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https://issues.apache.org/jira/browse/DERBY-716?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12476187
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Rick Hillegas commented on DERBY-716:
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Thanks, Dan. I think what has me confused here is the wiki page's reference to
Part 13, section 8.5. That section deals with ARRAY types. I see that 8.6
addresses the case of MULTISET return types. My reading (of Part 13, Section
9.8, syntax rule 12 and Part 13, Section 8.6) is that the routine resolution
on the wiki page addresses the case when PARAMETER STYLE JAVA is specified.
My itch is to re-enable the ResultSet style VTIs, which you agree are elegant
and powerful. Here's a proposal:
1) We introduce a new kind of parameter style, say PARAMETER STYLE DERBY. We
can sand down the name of this style later on.
2) For a first rev, the customer must specify PARAMETER STYLE DERBY when they
declare a table-returning function.These methods resolve to static methods
which return ResultSets.
3) Later on, someone who has the itch can implement PARAMETER STYLE JAVA and
the kinds of method signatures described in the wiki page.
4) Perhaps someone can contribute some machinery which will wrap DERBY-style
methods inside JAVA-style ones and vice-versa.
I think this proposal
A) Enables a powerful programming model which distinguishes Derby
B) Nevertheless allows later implementation of the ANSI method-style for people
who are interested in migrating table-functions to/from other databases.
> Re-enable VTIs
> --------------
>
> Key: DERBY-716
> URL: https://issues.apache.org/jira/browse/DERBY-716
> Project: Derby
> Issue Type: New Feature
> Components: SQL
> Reporter: Rick Hillegas
>
> Cloudscape used to expose Virtual Table Interfaces, by which any class which
> implemented ResultSet could be included in a query's FROM list. Derby still
> exposes a number of these VTIs as diagnostic tools. However, Derby now
> prevents customers from declaring their own VTIs. The parser raises an error
> if a VTI's package isn't one of the Derby diagnostic packages.
> This is a very powerful feature which customers can use to solve many
> problems. We should discuss the reasons that it was disabled and come up with
> a plan for putting this power back into our customers' hands.
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