From a2a33844a45e17ba2c1ecda288533be60373a1ba Mon Sep 17 00:00:00 2001
From: Harshit Gangal <harshit@planetscale.com>
Date: Wed, 3 Feb 2021 18:04:39 +0530
Subject: [PATCH 1/8] added desc parsing test

Signed-off-by: Harshit Gangal <harshit@planetscale.com>
---
 go/vt/sqlparser/parse_test.go | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/go/vt/sqlparser/parse_test.go b/go/vt/sqlparser/parse_test.go
index ea1ece1d5bf..51a7bd7ed10 100644
--- a/go/vt/sqlparser/parse_test.go
+++ b/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",
 	}, {

From cefc1042a35a80b99956601871d06594c2d928b7 Mon Sep 17 00:00:00 2001
From: Harshit Gangal <harshit@planetscale.com>
Date: Thu, 4 Feb 2021 00:18:24 +0530
Subject: [PATCH 2/8] add full parsing for describe

Signed-off-by: Harshit Gangal <harshit@planetscale.com>
---
 go/vt/sqlparser/ast.go      | 61 +++++++++++++++++++++++++------------
 go/vt/sqlparser/rewriter.go |  7 +++++
 go/vt/sqlparser/sql.go      |  6 ++--
 go/vt/sqlparser/sql.y       |  8 ++---
 4 files changed, 55 insertions(+), 27 deletions(-)

diff --git a/go/vt/sqlparser/ast.go b/go/vt/sqlparser/ast.go
index 284f90578b2..7475dfac189 100644
--- a/go/vt/sqlparser/ast.go
+++ b/go/vt/sqlparser/ast.go
@@ -86,6 +86,12 @@ type (
 		SQLNode
 	}
 
+	// Explain is an interface that represents the Explain statements
+	Explain interface {
+		iExplain()
+		Statement
+	}
+
 	// AddConstraintDefinition represents a ADD CONSTRAINT alter option
 	AddConstraintDefinition struct {
 		ConstraintDefinition *ConstraintDefinition
@@ -505,32 +511,12 @@ 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 +536,32 @@ type (
 
 	// UnlockTables represents the unlock statement
 	UnlockTables struct{}
+
+	// ExplainType is an enum for Explain.Type
+	ExplainType int8
+
+	// Explain represents an EXPLAIN statement
+	ExplainStmt struct {
+		Type      ExplainType
+		Statement Statement
+	}
+
+	// ExplainTab represents the explain table statement
+	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()             {}
@@ -592,6 +604,7 @@ func (*DropView) iStatement()          {}
 func (*TruncateTable) iStatement()     {}
 func (*RenameTable) iStatement()       {}
 func (*CallProc) iStatement()          {}
+func (*Desc) iStatement()              {}
 
 func (*CreateView) iDDLStatement()    {}
 func (*AlterView) iDDLStatement()     {}
@@ -2498,6 +2511,14 @@ func (node *Explain) Format(buf *TrackedBuffer) {
 	buf.astPrintf(node, "explain %s%v", format, node.Statement)
 }
 
+// Format formats the node.
+func (node *Desc) 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)
diff --git a/go/vt/sqlparser/rewriter.go b/go/vt/sqlparser/rewriter.go
index 19f1050b06f..c592c630557 100644
--- a/go/vt/sqlparser/rewriter.go
+++ b/go/vt/sqlparser/rewriter.go
@@ -342,6 +342,10 @@ func replaceDerivedTableSelect(newNode, parent SQLNode) {
 	parent.(*DerivedTable).Select = newNode.(SelectStatement)
 }
 
+func replaceDescTable(newNode, parent SQLNode) {
+	parent.(*Desc).Table = newNode.(TableName)
+}
+
 func replaceDropColumnName(newNode, parent SQLNode) {
 	parent.(*DropColumn).Name = newNode.(*ColName)
 }
@@ -1263,6 +1267,9 @@ func (a *application) apply(parent, node SQLNode, replacer replacerFunc) {
 	case *DerivedTable:
 		a.apply(node, n.Select, replaceDerivedTableSelect)
 
