Describe table to route based on table name and qualifier

go/test/endtoend/vtgate/misc_test.go

@@ -352,6 +352,9 @@ func TestExplainPassthrough(t *testing.T) {
 	got := fmt.Sprintf("%v", result.Rows)
 	require.Contains(t, got, "SIMPLE") // there is a lot more coming from mysql,
 	// but we are trying to make the test less fragile
+
+	result = exec(t, conn, "explain ks.t1")
+	require.EqualValues(t, 2, len(result.Rows))
 }
 
 func TestXXHash(t *testing.T) {

go/vt/sqlparser/analyzer.go

@@ -84,7 +84,7 @@ func ASTToStatementType(stmt Statement) StatementType {
 		return StmtUse
 	case *OtherRead, *OtherAdmin, *Load:
 		return StmtOther
-	case *Explain:
+	case Explain:
 		return StmtExplain
 	case *Begin:
 		return StmtBegin

go/vt/sqlparser/ast.go

@@ -45,14 +45,13 @@ type (
 
 	// SelectStatement any SELECT statement.
 	SelectStatement interface {
+		Statement
 		iSelectStatement()
-		iStatement()
 		iInsertRows()
 		AddOrder(*Order)
 		SetLimit(*Limit)
 		SetLock(lock Lock)
 		MakeDistinct()
-		SQLNode
 	}
 
 	// DDLStatement represents any DDL Statement
@@ -86,6 +85,12 @@ type (
 		SQLNode
 	}
 
+	// Explain is an interface that represents the Explain statements
+	Explain interface {
+		Statement
+		iExplain()
+	}
+
 	// AddConstraintDefinition represents a ADD CONSTRAINT alter option
 	AddConstraintDefinition struct {
 		ConstraintDefinition *ConstraintDefinition
@@ -505,32 +510,12 @@ type (
 		Name ColIdent
 	}
 
-	// Explain represents an EXPLAIN statement
-	Explain struct {
-		Type      ExplainType
-		Statement Statement
-	}
-
-	// ExplainType is an enum for Explain.Type
-	ExplainType int8
-
 	// CallProc represents a CALL statement
 	CallProc struct {
 		Name   TableName
 		Params Exprs
 	}
 
-	// OtherRead represents a DESCRIBE, or EXPLAIN statement.
-	// It should be used only as an indicator. It does not contain
-	// the full AST for the statement.
-	OtherRead struct{}
-
-	// OtherAdmin represents a misc statement that relies on ADMIN privileges,
-	// such as REPAIR, OPTIMIZE, or TRUNCATE statement.
-	// It should be used only as an indicator. It does not contain
-	// the full AST for the statement.
-	OtherAdmin struct{}
-
 	// LockType is an enum for Lock Types
 	LockType int8
 
@@ -550,6 +535,32 @@ type (
 
 	// UnlockTables represents the unlock statement
 	UnlockTables struct{}
+
+	// ExplainType is an enum for ExplainStmt.Type
+	ExplainType int8
+
+	// ExplainStmt represents an Explain statement
+	ExplainStmt struct {
+		Type      ExplainType
+		Statement Statement
+	}
+
+	// ExplainTab represents the Explain table
+	ExplainTab struct {
+		Table TableName
+		Wild  string
+	}
+
+	// OtherRead represents a DESCRIBE, or EXPLAIN statement.
+	// It should be used only as an indicator. It does not contain
+	// the full AST for the statement.
+	OtherRead struct{}
+
+	// OtherAdmin represents a misc statement that relies on ADMIN privileges,
+	// such as REPAIR, OPTIMIZE, or TRUNCATE statement.
+	// It should be used only as an indicator. It does not contain
+	// the full AST for the statement.
+	OtherAdmin struct{}
 )
 
 func (*Union) iStatement()             {}
@@ -571,7 +582,6 @@ func (*Rollback) iStatement()          {}
 func (*SRollback) iStatement()         {}
 func (*Savepoint) iStatement()         {}
 func (*Release) iStatement()           {}
-func (*Explain) iStatement()           {}
 func (*OtherRead) iStatement()         {}
 func (*OtherAdmin) iStatement()        {}
 func (*Select) iSelectStatement()      {}
@@ -592,6 +602,8 @@ func (*DropView) iStatement()          {}
 func (*TruncateTable) iStatement()     {}
 func (*RenameTable) iStatement()       {}
 func (*CallProc) iStatement()          {}
+func (*ExplainStmt) iStatement()       {}
+func (*ExplainTab) iStatement()        {}
 
 func (*CreateView) iDDLStatement()    {}
 func (*AlterView) iDDLStatement()     {}
@@ -622,6 +634,9 @@ func (*RenameIndex) iAlterOption()             {}
 func (*Validation) iAlterOption()              {}
 func (TableOptions) iAlterOption()             {}
 
+func (*ExplainStmt) iExplain() {}
+func (*ExplainTab) iExplain()  {}
+
 // IsFullyParsed implements the DDLStatement interface
 func (*TruncateTable) IsFullyParsed() bool {
 	return true
@@ -2486,7 +2501,7 @@ func (node *Release) Format(buf *TrackedBuffer) {
 }
 
