schemadiff: adding charset/collation tests (#15872)

Signed-off-by: Shlomi Noach <[email protected]>

go/vt/schemadiff/schema_diff_test.go

@@ -294,6 +294,18 @@ func TestSchemaDiff(t *testing.T) {
 			entityOrder:       []string{"t1", "t2", "v2"},
 			instantCapability: InstantDDLCapabilityPossible,
 		},
+		{
+			name: "two identical tables, one with explicit charset, one without",
+			fromQueries: []string{
+				"create table foobar (id int primary key, foo varchar(64) character set utf8mb3 collate utf8mb3_bin)",
+			},
+			toQueries: []string{
+				"create table foobar (id int primary key, foo varchar(64) collate utf8mb3_bin)",
+			},
+			entityOrder:       []string{},
+			instantCapability: InstantDDLCapabilityIrrelevant,
+		},
+
 		{
 			name: "instant DDL possible on 8.0.32",
 			toQueries: []string{

go/vt/schemadiff/table_test.go

@@ -1878,6 +1878,11 @@ func TestCreateTableDiff(t *testing.T) {
 			diff:  "alter table t collate utf8mb4_0900_bin",
 			cdiff: "ALTER TABLE `t` COLLATE utf8mb4_0900_bin",
 		},
+		{
+			name: "ignore identical implicit charset",
+			from: "create table t (id int primary key, v varchar(64) character set utf8mb3 collate utf8mb3_bin)",
+			to:   "create table t (id int primary key, v varchar(64) collate utf8mb3_bin)",
+		},
 		{
 			name:  "normalized unsigned attribute",
 			from:  "create table t1 (id int primary key)",
@@ -2889,6 +2894,11 @@ func TestNormalize(t *testing.T) {
 			from: "create table t (id int signed primary key, v varchar(255) charset utf8mb3 collate utf8_unicode_ci) charset utf8mb3 collate utf8_unicode_ci",
 			to:   "CREATE TABLE `t` (\n\t`id` int,\n\t`v` varchar(255),\n\tPRIMARY KEY (`id`)\n) CHARSET utf8mb3,\n  COLLATE utf8mb3_unicode_ci",
 		},
+		{
+			name: "remove column charset if collation is explicit and implies specified charset",
+			from: "create table t (id int primary key, v varchar(255) charset utf8mb4 collate utf8mb4_german2_ci)",
+			to:   "CREATE TABLE `t` (\n\t`id` int,\n\t`v` varchar(255) COLLATE utf8mb4_german2_ci,\n\tPRIMARY KEY (`id`)\n)",
+		},
 		{
 			name: "correct case table options for engine",
 			from: "create table t (id int signed primary key) engine innodb",