binary type conversion

pkg/migration/migration_test.go

@@ -2,6 +2,7 @@ package migration
 
 import (
 	"database/sql"
+	"fmt"
 	"os"
 	"testing"
 	"time"
@@ -245,3 +246,48 @@ func TestGeneratedColumns(t *testing.T) {
 	err = migration.Run()
 	assert.NoError(t, err)
 }
+
+type testcase struct {
+	OldType string
+	NewType string
+}
+
+// TestBinaryChecksum tests that we can alter a binary column and still get a checksum match.
+// It works fine from varbinary(50)->varbinary(100), but not from binary(50)->binary(100),
+// without an intermediate cast.
+func TestBinaryChecksum(t *testing.T) {
+	tests := []testcase{
+		{"binary(50)", "varbinary(100)"},
+		{"binary(50)", "binary(100)"},
+		{"varbinary(100)", "varbinary(50)"},
+		{"varbinary(100)", "binary(50)"},
+		{"blob", "tinyblob"},
+		{"tinyblob", "blob"},
+		{"mediumblob", "tinyblob"},
+		{"longblob", "mediumblob"},
+		{"binary(100)", "blob"},
+		{"blob", "binary(100)"},
+	}
+	for _, test := range tests {
+		testutils.RunSQL(t, `DROP TABLE IF EXISTS t1varbin, _t1varbin_new`)
+		table := fmt.Sprintf(`CREATE TABLE t1varbin (
+	 id int not null primary key auto_increment,
+    b %s not null
+	)`, test.OldType)
+		testutils.RunSQL(t, table)
+		testutils.RunSQL(t, `insert into t1varbin values (null, 'abcdefg')`)
+		migration := &Migration{}
+		cfg, err := mysql.ParseDSN(testutils.DSN())
+		assert.NoError(t, err)
+		migration.Host = cfg.Addr
+		migration.Username = cfg.User
+		migration.Password = cfg.Passwd
+		migration.Database = cfg.DBName
+		migration.Threads = 1
+		migration.Checksum = true
+		migration.Table = "t1varbin"
+		migration.Alter = fmt.Sprintf("CHANGE b b %s not null", test.NewType) //nolint: dupword
+		err = migration.Run()
+		assert.NoError(t, err)
+	}
+}

pkg/table/utils.go

@@ -36,8 +36,10 @@ func castableTp(tp string) string {
 		return "datetime"
 	case "varchar", "enum", "set", "text", "mediumtext", "longtext":
 		return "char"
-	case "tinyblob", "blob", "mediumblob", "longblob", "varbinary", "binary":
+	case "tinyblob", "blob", "mediumblob", "longblob", "varbinary":
 		return "binary"
+	case "binary":
+		return "binary(0)" // weirdly only binary needs special handling; blob etc is fine.
 	case "float", "double": // required for MySQL 5.7
 		return "char"
 	case "json":

pkg/table/utils_test.go

@@ -52,7 +52,7 @@ func TestCastableTp(t *testing.T) {
 		{"longblob", "binary"},
 		{"varbinary", "binary"},
 		{"char(100)", "char"},
-		{"binary(100)", "binary"},
+		{"binary(100)", "binary(0)"},
 		{"datetime", "datetime"},
 		{"datetime(6)", "datetime"},
 		{"year", "char"},