 // Format formats the node.
-func (node *Explain) Format(buf *TrackedBuffer) {
+func (node *ExplainStmt) Format(buf *TrackedBuffer) {
 	format := ""
 	switch node.Type {
 	case EmptyType: // do nothing
@@ -2498,6 +2513,14 @@ func (node *Explain) Format(buf *TrackedBuffer) {
 	buf.astPrintf(node, "explain %s%v", format, node.Statement)
 }
 
+// Format formats the node.
+func (node *ExplainTab) Format(buf *TrackedBuffer) {
+	buf.astPrintf(node, "explain %v", node.Table)
+	if node.Wild != "" {
+		buf.astPrintf(node, " %s", node.Wild)
+	}
+}
+
 // Format formats the node.
 func (node *CallProc) Format(buf *TrackedBuffer) {
 	buf.astPrintf(node, "call %v(%v)", node.Name, node.Params)

go/vt/sqlparser/parse_test.go

@@ -1534,13 +1534,13 @@ var (
 		output: "explain select * from t",
 	}, {
 		input:  "desc foobar",
-		output: "otherread",
+		output: "explain foobar",
 	}, {
-		input:  "explain t1",
-		output: "otherread",
+		input: "explain t1",
 	}, {
-		input:  "explain t1 col",
-		output: "otherread",
+		input: "explain t1 col",
+	}, {
+		input: "explain t1 '%col%'",
 	}, {
 		input: "explain select * from t",
 	}, {

go/vt/sqlparser/sql.y

@@ -2728,21 +2728,21 @@ wild_opt:
   }
 | sql_id
   {
-    $$ = "" 
+    $$ = $1.val
   }
 | STRING
   {
-    $$ = "" 
+    $$ = "'" + string($1) + "'"
   }
-  
+
 explain_statement:
   explain_synonyms table_name wild_opt
   {
-    $$ = &OtherRead{}
+    $$ = &ExplainTab{Table: $2, Wild: $3}
   }
 | explain_synonyms explain_format_opt explainable_statement
   {
-    $$ = &Explain{Type: $2, Statement: $3}
+    $$ = &ExplainStmt{Type: $2, Statement: $3}
   }
 
 other_statement:

go/vt/vtgate/executor_test.go

@@ -1035,27 +1035,26 @@ func TestExecutorOther(t *testing.T) {
 
 	for _, stmt := range stmts {
 		for _, tc := range tcs {
-			sbc1.ExecCount.Set(0)
-			sbc2.ExecCount.Set(0)
-			sbclookup.ExecCount.Set(0)
-
-			_, err := executor.Execute(ctx, "TestExecute", NewSafeSession(&vtgatepb.Session{TargetString: tc.targetStr}), stmt, nil)
-			if tc.hasNoKeyspaceErr {
-				assert.Error(t, err, errNoKeyspace)
-			} else if tc.hasDestinationShardErr {
-				assert.Errorf(t, err, "Destination can only be a single shard for statement: %s, got: DestinationExactKeyRange(-)", stmt)
-			} else {
-				assert.NoError(t, err)
-			}
-
-			diff := cmp.Diff(tc.wantCnts, cnts{
-				Sbc1Cnt:      sbc1.ExecCount.Get(),
-				Sbc2Cnt:      sbc2.ExecCount.Get(),
-				SbcLookupCnt: sbclookup.ExecCount.Get(),
+			t.Run(fmt.Sprintf("%s-%s", stmt, tc.targetStr), func(t *testing.T) {
+				sbc1.ExecCount.Set(0)
+				sbc2.ExecCount.Set(0)
+				sbclookup.ExecCount.Set(0)
+
+				_, err := executor.Execute(ctx, "TestExecute", NewSafeSession(&vtgatepb.Session{TargetString: tc.targetStr}), stmt, nil)
+				if tc.hasNoKeyspaceErr {
+					assert.Error(t, err, errNoKeyspace)
+				} else if tc.hasDestinationShardErr {
+					assert.Errorf(t, err, "Destination can only be a single shard for statement: %s", stmt)
+				} else {
+					assert.NoError(t, err)
+				}
+
+				utils.MustMatch(t, tc.wantCnts, cnts{
+					Sbc1Cnt:      sbc1.ExecCount.Get(),
+					Sbc2Cnt:      sbc2.ExecCount.Get(),
+					SbcLookupCnt: sbclookup.ExecCount.Get(),
+				})
 			})
-			if diff != "" {
-				t.Errorf("stmt: %s\ntc: %+v\n-want,+got:\n%s", stmt, tc, diff)
-			}
 		}
 	}
 }

go/vt/vtgate/planbuilder/builder.go

@@ -158,15 +158,8 @@ func createInstructionFor(query string, stmt sqlparser.Statement, vschema Contex
 		return buildVSchemaDDLPlan(stmt, vschema)
 	case *sqlparser.Use:
 		return buildUsePlan(stmt, vschema)
-	case *sqlparser.Explain:
-		if stmt.Type == sqlparser.VitessType {
-			innerInstruction, err := createInstructionFor(query, stmt.Statement, vschema)
-			if err != nil {
-				return nil, err
-			}
-			return buildExplainPlan(innerInstruction)
-		}
-		return buildOtherReadAndAdmin(query, vschema)
+	case sqlparser.Explain:
+		return buildExplainPlan(stmt, vschema)
 	case *sqlparser.OtherRead, *sqlparser.OtherAdmin:
 		return buildOtherReadAndAdmin(query, vschema)
 	case *sqlparser.Set: