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From "Rick Hillegas (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (DERBY-3155) Support for SQL:2003 MERGE statement
Date Fri, 24 Jan 2014 19:50:38 GMT

     [ https://issues.apache.org/jira/browse/DERBY-3155?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Rick Hillegas updated DERBY-3155:
---------------------------------

    Attachment: derby-3155-19-aa-forbidSubqueriesInMatchedClauses.diff

Attaching derby-3155-19-aa-forbidSubqueriesInMatchedClauses.diff. This patch forbids subqueries
in the WHEN [ NOT ] MATCHED clauses of MERGE statements. I am running tests now.

The SQL Standard allows subqueries in the WHEN [ NOT ] MATCHED clauses of MERGE statements.
However, these subqueries break code-generation. That's because we don't completely optimize
the dummy INSERT/UPDATE/DELETE statements which we cook up in order to compile the WHEN [
NOT ] MATCHED clauses. If we improve the MERGE statement so that the dummy statements are
completely optimized, then we can consider allowing subqueries in these clauses.

I will record this limitation in the functional spec and I will create an enhancement request
for lifting this limitation later on.

Touches the following files:

--------------

M       java/engine/org/apache/derby/impl/sql/compile/MatchingClauseNode.java

The code to forbid these subqueries.

--------------

M       java/engine/org/apache/derby/loc/messages.xml
M       java/shared/org/apache/derby/shared/common/reference/SQLState.java

A new error message for this limitation.

--------------

M       java/testing/org/apache/derbyTesting/functionTests/tests/lang/MergeStatementTest.java

New test cases.


> 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: MergeStatement.html, MergeStatement.html, MergeStatement.html, 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-3155-03-ag-backingStoreHashtableWithRowLocation.diff,
derby-3155-03-ah-backingStoreHashtableWithRowLocation.diff, derby-3155-04-ae-deleteAction.diff,
derby-3155-04-af-deleteAction.diff, derby-3155-05-aa-triggerTransitionTableAsTarget.diff,
derby-3155-06-aa-triggerTransitionTableAsSource.diff, derby-3155-07-ad-insertAction.diff,
derby-3155-08-ah-updateAction.diff, derby-3155-09-aa-correlationNames.diff, derby-3155-10-aa-correlationNames.diff,
derby-3155-11-ab-beforeTriggersCantFireMerge.diff, derby-3155-12-aa-canOmitInsertColumnList.diff,
derby-3155-13-aa-allowSystemAndTempTables.diff, derby-3155-14-aa-replaceCorrelationNamesOnLeftSideOfSETclauses.diff,
derby-3155-15-aa-replumbMergeResultSetCleanup.diff, derby-3155-16-aa-treatCurrentRowLocationNodeLikeBaseColumnNode.diff,
derby-3155-17-aa-serializingRowLocations.diff, derby-3155-18-aa-basicView.diff, derby-3155-19-aa-forbidSubqueriesInMatchedClauses.diff
>
>
> 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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