Support for 'legacy' (MySQL 5.7.31 at this time) env for fakesqldb; a…

…dd 'Legacy' tests in engine_test

Signed-off-by: Shlomi Noach <2607934+shlomi-noach@users.noreply.github.com>

go/mysql/config/config.go

@@ -2,3 +2,4 @@ package config
 
 const DefaultSQLMode = "ONLY_FULL_GROUP_BY,STRICT_TRANS_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_ENGINE_SUBSTITUTION"
 const DefaultMySQLVersion = "8.0.30"
+const LegacyMySQLVersion = "5.7.31"

go/mysql/fakesqldb/server.go

@@ -166,6 +166,11 @@ type ExpectedExecuteFetch struct {
 
 // New creates a server, and starts listening.
 func New(t testing.TB) *DB {
+	return NewWithEnv(t, vtenv.NewTestEnv())
+}
+
+// NewWithEnv creates a server, and starts listening.
+func NewWithEnv(t testing.TB, env *vtenv.Environment) *DB {
 	// Pick a path for our socket.
 	socketDir, err := os.MkdirTemp("", "fakesqldb")
 	if err != nil {
@@ -185,7 +190,7 @@ func New(t testing.TB) *DB {
 		queryPatternUserCallback: make(map[*regexp.Regexp]func(string)),
 		patternData:              make(map[string]exprResult),
 		lastErrorMu:              sync.Mutex{},
-		env:                      vtenv.NewTestEnv(),
+		env:                      env,
 	}
 
 	db.Handler = db

go/vt/vtenv/vtenv.go

@@ -67,6 +67,12 @@ func NewTestEnv() *Environment {
 	}
 }
 
+func NewLegacyTestEnv() *Environment {
+	env := NewTestEnv()
+	env.mysqlVersion = config.LegacyMySQLVersion
+	return env
+}
+
 func (e *Environment) CollationEnv() *collations.Environment {
 	return e.collationEnv
 }