[DERBY-6849] Statement.RETURN_GENERATED_KEYS returns a 1 row result set even if there are no auto-generated fields - ASF JIRA

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Details

Type: Bug
Status: Open
Priority: Major
Resolution: Unresolved
Affects Version/s: 10.9.1.0
Fix Version/s: None
Component/s: JDBC
Labels:
None

Description

If:
1) A JDBC INSERT statement is executed, with Statement.RETURN_GENERATED_KEYS enabled, and
2) A call is then made to Statement.getGeneratedKeys, and
3) The table which was inserted into has NO generated columns,

then getGeneratedKeys() returns a ResultSet object with a single row in it.

This behavior seems incorrect; it seems that the correct behavior
would be to return a ResultSet object which has NO rows in it, so
that ResultSet.next() returns FALSE the first time it is called.

I have a very simple table:

    CREATE TABLE images (
      url varchar(1000) NOT NULL,
      image blob NOT NULL,
  
      CONSTRAINT images_url PRIMARY KEY (url)
    );

No auto-generated fields. However when I do an insert, JDBC tells me there are auto-generated keys (rs.next() does not return false and a LONG value is returned):

      try(PreparedStatement statement = connection.prepareStatement(sql, Statement.RETURN_GENERATED_KEYS)) {
        setParameters(parameterValues, statement);

        statement.execute();

        try(ResultSet rs = statement.getGeneratedKeys()) {
          if(rs.next()) {
            return rs.getObject(1);
          }

          return null;
        }
      }
      catch(SQLException e) {
        throw new DatabaseException(this, sql + ": " + parameters, e);
      }

This sounds like a bug to me. For comparison, PostgreSQL does not have the same behaviour.