+	case *Desc:
+		a.apply(node, n.Table, replaceDescTable)
+
 	case *DropColumn:
 		a.apply(node, n.Name, replaceDropColumnName)
 
diff --git a/go/vt/sqlparser/sql.go b/go/vt/sqlparser/sql.go
index eea7d1bc634..e85eac8f6b1 100644
--- a/go/vt/sqlparser/sql.go
+++ b/go/vt/sqlparser/sql.go
@@ -8291,19 +8291,19 @@ yydefault:
 		yyDollar = yyS[yypt-1 : yypt+1]
 //line sql.y:2730
 		{
-			yyVAL.str = ""
+			yyVAL.str = yyDollar[1].colIdent.val
 		}
 	case 513:
 		yyDollar = yyS[yypt-1 : yypt+1]
 //line sql.y:2734
 		{
-			yyVAL.str = ""
+			yyVAL.str = "'" + string(yyDollar[1].bytes) + "'"
 		}
 	case 514:
 		yyDollar = yyS[yypt-3 : yypt+1]
 //line sql.y:2740
 		{
-			yyVAL.statement = &OtherRead{}
+			yyVAL.statement = &Desc{Table: yyDollar[2].tableName, Wild: yyDollar[3].str}
 		}
 	case 515:
 		yyDollar = yyS[yypt-3 : yypt+1]
diff --git a/go/vt/sqlparser/sql.y b/go/vt/sqlparser/sql.y
index 048a14c17de..0ae0e7072d1 100644
--- a/go/vt/sqlparser/sql.y
+++ b/go/vt/sqlparser/sql.y
@@ -2728,17 +2728,17 @@ wild_opt:
   }
 | sql_id
   {
-    $$ = "" 
+    $$ = $1.val
   }
 | STRING
   {
-    $$ = "" 
+    $$ = "'" + string($1) + "'"
   }
-  
+
 explain_statement:
   explain_synonyms table_name wild_opt
   {
-    $$ = &OtherRead{}
+    $$ = &Desc{Table: $2, Wild: $3}
   }
 | explain_synonyms explain_format_opt explainable_statement
   {

From d11253e0c675e01157c762f40700cb11d3676d89 Mon Sep 17 00:00:00 2001
From: Harshit Gangal <harshit@planetscale.com>
Date: Thu, 4 Feb 2021 22:24:49 +0530
Subject: [PATCH 3/8] added explain interface and explain statement & explain
 table as type of it

Signed-off-by: Harshit Gangal <harshit@planetscale.com>
---
 go/vt/sqlparser/analyzer.go |  2 +-
 go/vt/sqlparser/ast.go      | 20 +++++++++++---------
 go/vt/sqlparser/rewriter.go | 22 +++++++++++-----------
 go/vt/sqlparser/sql.go      |  4 ++--
 go/vt/sqlparser/sql.y       |  4 ++--
 5 files changed, 27 insertions(+), 25 deletions(-)

diff --git a/go/vt/sqlparser/analyzer.go b/go/vt/sqlparser/analyzer.go
index 4d7c9424f6a..b44f5b36b1c 100644
--- a/go/vt/sqlparser/analyzer.go
+++ b/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
diff --git a/go/vt/sqlparser/ast.go b/go/vt/sqlparser/ast.go
index 7475dfac189..aec1b9c8507 100644
--- a/go/vt/sqlparser/ast.go
+++ b/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
@@ -537,16 +536,16 @@ type (
 	// UnlockTables represents the unlock statement
 	UnlockTables struct{}
 
-	// ExplainType is an enum for Explain.Type
+	// ExplainType is an enum for ExplainStmt.Type
 	ExplainType int8
 
-	// Explain represents an EXPLAIN statement
+	// ExplainStmt represents an Explain statement
 	ExplainStmt struct {
 		Type      ExplainType
 		Statement Statement
 	}
 
