Explain Statement plan improvement (#14928)

Signed-off-by: Harshit Gangal <[email protected]> Signed-off-by: Andres Taylor <[email protected]> Co-authored-by: Andres Taylor <[email protected]>
vitessio · Jan 29, 2024 · 38573f0 · 38573f0
1 parent 2f28985
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diff --git a/changelog/19.0/19.0.0/summary.md b/changelog/19.0/19.0.0/summary.md
@@ -7,6 +7,7 @@
   - **[Deprecations and Deletions](#deprecations-and-deletions)**
     - [VTTablet Flags](#vttablet-flags)
     - [MySQL binary in vitess/lite Docker image](#mysql-binary-in-lite-image)
+    - [Explain Statement Format](#explain-stmt-format)
   - **[Breaking Changes](#breaking-changes)**
      - [ExecuteFetchAsDBA rejects multi-statement SQL](#execute-fetch-as-dba-reject-multi)
   - **[New Stats](#new-stats)**
@@ -18,6 +19,7 @@
     - [Multi Table Delete Support](#multi-table-delete)
     - [`SHOW VSCHEMA KEYSPACES` Query](#show-vschema-keyspaces)
     - [`FOREIGN_KEY_CHECKS` is now a Vitess Aware Variable](#fk-checks-vitess-aware)
+    - [Explain Statement](#explain-statement)
     - [Partial Multi-shard Commit Warnings](#partial-multi-shard-commit-warnings)
   - **[Vttestserver](#vttestserver)**
     - [`--vtcombo-bind-host` flag](#vtcombo-bind-host)
@@ -64,6 +66,11 @@ Below is an example of a kubernetes yaml file before and after upgrading to an o
       mysql80Compatible: mysql:8.0.30 # or even mysql:8.0.34 for instance
 ```
 
+#### <a id="explain-stmt-format"/>Explain Statement Format
+
+Explain statement format `vitess` and `vexplain` were deprecated in v16 and removed in v19 version.
+Use [VExplain Statement](https://vitess.io/docs/19.0/user-guides/sql/vexplain/) for understanding Vitess plans.
+
 ### <a id="breaking-changes"/>Breaking Changes
 
 #### <a id="execute-fetch-as-dba-reject-multi"/>ExecuteFetchAsDBA rejects multi-statement SQL
@@ -131,6 +138,10 @@ mysql> show vschema keyspaces;
 
 When VTGate receives a query to change the `FOREIGN_KEY_CHECKS` value for a session, instead of sending the value down to MySQL, VTGate now keeps track of the value and changes the queries by adding `SET_VAR(FOREIGN_KEY_CHECKS=On/Off)` style query optimizer hints wherever required. 
 
+#### <a id="explain-statement"/>Explain Statement
+
+`Explain` statement can handle routed table queries now. `Explain` is unsupported when the tables involved in the query refers more than one keyspace. Users should use [VExplain Statement](https://vitess.io/docs/19.0/user-guides/sql/vexplain/) in those cases.
+
 #### <a id="partial-multi-shard-commit-warnings"/>Partial Multi-shard Commit Warnings
 
 When using `multi` transaction mode (the default), it is possible for Vitess to successfully commit to one shard, but fail to commit to a subsequent shard, thus breaking the atomicity of a multi-shard transaction.

diff --git a/go/vt/sqlparser/ast_funcs.go b/go/vt/sqlparser/ast_funcs.go
@@ -1815,10 +1815,6 @@ func (ty ExplainType) ToString() string {
 		return TreeStr
 	case JSONType:
 		return JSONStr
-	case VitessType:
-		return VitessStr
-	case VTExplainType:
-		return VTExplainStr
 	case TraditionalType:
 		return TraditionalStr
 	case AnalyzeType:
@@ -2154,8 +2150,8 @@ func (s SelectExprs) AllAggregation() bool {
 	return true
 }
 
-// RemoveKeyspace removes the Qualifier.Qualifier on all ColNames in the AST
-func RemoveKeyspace(in SQLNode) {
+// RemoveKeyspaceInCol removes the Qualifier.Qualifier on all ColNames in the AST
+func RemoveKeyspaceInCol(in SQLNode) {
 	// Walk will only return an error if we return an error from the inner func. safe to ignore here
 	_ = Walk(func(node SQLNode) (kontinue bool, err error) {
 		if col, ok := node.(*ColName); ok && col.Qualifier.Qualifier.NotEmpty() {
@@ -2179,6 +2175,24 @@ func RemoveKeyspaceInTables(in SQLNode) {
 	})
 }
 
+// RemoveKeyspace removes the Qualifier.Qualifier on all ColNames and Qualifier on all TableNames in the AST
+func RemoveKeyspace(in SQLNode) {
+	Rewrite(in, nil, func(cursor *Cursor) bool {
+		switch expr := cursor.Node().(type) {
+		case *ColName:
+			if expr.Qualifier.Qualifier.NotEmpty() {
+				expr.Qualifier.Qualifier = NewIdentifierCS("")
+			}
+		case TableName:
+			if expr.Qualifier.NotEmpty() {
+				expr.Qualifier = NewIdentifierCS("")
+				cursor.Replace(expr)
+			}
+		}
+		return true
+	})
+}
+
 func convertStringToInt(integer string) int {
 	val, _ := strconv.Atoi(integer)
 	return val

diff --git a/go/vt/sqlparser/constants.go b/go/vt/sqlparser/constants.go
@@ -262,10 +262,8 @@ const (
 	EmptyStr       = ""
 	TreeStr        = "tree"
 	JSONStr        = "json"
-	VitessStr      = "vitess"
 	TraditionalStr = "traditional"
 	AnalyzeStr     = "analyze"
-	VTExplainStr   = "vtexplain"
 	QueriesStr     = "queries"
 	AllVExplainStr = "all"
 	PlanStr        = "plan"
@@ -810,8 +808,6 @@ const (
 	EmptyType ExplainType = iota
 	TreeType
 	JSONType
-	VitessType
-	VTExplainType
 	TraditionalType
 	AnalyzeType
 )

diff --git a/go/vt/sqlparser/parse_test.go b/go/vt/sqlparser/parse_test.go
@@ -28,12 +28,11 @@ import (
 	"sync"
 	"testing"
 
-	"vitess.io/vitess/go/test/utils"
-
 	"github.com/google/go-cmp/cmp"
-
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
+
+	"vitess.io/vitess/go/test/utils"
 )
 
 var (
@@ -2524,16 +2523,6 @@ var (
 		input: "explain format = tree select * from t",
 	}, {
 		input: "explain format = json select * from t",
-	}, {
-		input: "explain format = vtexplain select * from t",
-	}, {
-		input: "explain format = vitess select * from t",
-	}, {
-		input:  "describe format = vitess select * from t",
-		output: "explain format = vitess select * from t",
-	}, {
-		input:  "describe format = vtexplain select * from t",
-		output: "explain format = vtexplain select * from t",
 	}, {
 		input: "explain delete from t",
 	}, {