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https://issues.apache.org/jira/browse/DERBY-3609?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12587198#action_12587198
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Bernt M. Johnsen commented on DERBY-3609:
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Formally, Derby does not support getGeneratedKeys since
DatabaseMetaData.supportsGetGeneratedKeys() returns false. However,
Statement.getGeneratedKeys() is partially implemented, and behaves very similar
to IDENTITY_VAL_LOCAL() since it will only return a meaningful result when an
single row insert is done with INSERT...VALUES. However, you have to specify
Statement.RETURN_GENERATED_KEYS, e.g. like this
s.executeUpdate("insert into t(i) values (1)",
Statement.RETURN_GENERATED_KEYS);
I agree that returning null from getGeneratedKeys is not according to spec and
that an ResultSet with no rows would be more appropriate. Also, the docs for
"Autogenerated keys" in the ref.man. would need a rewrite to be comprehendable.
Another quirk is that getGeneratedKeys() will return a resultset with one row
with an SQL null-value if the statement was an insert of multiple rows, and not
like DENTITY_VAL_LOCAL() which returns the value of the generated key from the
last single-row insert.
> Wrong functionality of auto-generated keys support
> --------------------------------------------------
>
> Key: DERBY-3609
> URL: https://issues.apache.org/jira/browse/DERBY-3609
> Project: Derby
> Issue Type: Bug
> Components: JDBC
> Affects Versions: 10.3.2.1
> Environment: N/A
> Reporter: Oleksandr Alesinskyy
>
> Currently support for autogeneration key retrieval in JDBC driver
> (java.sql.Statement) relies on IDENTITY_VAL_LOCAL function, which means that
> for multi-row INSERT... VALUES statements as well as for INSERT...AS SELECT
> statement wrong result are returned (key generated of last executed
> single-row INSERT...VALUES statement or NULL otherwise). While this
> functionality is documented in the Reference description of
> IDENTITY_VAL_LOCAL it is not so clearly documented in "autogenerated keys"
> subchapter of JDBC 3.0 Features (the only vague hint is "Calling
> ResultSet.getMetaData on the ResultSet object returned by getGeneratedKeys
> produces a ResultSetMetaData object that is similar to that returned by
> IDENTITY_VAL_LOCAL.").
> Moreover, as far as I understant it diverge from JDBC specification. IMHO or
> this functionality shal lbe implemented completely, or exception shall be
> thrown if for given statement functionality is not supported (e.g. "Feature
> not supported").
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