-	// ExplainTab represents the explain table statement
+	// ExplainTab represents the Explain table
 	ExplainTab struct {
 		Table TableName
 		Wild  string
@@ -583,7 +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()      {}
@@ -604,7 +602,8 @@ func (*DropView) iStatement()          {}
 func (*TruncateTable) iStatement()     {}
 func (*RenameTable) iStatement()       {}
 func (*CallProc) iStatement()          {}
-func (*Desc) iStatement()              {}
+func (*ExplainStmt) iStatement()       {}
+func (*ExplainTab) iStatement()        {}
 
 func (*CreateView) iDDLStatement()    {}
 func (*AlterView) iDDLStatement()     {}
@@ -635,6 +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
@@ -2499,7 +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
@@ -2512,7 +2514,7 @@ func (node *Explain) Format(buf *TrackedBuffer) {
 }
 
 // Format formats the node.
-func (node *Desc) Format(buf *TrackedBuffer) {
+func (node *ExplainTab) Format(buf *TrackedBuffer) {
 	buf.astPrintf(node, "explain %v", node.Table)
 	if node.Wild != "" {
 		buf.astPrintf(node, " %s", node.Wild)
diff --git a/go/vt/sqlparser/rewriter.go b/go/vt/sqlparser/rewriter.go
index c592c630557..d4073481c10 100644
--- a/go/vt/sqlparser/rewriter.go
+++ b/go/vt/sqlparser/rewriter.go
@@ -342,10 +342,6 @@ func replaceDerivedTableSelect(newNode, parent SQLNode) {
 	parent.(*DerivedTable).Select = newNode.(SelectStatement)
 }
 
-func replaceDescTable(newNode, parent SQLNode) {
-	parent.(*Desc).Table = newNode.(TableName)
-}
-
 func replaceDropColumnName(newNode, parent SQLNode) {
 	parent.(*DropColumn).Name = newNode.(*ColName)
 }
@@ -362,8 +358,12 @@ func replaceExistsExprSubquery(newNode, parent SQLNode) {
 	parent.(*ExistsExpr).Subquery = newNode.(*Subquery)
 }
 
-func replaceExplainStatement(newNode, parent SQLNode) {
-	parent.(*Explain).Statement = newNode.(Statement)
+func replaceExplainStmtStatement(newNode, parent SQLNode) {
+	parent.(*ExplainStmt).Statement = newNode.(Statement)
+}
+
+func replaceExplainTabTable(newNode, parent SQLNode) {
+	parent.(*ExplainTab).Table = newNode.(TableName)
 }
 
 type replaceExprsItems int
@@ -1267,9 +1267,6 @@ func (a *application) apply(parent, node SQLNode, replacer replacerFunc) {
 	case *DerivedTable:
 		a.apply(node, n.Select, replaceDerivedTableSelect)
 
-	case *Desc:
-		a.apply(node, n.Table, replaceDescTable)
-
 	case *DropColumn:
 		a.apply(node, n.Name, replaceDropColumnName)
 
@@ -1286,8 +1283,11 @@ func (a *application) apply(parent, node SQLNode, replacer replacerFunc) {
 	case *ExistsExpr:
 		a.apply(node, n.Subquery, replaceExistsExprSubquery)
 
-	case *Explain:
-		a.apply(node, n.Statement, replaceExplainStatement)
+	case *ExplainStmt:
+		a.apply(node, n.Statement, replaceExplainStmtStatement)
+
+	case *ExplainTab:
+		a.apply(node, n.Table, replaceExplainTabTable)
 
