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https://issues.apache.org/jira/browse/DERBY-3155?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Rick Hillegas updated DERBY-3155:
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Attachment: derby-3155-04-ae-deleteAction.diff
Attaching derby-3155-04-ae-deleteAction.diff. This patch adds code-generation
and execution support for the DELETE actions of MERGE statements. With this
patch I am able to successfully use a MERGE statement to DELETE rows from a
table. Cascaded foreign keys and DELETE trigger actions are handled correctly.
I have only been able to test this functionality with search conditions which
cause the optimizer to pick a nested loop strategy for the driving left join of
the MERGE statement. This patch will need to be adjusted after the review of
derby-3155-03-af-backingStoreHashtableWithRowLocation.diff is done and that
functionality is committed. However, I am attaching this patch now just in case
my laptop suffers a disaster in the meantime.
Even after adjustment, the DELETE functionality will need more work,
particularly in the areas of permissions checking and dependency tracking.
For people who are interested in a preliminary peek at the implementation, the
best place to start is the header comment on MergeNode.
> Support for SQL:2003 MERGE statement
> ------------------------------------
>
> Key: DERBY-3155
> URL: https://issues.apache.org/jira/browse/DERBY-3155
> Project: Derby
> Issue Type: Improvement
> Components: SQL
> Reporter: Trejkaz
> Assignee: Rick Hillegas
> Labels: derby_triage10_10
> Attachments: derby-3155-01-ac-grammar.diff,
> derby-3155-02-ag-fixParserWarning.diff,
> derby-3155-03-ae-backingStoreHashtableWithRowLocation.diff,
> derby-3155-03-af-backingStoreHashtableWithRowLocation.diff,
> derby-3155-04-ae-deleteAction.diff, MergeStatement.html, MergeStatement.html,
> MergeStatement.html
>
>
> A relatively common piece of logic in a database application is to check for
> a row's existence and then either update or insert depending on its existence.
> SQL:2003 added a MERGE statement to perform this operation. It looks like
> this:
> MERGE INTO table_name USING table_name ON (condition)
> WHEN MATCHED THEN UPDATE SET column1 = value1 [, column2 = value2 ...]
> WHEN NOT MATCHED THEN INSERT column1 [, column2 ...] VALUES (value1 [,
> value2 ...])
> At the moment, the only workaround for this would be to write a stored
> procedure to do the same operation, or to implement the logic client-side.
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