From a53624120ee5a8c5fae74f37b827c60b2d0c7343 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Andr=C3=A9s=20Taylor?= <andres@planetscale.com>
Date: Wed, 23 Oct 2024 17:17:43 +0200
Subject: [PATCH] bugfix: treat EXPLAIN like SELECT (#17054)

Signed-off-by: Andres Taylor <andres@planetscale.com>
---
 go/vt/vttablet/endtoend/queries_test.go       | 14 +++++++++++
 go/vt/vttablet/endtoend/transaction_test.go   |  2 +-
 .../vttablet/tabletserver/planbuilder/plan.go |  4 +++-
 .../planbuilder/testdata/exec_cases.txt       | 23 +++++++++++--------
 4 files changed, 31 insertions(+), 12 deletions(-)

diff --git a/go/vt/vttablet/endtoend/queries_test.go b/go/vt/vttablet/endtoend/queries_test.go
index 3dad415c1c1..b035013ecc3 100644
--- a/go/vt/vttablet/endtoend/queries_test.go
+++ b/go/vt/vttablet/endtoend/queries_test.go
@@ -121,6 +121,20 @@ var TestQueryCases = []framework.Testable{
 		},
 		RowsReturned: 1,
 	},
+	&framework.TestCase{
+		Name:  "explain with bindvars",
+		Query: "explain select :__vtudvp as `@p` from dual",
+		BindVars: map[string]*querypb.BindVariable{
+			"__vtudvp": sqltypes.Int64BindVariable(1),
+		},
+		Result: [][]string{
+			{"1", "SIMPLE", "", "", "", "", "", "", "", "", "", "No tables used"},
+		},
+		Rewritten: []string{
+			"explain select 1 as `@p` from dual",
+		},
+		RowsReturned: 1,
+	},
 	&framework.TestCase{
 		Name:  "limit",
 		Query: "select /* limit */ eid, id from vitess_a limit :a",
diff --git a/go/vt/vttablet/endtoend/transaction_test.go b/go/vt/vttablet/endtoend/transaction_test.go
index 8f6546df5f1..8c86ecbebe1 100644
--- a/go/vt/vttablet/endtoend/transaction_test.go
+++ b/go/vt/vttablet/endtoend/transaction_test.go
@@ -256,7 +256,7 @@ func TestPrepareRollback(t *testing.T) {
 	err = client.Prepare("aa")
 	if err != nil {
 		client.RollbackPrepared("aa", 0)
-		t.Fatalf(err.Error())
+		t.Fatal(err.Error())
 	}
 	err = client.RollbackPrepared("aa", 0)
 	require.NoError(t, err)
diff --git a/go/vt/vttablet/tabletserver/planbuilder/plan.go b/go/vt/vttablet/tabletserver/planbuilder/plan.go
index 7b1e57c2f90..d37896a84f9 100644
--- a/go/vt/vttablet/tabletserver/planbuilder/plan.go
+++ b/go/vt/vttablet/tabletserver/planbuilder/plan.go
@@ -234,7 +234,9 @@ func Build(env *vtenv.Environment, statement sqlparser.Statement, tables map[str
 	case *sqlparser.Show:
 		plan, err = analyzeShow(stmt, dbName)
 	case *sqlparser.Analyze, sqlparser.Explain:
-		plan, err = &Plan{PlanID: PlanOtherRead}, nil
+		// Analyze and Explain are treated as read-only queries.
+		// We send down a string, and get a table result back.
+		plan = &Plan{PlanID: PlanSelect, FullQuery: GenerateFullQuery(stmt)}
 	case *sqlparser.OtherAdmin:
 		plan, err = &Plan{PlanID: PlanOtherAdmin}, nil
 	case *sqlparser.Savepoint:
diff --git a/go/vt/vttablet/tabletserver/planbuilder/testdata/exec_cases.txt b/go/vt/vttablet/tabletserver/planbuilder/testdata/exec_cases.txt
index 977b3822050..d921180f158 100644
--- a/go/vt/vttablet/tabletserver/planbuilder/testdata/exec_cases.txt
+++ b/go/vt/vttablet/tabletserver/planbuilder/testdata/exec_cases.txt
@@ -763,14 +763,15 @@ options:PassthroughDMLs
 # analyze
 "analyze table a"
 {
-  "PlanID": "OtherRead",
+  "PlanID": "Select",
   "TableName": "",
   "Permissions": [
-      {
-        "TableName": "a",
-        "Role": 1
-      }
-  ]
+    {
+      "TableName": "a",
+      "Role": 1
+    }
+  ],
+  "FullQuery": "analyze table a"
 }
 
 # show
@@ -783,15 +784,17 @@ options:PassthroughDMLs
 # describe
 "describe a"
 {
-  "PlanID": "OtherRead",
-  "TableName": ""
+  "PlanID": "Select",
+  "TableName": "",
+  "FullQuery": "explain a"
 }
 
 # explain
 "explain a"
 {
-  "PlanID": "OtherRead",
-  "TableName": ""
+  "PlanID": "Select",
+  "TableName": "",
+  "FullQuery": "explain a"
 }
 
 # repair