 	case Exprs:
 		replacer := replaceExprsItems(0)
diff --git a/go/vt/sqlparser/sql.go b/go/vt/sqlparser/sql.go
index e85eac8f6b1..82322dd688f 100644
--- a/go/vt/sqlparser/sql.go
+++ b/go/vt/sqlparser/sql.go
@@ -8303,13 +8303,13 @@ yydefault:
 		yyDollar = yyS[yypt-3 : yypt+1]
 //line sql.y:2740
 		{
-			yyVAL.statement = &Desc{Table: yyDollar[2].tableName, Wild: yyDollar[3].str}
+			yyVAL.statement = &ExplainTab{Table: yyDollar[2].tableName, Wild: yyDollar[3].str}
 		}
 	case 515:
 		yyDollar = yyS[yypt-3 : yypt+1]
 //line sql.y:2744
 		{
-			yyVAL.statement = &Explain{Type: yyDollar[2].explainType, Statement: yyDollar[3].statement}
+			yyVAL.statement = &ExplainStmt{Type: yyDollar[2].explainType, Statement: yyDollar[3].statement}
 		}
 	case 516:
 		yyDollar = yyS[yypt-2 : yypt+1]
diff --git a/go/vt/sqlparser/sql.y b/go/vt/sqlparser/sql.y
index 0ae0e7072d1..91945f86166 100644
--- a/go/vt/sqlparser/sql.y
+++ b/go/vt/sqlparser/sql.y
@@ -2738,11 +2738,11 @@ wild_opt:
 explain_statement:
   explain_synonyms table_name wild_opt
   {
-    $$ = &Desc{Table: $2, Wild: $3}
+    $$ = &ExplainTab{Table: $2, Wild: $3}
   }
 | explain_synonyms explain_format_opt explainable_statement
   {
-    $$ = &Explain{Type: $2, Statement: $3}
+    $$ = &ExplainStmt{Type: $2, Statement: $3}
   }
 
 other_statement:

From 63329ceb81165f9e1ee24aa86c029bd664462128 Mon Sep 17 00:00:00 2001
From: Harshit Gangal <harshit@planetscale.com>
Date: Thu, 4 Feb 2021 22:25:46 +0530
Subject: [PATCH 4/8] plan explain table correctly

Signed-off-by: Harshit Gangal <harshit@planetscale.com>
---
 go/vt/vtgate/executor_test.go                 | 39 ++++++------
 go/vt/vtgate/planbuilder/builder.go           | 11 +---
 go/vt/vtgate/planbuilder/explain.go           | 62 +++++++++++++++----
 go/vt/vtgate/planbuilder/other_read.go        |  1 -
 .../planbuilder/testdata/other_read_cases.txt |  4 +-
 5 files changed, 74 insertions(+), 43 deletions(-)

diff --git a/go/vt/vtgate/executor_test.go b/go/vt/vtgate/executor_test.go
index a92b107b291..628e51618e8 100644
--- a/go/vt/vtgate/executor_test.go
+++ b/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)
-			}
 		}
 	}
 }
diff --git a/go/vt/vtgate/planbuilder/builder.go b/go/vt/vtgate/planbuilder/builder.go
index 27122528233..2f1463af163 100644
--- a/go/vt/vtgate/planbuilder/builder.go
+++ b/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:
diff --git a/go/vt/vtgate/planbuilder/explain.go b/go/vt/vtgate/planbuilder/explain.go
index 74d912dddbf..e13b423bf19 100644
--- a/go/vt/vtgate/planbuilder/explain.go
+++ b/go/vt/vtgate/planbuilder/explain.go
@@ -20,26 +20,53 @@ import (
 	"strings"
 
 	"vitess.io/vitess/go/sqltypes"
+	"vitess.io/vitess/go/vt/key"
 	querypb "vitess.io/vitess/go/vt/proto/query"
+	vtrpcpb "vitess.io/vitess/go/vt/proto/vtrpc"
+	"vitess.io/vitess/go/vt/sqlparser"
+	"vitess.io/vitess/go/vt/vterrors"
 	"vitess.io/vitess/go/vt/vtgate/engine"
 )
 
