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From "Chris Goodacre (JIRA)" <j...@apache.org>
Subject [jira] Commented: (DERBY-4357) TableFunctions provide no information to limit underlying query
Date Thu, 03 Sep 2009 18:18:57 GMT

    [ https://issues.apache.org/jira/browse/DERBY-4357?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12751117#action_12751117
] 

Chris Goodacre commented on DERBY-4357:
---------------------------------------

Related to Knut's comment (and your reply) about <>, what would be the path to add that
operator and other operators that fall outside of the Orderable interface (e.g. IN and NOT
IN).   Would this mechanism ever support a query like this:

  create function foreignEmployeeTable()
  returns table
  (
      id        int,
      birthDay  date,
      status character(1),
      firstName varchar( 100 ),
      lastName  varchar( 100 )
  )

select lastName from table( foreignEmployeeTable() ) s where status in ('A','L','S')

> TableFunctions provide no information to limit underlying query
> ---------------------------------------------------------------
>
>                 Key: DERBY-4357
>                 URL: https://issues.apache.org/jira/browse/DERBY-4357
>             Project: Derby
>          Issue Type: Improvement
>          Components: SQL
>    Affects Versions: 10.4.1.3, 10.4.2.0, 10.5.1.1, 10.5.2.0, 10.5.3.0
>         Environment: ALL
>            Reporter: Chris Goodacre
>         Attachments: RestrictedTableFunctions.html
>
>
> The API specification for TableFunctions cannot provide information to the implementer
of the TableFunction about the details of the query.  For example: 
> (a) I defined a table function named MyFunction with columns a,b, & c
> (b) I bind the table function properly using the CREATE FUNCTION SQL.
> User executes the following SQL:
> select a,b from table ( MyFunction() ) where c = 123
> Without passing the column list and/or where clause as arguments to the table function,
my implementation can not know that it only needs two of the three columns, and only rows
where c = 123.
> For TableFunctions that are built to integrate distant/legacy data, the cost of the query
can be prohibitive.   It would be better if information regarding the columns in the select
and restrictions from the where clause could be passed to the developer.

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