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https://issues.apache.org/jira/browse/DERBY-672?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13610382#comment-13610382
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Rick Hillegas commented on DERBY-672:
-------------------------------------
Thanks for buddy-testing user-defined aggregates, Dag. Here are responses to
questions you posed on this wiki page:
http://wiki.apache.org/db-derby/TenTenOneBuddyTesting
----------------------
>* Currently, our docs say:
>
> "An unqualified UDA name may not be the name of an aggregate defined in part
> 2 of the SQL Standard, section 10.9:
>
> ANY..
>
> But even when name is qualified, I see:
>
> ij> create derby aggregate app.ANY for int returns int external name
> 'foo.Agg';
> ERROR 42X01: Syntax error: Encountered "ANY" at line 1, column 28.
>
> I need to quote it:
>
> ij> create derby aggregate app."ANY" for int returns int external name
> 'foo.Agg';
> 0 rows inserted/updated/deleted
>
> Code or doc correct?
The wording in the Reference Manual could be improved. Logged DERBY-6116 to
track this.
----------------------
>*
>
> "In general, UDAs live in the same namespace as one-argument user-defined
> functions (see CREATE FUNCTION statement)."
>
> But ij doesn't show aggregates:
>
> ij> create function app."ANY" (i int) returns int parameter style java
> language java external name 'foo.bar';
>
> ERROR X0Y87: There is already an aggregate or function with one argument
> whose name is 'APP'.'ANY'.
>
> ij> show functions in app;
> FUNCTION_SCHEM|FUNCTION_NAME |REMARKS
>
>
> -------------------------------------------------------------------------------
> 0 rows selected
I think what's missing here is a "show aggregates" command. Logged DERBY-6119
to track this.
----------------------
>* checked simple int aggregator: found agg class could not be static nested
>class in another(?)
>
> Expected or pilot error? If expected, why? document? Currently we say:
>
> "The !ClassNameString is a single-quoted string. It is the full name of a
> Java class which implements the org.apache.derby.agg.Aggre>gator interface."
I believe that the problem here is that a period rather than a dollar sign was
used in the name of the nested class in the "external name" clause. This gotcha
trips up a lot of people and indicates that we need to provide some more advice
in the Reference Manual. Logged DERBY-6120 to track this issue.
----------------------
>* The merge method wasn't used in my simple example. When is it used?
>
> If only needed in compex queries, we might want to warn the user on how to
> construct test cases to debug it...
This method is called when Derby has to spill intermediate results to disk (and
retrieve them later) when processing a grouped aggregate with a large number of
groups. I have added this explanation to the javadoc for Aggregator.merge() via
patch derby-672-23-aa-improveJavadocForAggregator.merge.diff.
While verifying this behavior, I tripped across a problem in the test class
ModeAggregator: its state was not serializable. I corrected that problem via
patch derby-672-22-aa-makeModeAggregateStateSerializable.diff. This prompted me
to log an issue for beefing up the UDA documentation with the advice that all
of the state of a UDA must be serializable: DERBY-6127.
----------------------
>* In the GRANT-statement refman page, we are inconsisten when it comes to
>explaining
>
> identifiers (seen when looking at GRANT USAGE of aggregates): "table-Name"
> occurences are linked to a section explainig them (rre>ftablename.html), but
> UDA names are defined in-lined as
>
> GRANT USAGE ON DERBY AGGREGATE [ schemaName. ] SQL92Identifier TO
> grantees
>
> In a third variant,
>
> GRANT EXECUTE ON { FUNCTION | PROCEDURE } routine-designator TO grantees
>
> routine-designator is defined locally as
>
> routine-designator { function-name | procedure-name }
>
> without links to what "function-name" or "procedure-name" might look like.
> It would be good to harmonize the latter two forms to> a central definition
> as for "table-Name".
>
> Finally, I noted that the definition page for SchemaName doesn't link to
> the SQL92Identifier page...
Logged DERBY-6121 to track this issue.
> Re-enable user defined aggregates
> ---------------------------------
>
> Key: DERBY-672
> URL: https://issues.apache.org/jira/browse/DERBY-672
> Project: Derby
> Issue Type: Improvement
> Components: SQL
> Reporter: Rick Hillegas
> Assignee: Rick Hillegas
> Attachments: d672-no-exceptions.diff, derby-672-01-aa-ddl.diff,
> derby-672-02-ac-nonDistinct.diff, derby-672-03-aa-distinct.diff,
> derby-672-03-ab-distinct.diff, derby-672-04-aa-fixJSR169test.diff,
> derby-672-05-aa-java7testOrderProblem.diff, derby-672-06-aa-grantRevoke.diff,
> derby-672-07-aa-fixJSR169again.diff, derby-672-08-aa-fixJSR169yetAgain.diff,
> derby-672-09-ab-udtAggregates.diff, derby-672-10-af-typeBounds.diff,
> derby-672-11-aa-tests.diff, derby-672-11-ab-tests.diff,
> derby-672-12-aa-implicitCasts.diff, derby-672-13-aa-differentReturnType.diff,
> derby-672-14-aa-collations.diff, derby-672-15-aa-setCollation.diff,
> derby-672-16-aa-forbidInGroupBy.diff, derby-672-17-aa-moreTests.diff,
> derby-672-18-aa-udaInJar.diff, derby-672-19-aa-precisionChecks.diff,
> derby-672-20-aa-exactBounds.diff, derby-672-21-aa-typeDependencies.diff,
> derby-672-22-aa-makeModeAggregateStateSerializable.diff,
> derby-672-23-aa-improveJavadocForAggregator.merge.diff,
> UserDefinedAggregates.html, UserDefinedAggregates.html,
> UserDefinedAggregates.html, UserDefinedAggregates.html
>
>
> Nicolas Dufour in an email thread titled "functions and list" started on
> November 2, 2005 requests the ability to create user defined aggregates.
> This functionality used to be in Cloudscape. It was disabled presumably
> because it was considered non-standard. However, most of the machinery needed
> for this feature is still in the code. We should re-enable user defined
> aggregates after we agree on acceptable syntax.
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