ColumnDiff takes Environment. When a column specifies a collation wit…

…hout a charset, we use Envronment to autopopulate the charset, or return an error what that is not possible

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

go/vt/schemadiff/diff_test.go

@@ -209,6 +209,16 @@ func TestDiffTables(t *testing.T) {
 				TableCharsetCollateStrategy: TableCharsetCollateIgnoreAlways,
 			},
 		},
+		{
+			name: "error on unknown collation",
+			from: "create table t (a varchar(64) COLLATE latin1_nonexisting) default charset=utf8mb4",
+			to:   "create table t (a varchar(64) CHARACTER SET latin1 COLLATE latin1_bin)",
+			hints: &DiffHints{
+				AlterTableAlgorithmStrategy: AlterTableAlgorithmStrategyCopy,
+				TableCharsetCollateStrategy: TableCharsetCollateIgnoreAlways,
+			},
+			isError: true,
+		},
 		{
 			name:     "changing table level defaults with column specific settings",
 			from:     "create table t (a varchar(64) CHARACTER SET latin1 COLLATE latin1_bin) default charset=latin1",

go/vt/schemadiff/table.go

@@ -1575,7 +1575,7 @@ func (c *CreateTableEntity) diffColumns(alterTable *sqlparser.AlterTable,
 		t2ColEntity := NewColumnDefinitionEntity(t2Col)
 
 		// check diff between before/after columns:
-		modifyColumnDiff, err := t1ColEntity.ColumnDiff(t2ColEntity, t1cc, t2cc)
+		modifyColumnDiff, err := t1ColEntity.ColumnDiff(c.Env, t2ColEntity, t1cc, t2cc)
 		if err != nil {
 			return err
 		}