Show query to honour shard targeting

go/vt/vtgate/executor.go

@@ -1358,9 +1358,9 @@ func (e *Executor) getPlan(vcursor *vcursorImpl, sql string, comments sqlparser.
 	}
 
 	planHash := sha256.New()
-	planHash.Write([]byte(vcursor.planPrefixKey()))
-	planHash.Write([]byte{':'})
-	planHash.Write(hack.StringBytes(query))
+	_, _ = planHash.Write([]byte(vcursor.planPrefixKey()))
+	_, _ = planHash.Write([]byte{':'})
+	_, _ = planHash.Write(hack.StringBytes(query))
 	planKey := hex.EncodeToString(planHash.Sum(nil))
 
 	if plan, ok := e.plans.Get(planKey); ok {

go/vt/vtgate/executor_test.go

@@ -946,6 +946,32 @@ func TestExecutorShow(t *testing.T) {
 	assert.EqualError(t, err, want, query)
 }
 
+func TestExecutorShowTargeted(t *testing.T) {
+	executor, _, sbc2, _ := createLegacyExecutorEnv()
+	session := NewSafeSession(&vtgatepb.Session{TargetString: "TestExecutor/40-60"})
+
+	queries := []string{
+		"show databases",
+		"show variables like 'read_only'",
+		"show collation",
+		"show collation where `Charset` = 'utf8' and `Collation` = 'utf8_bin'",
+		"show tables",
+		fmt.Sprintf("show tables from %v", KsTestUnsharded),
+		"show create table user_seq",
+		"show full columns from table1",
+		"show plugins",
+		"show warnings",
+	}
+
+	for _, sql := range queries {
+		_, err := executor.Execute(ctx, "TestExecutorShowTargeted", session, sql, nil)
+		require.NoError(t, err)
+		assert.NotZero(t, len(sbc2.Queries), "Tablet should have received 'show' query")
+		lastQuery := sbc2.Queries[len(sbc2.Queries)-1].Sql
+		assert.Equal(t, sql, lastQuery, "Got: %v, want %v", lastQuery, sql)
+	}
+}
+
 func TestExecutorUse(t *testing.T) {
 	executor, _, _, _ := createLegacyExecutorEnv()
 	session := NewSafeSession(&vtgatepb.Session{Autocommit: true, TargetString: "@primary"})
@@ -1056,7 +1082,6 @@ func TestExecutorOther(t *testing.T) {
 	}
 
 	stmts := []string{
-		"show tables",
 		"analyze table t1",
 		"describe select * from t1",
 		"explain select * from t1",

go/vt/vtgate/planbuilder/builder.go

@@ -202,7 +202,7 @@ func createInstructionFor(query string, stmt sqlparser.Statement, reservedVars *
 		// Empty by design. Not executed by a plan
 		return nil, nil
 	case *sqlparser.Show:
-		return buildShowPlan(stmt, vschema)
+		return buildRoutePlan(stmt, reservedVars, vschema, buildShowPlan)
 	case *sqlparser.LockTables:
 		return buildRoutePlan(stmt, reservedVars, vschema, buildLockPlan)
 	case *sqlparser.UnlockTables:

go/vt/vtgate/planbuilder/show.go

@@ -41,8 +41,9 @@ const (
 	charset = "charset"
 )
 
-func buildShowPlan(stmt *sqlparser.Show, vschema ContextVSchema) (engine.Primitive, error) {
-	switch show := stmt.Internal.(type) {
+func buildShowPlan(stmt sqlparser.Statement, _ *sqlparser.ReservedVars, vschema ContextVSchema) (engine.Primitive, error) {
+	showStmt := stmt.(*sqlparser.Show)
+	switch show := showStmt.Internal.(type) {
 	case *sqlparser.ShowBasic:
 		return buildShowBasicPlan(show, vschema)
 	case *sqlparser.ShowCreate:

go/vt/vtgate/querylogz.go

@@ -105,9 +105,9 @@ func querylogzHandler(ch chan interface{}, w http.ResponseWriter, r *http.Reques
 			stats, ok := out.(*LogStats)
 			if !ok {
 				err := fmt.Errorf("unexpected value in %s: %#v (expecting value of type %T)", QueryLogger.Name(), out, &LogStats{})
-				io.WriteString(w, `<tr class="error">`)
-				io.WriteString(w, err.Error())
-				io.WriteString(w, "</tr>")
+				_, _ = io.WriteString(w, `<tr class="error">`)
+				_, _ = io.WriteString(w, err.Error())
+				_, _ = io.WriteString(w, "</tr>")
 				log.Error(err)
 				continue
 			}