[jira] Commented: (DERBY-3609) Wrong functionality of auto-generated keys support

["Bernt M. Johnsen (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/DERBY-3609?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12587198#action_12587198 ] 

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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