TableFunctions provide no information to limit underlying query
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Key: DERBY-4357
URL: https://issues.apache.org/jira/browse/DERBY-4357
Project: Derby
Issue Type: Improvement
Components: SQL
Environment: ALL
Reporter: Chris Goodacre
Fix For: 10.6.0.0
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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