avoid use of char(n) types on MySQL

MySQL strips trailing space characters from char(n) columns,
which is very bad, because we use char(1) for storing Java
char values.

We can sort-of compensate for this in CharacterJavaType,
but it's ugly and fragile to do it that way.

Signed-off-by: Gavin King <[email protected]>

Author: gavinking

hibernate-core/src/main/java/org/hibernate/dialect/MySQLDialect.java

@@ -268,9 +268,12 @@ protected String columnType(int sqlTypeCode) {
 
 			case NUMERIC -> columnType( DECIMAL ); // it's just a synonym
 
+			// MySQL strips space characters from any value stored in a char column, which
+			// is especially pathological in the case of storing characters in char(1)
+			case CHAR -> "varchar($l)";
+
 			// on MySQL 8, the nchar/nvarchar types use a deprecated character set
-			case NCHAR -> "char($l) character set utf8mb4";
-			case NVARCHAR -> "varchar($l) character set utf8mb4";
+			case NCHAR, NVARCHAR -> "varchar($l) character set utf8mb4";
 
 			// the maximum long LOB length is 4_294_967_295, bigger than any Java string
 			case BLOB -> "longblob";