-func extractQuery(m map[string]interface{}) string {
-	queryObj, ok := m["Query"]
-	if !ok {
-		return ""
+// Builds an explain-plan for the given Primitive
+func buildExplainPlan(stmt sqlparser.Explain, vschema ContextVSchema) (engine.Primitive, error) {
+	switch explain := stmt.(type) {
+	case *sqlparser.ExplainTab:
+		return explainTabPlan(explain, vschema)
+	case *sqlparser.ExplainStmt:
+		if explain.Type == sqlparser.VitessType {
+			return buildVitessTypePlan(explain, vschema)
+		}
+		return buildOtherReadAndAdmin(sqlparser.String(explain), vschema)
 	}
-	query, ok := queryObj.(string)
-	if !ok {
-		return ""
+	return nil, vterrors.Errorf(vtrpcpb.Code_INTERNAL, "BUG unexpected explain type: %T", stmt)
+}
+
+func explainTabPlan(explain *sqlparser.ExplainTab, vschema ContextVSchema) (engine.Primitive, error) {
+	table, _, _, _, destination, err := vschema.FindTableOrVindex(explain.Table)
+	if err != nil {
+		return nil, err
 	}
+	explain.Table.Qualifier = sqlparser.NewTableIdent("")
 
-	return query
+	if destination == nil {
+		destination = key.DestinationAnyShard{}
+	}
+
+	return &engine.Send{
+		Keyspace:          table.Keyspace,
+		TargetDestination: destination,
+		Query:             sqlparser.String(explain),
+		SingleShardOnly:   true,
+	}, nil
 }
 
-// Builds an explain-plan for the given Primitive
-func buildExplainPlan(input engine.Primitive) (engine.Primitive, error) {
-	descriptions := treeLines(engine.PrimitiveToPlanDescription(input))
+func buildVitessTypePlan(explain *sqlparser.ExplainStmt, vschema ContextVSchema) (engine.Primitive, error) {
+	innerInstruction, err := createInstructionFor(sqlparser.String(explain.Statement), explain.Statement, vschema)
+	if err != nil {
+		return nil, err
+	}
+	descriptions := treeLines(engine.PrimitiveToPlanDescription(innerInstruction))
 
 	var rows [][]sqltypes.Value
 	for _, line := range descriptions {
@@ -74,6 +101,19 @@ func buildExplainPlan(input engine.Primitive) (engine.Primitive, error) {
 	return engine.NewRowsPrimitive(rows, fields), nil
 }
 
+func extractQuery(m map[string]interface{}) string {
+	queryObj, ok := m["Query"]
+	if !ok {
+		return ""
+	}
+	query, ok := queryObj.(string)
+	if !ok {
+		return ""
+	}
+
+	return query
+}
+
 type description struct {
 	header string
 	descr  engine.PrimitiveDescription
diff --git a/go/vt/vtgate/planbuilder/other_read.go b/go/vt/vtgate/planbuilder/other_read.go
index ac9654a9498..aaedecc634f 100644
--- a/go/vt/vtgate/planbuilder/other_read.go
+++ b/go/vt/vtgate/planbuilder/other_read.go
@@ -35,7 +35,6 @@ func buildOtherReadAndAdmin(sql string, vschema ContextVSchema) (engine.Primitiv
 		Keyspace:          keyspace,
 		TargetDestination: destination,
 		Query:             sql, //This is original sql query to be passed as the parser can provide partial ddl AST.
-		IsDML:             false,
 		SingleShardOnly:   true,
 	}, nil
 }
diff --git a/go/vt/vtgate/planbuilder/testdata/other_read_cases.txt b/go/vt/vtgate/planbuilder/testdata/other_read_cases.txt
index d183afb081c..0d52d47f4e8 100644
--- a/go/vt/vtgate/planbuilder/testdata/other_read_cases.txt
+++ b/go/vt/vtgate/planbuilder/testdata/other_read_cases.txt
@@ -57,7 +57,7 @@
     },
     "TargetDestination": "AnyShard()",
     "IsDML": false,
-    "Query": "describe select * from t",
+    "Query": "explain select * from t",
     "SingleShardOnly": true
   }
 }
@@ -75,7 +75,7 @@
     },
     "TargetDestination": "AnyShard()",
     "IsDML": false,
-    "Query": "desc select * from t",
+    "Query": "explain select * from t",
     "SingleShardOnly": true
   }
 }

