[IGNITE-14066] JDBC DatabaseMetaData::getColumns reports REAL column type as FLOAT

• Type: Bug
• Status: Open
• Priority: Major
• Resolution: Unresolved
• Affects Version/s: 2.9.1
• Component/s: jdbc
• Ignite Flags: Docs Required, Release Notes Required
• Assignee: Unassigned
• Reporter: Lukas Eder
• Created: 26/Jan/21 15:53
• Updated: 26/Jan/21 15:53

Description

Create a table containing a REAL column:

create table t (i int primary key, r real);

Now read the meta data from DatabaseMetaData::getColumns:

try (ResultSet rs = c.getMetaData().getColumns(null, "PUBLIC", "T", null)) {
  while (rs.next())
    System.out.println(rs.getString("6"));
}

The reported type name is FLOAT, not REAL. The documentation lists no such type, although it does say that REAL is mapped to Java/JDBC "float": https://ignite.apache.org/docs/latest/sql-reference/data-types#real

JDBC's java.sql.Types class doesn't specify the precision of each of these types, but the SQL standard <approximate numeric type> definition specifies REAL as "single precision" and DOUBLE (PRECISION) as "double precision", whereas FLOAT can be used with an explicit precision, e.g. FLOAT.

This is particularly problematic because if I create the table with an actual "FLOAT" type (which isn't documented):

create table t (i int primary key, r float);

Then the JDBC driver reports DOUBLE for the above program. This makes sense according to the SQL standard and also according to my experience with most other RDBMS. A FLOAT type in SQL is really a Java double, not a Java float.

So, in my opinion, JDBC should report REAL, not FLOAT.