schemadiff: TableCharsetCollateStrategy hint

go/vt/schemadiff/table.go

@@ -863,6 +863,12 @@ func (c *CreateTableEntity) diffOptions(alterTable *sqlparser.AlterTable,
 				// skip
 			case "AVG_ROW_LENGTH":
 				// skip. MyISAM only, not interesting
+			case "CHARSET":
+				switch hints.TableCharsetCollateStrategy {
+				case TableCharsetCollateStrict:
+					tableOption = &sqlparser.TableOption{String: ""}
+					// in all other strategies we ignore the charset
+				}
 			case "CHECKSUM":
 				tableOption = &sqlparser.TableOption{Value: sqlparser.NewIntLiteral("0")}
 			case "COLLATE":
@@ -930,6 +936,18 @@ func (c *CreateTableEntity) diffOptions(alterTable *sqlparser.AlterTable,
 				// options are different.
 				// However, we don't automatically apply these changes. It depends on the option!
 				switch strings.ToUpper(t1Option.Name) {
+				case "CHARSET", "COLLATE":
+					switch hints.TableCharsetCollateStrategy {
+					case TableCharsetCollateStrict:
+						alterTableOptions = append(alterTableOptions, t2Option)
+					case TableCharsetCollateIgnoreEmpty:
+						if t1Option.String != "" && t2Option.String != "" {
+							alterTableOptions = append(alterTableOptions, t2Option)
+						}
+						// if one is empty, we ignore
+					case TableCharsetCollateIgnoreAlways:
+						// ignore always
+					}
 				case "AUTO_INCREMENT":
 					switch hints.AutoIncrementStrategy {
 					case AutoIncrementApplyAlways:
@@ -961,6 +979,12 @@ func (c *CreateTableEntity) diffOptions(alterTable *sqlparser.AlterTable,
 	for _, t2Option := range t2Options {
 		if _, ok := t1OptionsMap[t2Option.Name]; !ok {
 			switch strings.ToUpper(t2Option.Name) {
+			case "CHARSET", "COLLATE":
+				switch hints.TableCharsetCollateStrategy {
+				case TableCharsetCollateStrict:
+					alterTableOptions = append(alterTableOptions, t2Option)
+					// in all other strategies we ignore the charset
+				}
 			case "AUTO_INCREMENT":
 				switch hints.AutoIncrementStrategy {
 				case AutoIncrementApplyAlways, AutoIncrementApplyHigher:

go/vt/schemadiff/table_test.go

@@ -43,6 +43,7 @@ func TestCreateTableDiff(t *testing.T) {
 		fulltext   int
 		colrename  int
 		constraint int
+		charset    int
 	}{
 		{
 			name: "identical",
@@ -972,7 +973,57 @@ func TestCreateTableDiff(t *testing.T) {
 			cdiff:   "ALTER TABLE `t1` AUTO_INCREMENT 100",
 		},
 		{
-			name:  `change table charset`,
+			name:  "apply table charset",
+			from:  "create table t (id int, primary key(id))",
+			to:    "create table t (id int, primary key(id)) DEFAULT CHARSET = utf8mb4",
+			diff:  "alter table t charset utf8mb4",
+			cdiff: "ALTER TABLE `t` CHARSET utf8mb4",
+		},
+		{
+			name:    "ignore empty table charset",
+			from:    "create table t (id int, primary key(id))",
+			to:      "create table t (id int, primary key(id)) DEFAULT CHARSET = utf8mb4",
+			charset: TableCharsetCollateIgnoreEmpty,
+		},
+		{
+			name:    "ignore empty table charset and collate",
+			from:    "create table t (id int, primary key(id))",
+			to:      "create table t (id int, primary key(id)) DEFAULT CHARSET = utf8mb4 COLLATE utf8mb4_0900_ai_ci",
+			charset: TableCharsetCollateIgnoreEmpty,
+		},
+		{
+			name:    "ignore empty table collate",
+			from:    "create table t (id int, primary key(id))",
+			to:      "create table t (id int, primary key(id)) COLLATE utf8mb4_0900_ai_ci",
+			charset: TableCharsetCollateIgnoreEmpty,
+		},
+		{
+			name:    "ignore empty table charset and collate in target",
+			from:    "create table t (id int, primary key(id)) DEFAULT CHARSET = utf8mb4 COLLATE utf8mb4_0900_ai_ci",
+			to:      "create table t (id int, primary key(id))",
+			charset: TableCharsetCollateIgnoreEmpty,
+		},
+		{
+			name:    "ignore dropped collate",
+			from:    "create table t (id int, primary key(id)) COLLATE utf8mb4_0900_ai_ci",
+			to:      "create table t (id int, primary key(id))",
+			charset: TableCharsetCollateIgnoreEmpty,
+		},
+		{
+			name:    "ignore table charset",
+			from:    "create table t (id int, primary key(id)) DEFAULT CHARSET = utf8",
+			to:      "create table t (id int, primary key(id)) DEFAULT CHARSET = utf8mb4",
+			charset: TableCharsetCollateIgnoreAlways,
+		},
+		{
+			name:  "change table charset",
+			from:  "create table t (id int, primary key(id)) DEFAULT CHARSET = utf8",
+			to:    "create table t (id int, primary key(id)) DEFAULT CHARSET = utf8mb4",
+			diff:  "alter table t charset utf8mb4",
+			cdiff: "ALTER TABLE `t` CHARSET utf8mb4",
+		},
+		{
+			name:  `change table charset and columns`,
 			from:  "create table t (id int primary key, t1 varchar(128) default null, t2 varchar(128) not null, t3 tinytext charset latin1, t4 tinytext charset latin1) default charset=utf8",
 			to:    "create table t (id int primary key, t1 varchar(128) not null, t2 varchar(128) not null, t3 tinytext, t4 tinytext charset latin1) default charset=utf8mb4",
 			diff:  "alter table t modify column t1 varchar(128) not null, modify column t2 varchar(128) not null, modify column t3 tinytext, charset utf8mb4",
@@ -1059,6 +1110,7 @@ func TestCreateTableDiff(t *testing.T) {
 			hints.ConstraintNamesStrategy = ts.constraint
 			hints.ColumnRenameStrategy = ts.colrename
 			hints.FullTextKeyStrategy = ts.fulltext
+			hints.TableCharsetCollateStrategy = ts.charset
 			alter, err := c.Diff(other, &hints)
 
 			require.Equal(t, len(ts.diffs), len(ts.cdiffs))

go/vt/schemadiff/types.go

@@ -88,13 +88,20 @@ const (
 	FullTextKeyUnifyStatements
 )
 
+const (
+	TableCharsetCollateStrict int = iota
+	TableCharsetCollateIgnoreEmpty
+	TableCharsetCollateIgnoreAlways
+)
+
 // DiffHints is an assortment of rules for diffing entities
 type DiffHints struct {
-	StrictIndexOrdering     bool
-	AutoIncrementStrategy   int
-	RangeRotationStrategy   int
-	ConstraintNamesStrategy int
-	ColumnRenameStrategy    int
-	TableRenameStrategy     int
-	FullTextKeyStrategy     int
+	StrictIndexOrdering         bool
+	AutoIncrementStrategy       int
+	RangeRotationStrategy       int
+	ConstraintNamesStrategy     int
+	ColumnRenameStrategy        int
+	TableRenameStrategy         int
+	FullTextKeyStrategy         int
+	TableCharsetCollateStrategy int
 }