From 34bff41590a429292f599dd55d6675e6a46df1cf Mon Sep 17 00:00:00 2001
From: Harshit Gangal <harshit@planetscale.com>
Date: Thu, 4 Feb 2021 23:35:43 +0530
Subject: [PATCH 5/8] fix explain plan in tabletserver

Signed-off-by: Harshit Gangal <harshit@planetscale.com>
---
 go/vt/vttablet/tabletserver/planbuilder/permission.go         | 2 +-
 go/vt/vttablet/tabletserver/planbuilder/plan.go               | 4 ++--
 .../tabletserver/planbuilder/testdata/stream_cases.txt        | 2 +-
 3 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/go/vt/vttablet/tabletserver/planbuilder/permission.go b/go/vt/vttablet/tabletserver/planbuilder/permission.go
index 1bad105b4e7..80949b76c02 100644
--- a/go/vt/vttablet/tabletserver/planbuilder/permission.go
+++ b/go/vt/vttablet/tabletserver/planbuilder/permission.go
@@ -57,7 +57,7 @@ func BuildPermissions(stmt sqlparser.Statement) []Permission {
 		}
 	case *sqlparser.OtherAdmin, *sqlparser.CallProc, *sqlparser.Begin, *sqlparser.Commit, *sqlparser.Rollback,
 		*sqlparser.Load, *sqlparser.Savepoint, *sqlparser.Release, *sqlparser.SRollback, *sqlparser.Set, *sqlparser.Show,
-		*sqlparser.OtherRead, *sqlparser.Explain:
+		*sqlparser.OtherRead, sqlparser.Explain:
 		// no op
 	default:
 		panic(fmt.Errorf("BUG: unexpected statement type: %T", node))
diff --git a/go/vt/vttablet/tabletserver/planbuilder/plan.go b/go/vt/vttablet/tabletserver/planbuilder/plan.go
index 71d9758354b..340e7edb014 100644
--- a/go/vt/vttablet/tabletserver/planbuilder/plan.go
+++ b/go/vt/vttablet/tabletserver/planbuilder/plan.go
@@ -202,7 +202,7 @@ func Build(statement sqlparser.Statement, tables map[string]*schema.Table, isRes
 		plan = &Plan{PlanID: PlanDDL, FullQuery: fullQuery}
 	case *sqlparser.Show:
 		plan, err = analyzeShow(stmt, dbName)
-	case *sqlparser.OtherRead, *sqlparser.Explain:
+	case *sqlparser.OtherRead, sqlparser.Explain:
 		plan, err = &Plan{PlanID: PlanOtherRead}, nil
 	case *sqlparser.OtherAdmin:
 		plan, err = &Plan{PlanID: PlanOtherAdmin}, nil
@@ -254,7 +254,7 @@ func BuildStreaming(sql string, tables map[string]*schema.Table, isReservedConn
 			return nil, vterrors.New(vtrpcpb.Code_FAILED_PRECONDITION, "select with lock not allowed for streaming")
 		}
 		plan.Table = lookupTable(stmt.From, tables)
-	case *sqlparser.OtherRead, *sqlparser.Show, *sqlparser.Union, *sqlparser.CallProc:
+	case *sqlparser.OtherRead, *sqlparser.Show, *sqlparser.Union, *sqlparser.CallProc, sqlparser.Explain:
 		// pass
 	default:
 		return nil, vterrors.Errorf(vtrpcpb.Code_FAILED_PRECONDITION, "'%v' not allowed for streaming", sqlparser.String(stmt))
diff --git a/go/vt/vttablet/tabletserver/planbuilder/testdata/stream_cases.txt b/go/vt/vttablet/tabletserver/planbuilder/testdata/stream_cases.txt
index 4724e019b94..16ca07e1907 100644
--- a/go/vt/vttablet/tabletserver/planbuilder/testdata/stream_cases.txt
+++ b/go/vt/vttablet/tabletserver/planbuilder/testdata/stream_cases.txt
@@ -50,7 +50,7 @@
 {
   "PlanID": "SelectStream",
   "TableName": "",
-  "FullQuery": "otherread"
+  "FullQuery": "explain foo"
 }
 
