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https://issues.apache.org/jira/browse/DERBY-4442?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12780619#action_12780619
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Knut Anders Hatlen commented on DERBY-4442:
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The patch does break some statements that used to work, for instance this:
ij> create table t2(x int generated by default as identity);
0 rows inserted/updated/deleted
ij> insert into t2 values 1 union values default;
ERROR XJ001: Java exception: ': java.lang.NullPointerException'.
However, I don't think this statement should have been accepted in the first
place. VALUES DEFAULT is not accepted in a subquery unless it's part of a
UNION, it seems:
ij> insert into t2 select * from (values default) v;
ERROR 42Y85: The DEFAULT keyword is only allowed in a VALUES clause when the
VALUES clause appears within an INSERT statement.
> Evaluation of default value and identity in an INSERT result set evaluated
> too early.
> -------------------------------------------------------------------------------------
>
> Key: DERBY-4442
> URL: https://issues.apache.org/jira/browse/DERBY-4442
> Project: Derby
> Issue Type: Bug
> Components: SQL
> Reporter: Dag H. Wanvik
> Attachments: always_prn.diff, insert.diff
>
>
> In contrast to generated column, which are evaluated when the next row from
> the result set to be inserted, currently default values and identity columns
> are generated "early", that is as part of avaluating the subquery (SELECT or
> VALUES as the case may be).
> This does not currently cause a user visible bug in Derby, but it lies behind
> DERBY-3 and the effect Bryan observed in DERBY-4.
> Additionally, "early" computation has given rise to much special handling and
> ensuing bugs, cf. DERBY-1644, DERBY-4413, DERBY-4419, DERBY-4425 and others.
> DERBY-4397 requires this fix for correct behaviour with INSERT.
> See also
> https://issues.apache.org/jira/browse/DERBY-4413?focusedCommentId=12769532&page=com.atlassian.jira.plugin.system.issuetabpanels%3Acomment-tabpanel#action_12769532
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