Rick Hillegas created DERBY-6070:
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Summary: Document Derby's JDBC 4.2 implementation
Key: DERBY-6070
URL: https://issues.apache.org/jira/browse/DERBY-6070
Project: Derby
Issue Type: Improvement
Components: Documentation
Affects Versions: 10.10.0.0
Reporter: Rick Hillegas
We may want to document the following specifics of Derby's JDBC 4.2
implementation:
--- DatabaseMetaData.getMaxLogicalLobSize() ---
This is a new method added by JDBC 4.2. The javadoc for this method is terse:
"long getMaxLogicalLOBSize()
throws SQLException
Retrieves the maximum number of bytes this database allows for the logical size
for a LOB.
Returns:
the maximum number of bytes allowed; a result of zero means that there is
no limit or the limit is not known
Throws:
SQLException - if a database access error occurs"
Derby returns 0. The meaningful limits on Derby's BLOB and CLOB datatypes are
documented in the datatype section of the Reference Manual.
--- SQLType ---
JDBC 4.2 introduces a new datatype identifier (java.sql.SQLType) to help
databases describe datatypes which don't appear in the ANSI/ISO SQL Standard.
The idea is that databases with non-standard types can provide their own
implementations of SQLType. JDBC 4.2 also supplies its own implementation
(java.sql.JDBCType) which provides an enum for each of the type ids in
java.sql.Types.
Derby doesn't expose any datatypes which aren't represented by JDBCType enums
and so Derby doesn't need to provide its own implementation of SQLType.
Overloads with SQLType arguments have been added to various interfaces,
alongside the existing methods which take int type ids from java.sql.Types. The
affected interfaces are: CallableStatement, PreparedStatement, and ResultSet.
On Derby, these methods raise an "unsupported datatype" exception (SQLState
0A000) if the caller passes in a bad SQLType, namely:
1) A SQLType from a foreign database. That is a SQLType which isn't one of the
JDBCType enums.
2) A JDBCType enum whose corresponding int type id (from java.sql.Types) isn't
supported by Derby. The supported int type ids are documented in the datatype
section of the Reference Manual. The JDBCType enums have the same names as
their corresponding int ids in java.sql.Types.
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