 # dml

From 4672a0b4c0c0674e9e628e3f3cfa674b0bac8a0e Mon Sep 17 00:00:00 2001
From: Harshit Gangal <harshit@planetscale.com>
Date: Thu, 4 Feb 2021 23:58:03 +0530
Subject: [PATCH 6/8] added e2e test

Signed-off-by: Harshit Gangal <harshit@planetscale.com>
---
 go/test/endtoend/vtgate/misc_test.go      | 3 +++
 go/vt/vttablet/sandboxconn/sandboxconn.go | 2 +-
 2 files changed, 4 insertions(+), 1 deletion(-)

diff --git a/go/test/endtoend/vtgate/misc_test.go b/go/test/endtoend/vtgate/misc_test.go
index 253b0363490..133e8397d98 100644
--- a/go/test/endtoend/vtgate/misc_test.go
+++ b/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) {
diff --git a/go/vt/vttablet/sandboxconn/sandboxconn.go b/go/vt/vttablet/sandboxconn/sandboxconn.go
index 4589a749084..b2187b4742c 100644
--- a/go/vt/vttablet/sandboxconn/sandboxconn.go
+++ b/go/vt/vttablet/sandboxconn/sandboxconn.go
@@ -511,7 +511,7 @@ func (sbc *SandboxConn) getNextResult(stmt sqlparser.Statement) *sqltypes.Result
 	case *sqlparser.Select,
 		*sqlparser.Union,
 		*sqlparser.Show,
-		*sqlparser.Explain,
+		sqlparser.Explain,
 		*sqlparser.OtherRead:
 		return SingleRowResult
 	case *sqlparser.Set,

From 15495afc3f0a4fc89af01267f29f477351e83b7d Mon Sep 17 00:00:00 2001
From: Harshit Gangal <harshit@planetscale.com>
Date: Fri, 5 Feb 2021 00:25:40 +0530
Subject: [PATCH 7/8] fix wrangler test

Signed-off-by: Harshit Gangal <harshit@planetscale.com>
---
 go/vt/wrangler/vexec_test.go | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/go/vt/wrangler/vexec_test.go b/go/vt/wrangler/vexec_test.go
index 1ed3ccdc1d1..43dbde69db4 100644
--- a/go/vt/wrangler/vexec_test.go
+++ b/go/vt/wrangler/vexec_test.go
@@ -378,7 +378,7 @@ func TestVExecValidations(t *testing.T) {
 		{
 			name:        "unsupported query",
 			query:       "describe _vt.vreplication",
-			errorString: "query not supported by vexec: otherread",
+			errorString: "query not supported by vexec: explain _vt.vreplication",
 		},
 	}
 	for _, bq := range badQueries {

From f8dcedfeaa454c6f476e403d60ca6bd0370cf678 Mon Sep 17 00:00:00 2001
From: Harshit Gangal <harshit@planetscale.com>
Date: Sun, 7 Feb 2021 23:00:47 +0530
Subject: [PATCH 8/8] addressed review comments

Signed-off-by: Harshit Gangal <harshit@planetscale.com>
---
 go/vt/sqlparser/ast.go | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/go/vt/sqlparser/ast.go b/go/vt/sqlparser/ast.go
index aec1b9c8507..d2d7adfd951 100644
--- a/go/vt/sqlparser/ast.go
+++ b/go/vt/sqlparser/ast.go
@@ -87,8 +87,8 @@ type (
 
 	// Explain is an interface that represents the Explain statements
 	Explain interface {
-		iExplain()
 		Statement
+		iExplain()
 	}
 
 	// AddConstraintDefinition represents a ADD CONSTRAINT alter option