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https://issues.apache.org/jira/browse/DERBY-6742?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14138455#comment-14138455
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ASF subversion and git services commented on DERBY-6742:
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Commit 1625884 from [~mamtas] in branch 'code/trunk'
[ https://svn.apache.org/r1625884 ]
CERBY-6414(Incorrect handling when using an UPDATE to SET an identity column to
DEFAULT)
I have created DERBY-6742 for JDBC part of this feature so we can generate auto
generated resultset for an update statement updating generated columns. This
implementation is supported through Statement.RETURN_GENERATED_KEYS flag.
Junit tests for this feature are in GeneratedColumnsTest.java. Upgrade tests
are in Changes10_12.java. Upgrade test shows that a soft upgrade from pre-10.11
will not support update of generated columns using DEFAULT but 10.11 to trunk
soft upgrade will allow it. This is because starting 10.11, we have started
using sequence generator to create unique ids. If we want to support updating
of idetity columns for pre-10.11 releases, we will need to maintain the code
for old way of generating unique ids. In order to avoid that, this feature is
available to only 10.11 db during soft upgrade.
For UPDATE of identity column to work in the MERGE sql, we need to make changes
to MERGE code(DERBY-6743). MERGE already has required code for insert putting
DEFAULT in generated columns. Implementation needs to be added for update
putting DEFAULT in generated columns in case of MERGE. In the mean time, I have
renamed existing junit test test_015_bug_6414 to atest_015_bug_6414 in
MergeStatementTest.java so we do not run into failures.
Some detail about the part of the implementation that was tricky for DERBY-6414.
The existing code was originally written to handle inserting values in identity
columns using DEFAULT. In case of insert, InsertResultSet uses
ColumnDescriptors in resultDescription to find the type of the generated
columns. This data structure holds the column descriptors of all the columns in
the table. All the columns are in this data structure because even though
INSERT statement may not explicitly assign a value to each and every column in
the table, all the columns end up getting some value in them through an INSERT
statement. The code in InsertResultSet.initializeAIcache method relies on
availability of all the columns type information. But in case of Update,
resultDescription does not include all the columns in the table. It only has
the columns being touched by the Update statement(the rest of the columns in
the table will retain their original values), and for each of those touched
columns, it has a duplicate entry in resultDescription in order to have before
and after values for the changed column values. This difference in array
content of resultDescription requires us to have separate implementation of
initializeAIcache method for insert and update.
> For update statement, collect generated keys if
> Statement.RETURN_GENERATED_KEYS flag is supplied to the JDBC call.
> ------------------------------------------------------------------------------------------------------------------
>
> Key: DERBY-6742
> URL: https://issues.apache.org/jira/browse/DERBY-6742
> Project: Derby
> Issue Type: Improvement
> Components: JDBC
> Affects Versions: 10.12.0.0
> Reporter: Mamta A. Satoor
> Assignee: Mamta A. Satoor
>
> DERBY-6414 is providing SQL support to update identity columns using DEFAULT
> keyword. This jira will look into collecting generated keys if
> Statement.RETURN_GENERATED_KEYS flag is supplied to the JDBC call for an
> UPDATE sql.
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