrable_role_authorizations",
+    "plan": {
+      "QueryType": "EXPLAIN",
+      "Original": "describe information_schema.administrable_role_authorizations",
+      "Instructions": {
+        "OperatorType": "Send",
+        "Keyspace": {
+          "Name": "main",
+          "Sharded": false
+        },
+        "TargetDestination": "AnyShard()",
+        "Query": "explain information_schema.administrable_role_authorizations",
+        "SingleShardOnly": true
+      },
+      "TablesUsed": [
+        "main.administrable_role_authorizations"
+      ]
+    }
   }
 ]
diff --git a/go/vt/vtgate/planbuilder/vexplain.go b/go/vt/vtgate/planbuilder/vexplain.go
@@ -20,6 +20,8 @@ import (
 	"context"
 	"encoding/json"
 
+	"vitess.io/vitess/go/vt/vtgate/vindexes"
+
 	"vitess.io/vitess/go/sqltypes"
 	"vitess.io/vitess/go/vt/key"
 	querypb "vitess.io/vitess/go/vt/proto/query"
@@ -41,31 +43,55 @@ func buildVExplainPlan(ctx context.Context, vexplainStmt *sqlparser.VExplainStmt
 	return nil, vterrors.Errorf(vtrpcpb.Code_INTERNAL, "[BUG] unexpected vtexplain type: %s", vexplainStmt.Type.ToString())
 }
 
-func explainTabPlan(explain *sqlparser.ExplainTab, vschema plancontext.VSchema) (*planResult, error) {
-	_, _, ks, _, destination, err := vschema.FindTableOrVindex(explain.Table)
-	if err != nil {
-		return nil, err
-	}
-	explain.Table.Qualifier = sqlparser.NewIdentifierCS("")
+func findDestinationToTable(vschema plancontext.VSchema, tbl sqlparser.TableName) (
+	ks *vindexes.Keyspace,
+	destination key.Destination,
+	table *vindexes.Table,
+	err error,
+) {
+	if tbl.Qualifier.NotEmpty() && sqlparser.SystemSchema(tbl.Qualifier.String()) {
+		ks, err = vschema.AnyKeyspace()
+		if err != nil {
+			return
+		}
+	} else {
+		table, _, _, _, destination, err = vschema.FindTableOrVindex(tbl)
+		if err != nil {
+			return
+		}
+		if table == nil {
+			err = vterrors.VT05004(tbl.Name.String())
+			return
+		}
 
+		ks = table.Keyspace
+	}
 	if destination == nil {
 		destination = key.DestinationAnyShard{}
 	}
 
-	keyspace, err := vschema.FindKeyspace(ks)
+	if ks == nil {
+		err = vterrors.VT14004(ks)
+	}
+
+	return
+}
+
+func explainTabPlan(explain *sqlparser.ExplainTab, vschema plancontext.VSchema) (*planResult, error) {
+	ks, destination, table, err := findDestinationToTable(vschema, explain.Table)
 	if err != nil {
 		return nil, err
 	}
-	if keyspace == nil {
-		return nil, vterrors.VT14004(ks)
+	if table != nil /*table will be empty for info_schema tables*/ {
+		explain.Table.Qualifier = sqlparser.NewIdentifierCS("")
 	}
 
 	return newPlanResult(&engine.Send{
-		Keyspace:          keyspace,
+		Keyspace:          ks,
 		TargetDestination: destination,
 		Query:             sqlparser.String(explain),
 		SingleShardOnly:   true,
-	}, singleTable(keyspace.Name, explain.Table.Name.String())), nil
+	}, singleTable(ks.Name, explain.Table.Name.String())), nil
 }
 
 func buildVExplainVtgatePlan(ctx context.Context, explainStatement sqlparser.Statement, reservedVars *sqlparser.ReservedVars, vschema plancontext.VSchema, enableOnlineDDL, enableDirectDDL bool) (*planResult, error) {