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https://issues.apache.org/jira/browse/DERBY-3341?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12574666#action_12574666
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Rick Hillegas commented on DERBY-3341:
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The bind tree looks correct to me. The compiler has the correct understanding
of what SQL types are supposed to correspond to the columns in the user-coded
ResultSet. From one point of view, you could say that the problem is that the
user has lied: At DDL time the user declared that a string column in a table
function has a maximum length, but the actual user-coded implementation of the
ResultSet does not obey this contract. I think that, technically, the behavior
is undefined right now because ANSI does not have rules about what happens if a
Derby-style table function returns an oversized string.
The current behavior is unattractive. We are free to define what we think the
correct behavior should be--and then we should document that correct behavior.
One approach would be to throw a SQLException if the ResultSet does not fulfill
the declared contract. However, I think that silently truncating oversized
strings would be more useful. The current proposal seems fine:
If the customer declares that a string column in a Table Function has a maximum
length, and the underlying user-coded ResultSet returns oversized strings, then
Derby should silently truncate those strings to the declared maximum length by
chopping off trailing characters.
> TABLE FUNCTION returning CHAR values does not return a correct value if the
> Java ResultSet class returns a value less than the length of the defined CHAR.
> ----------------------------------------------------------------------------------------------------------------------------------------------------------
>
> Key: DERBY-3341
> URL: https://issues.apache.org/jira/browse/DERBY-3341
> Project: Derby
> Issue Type: Bug
> Components: SQL
> Reporter: Daniel John Debrunner
> Fix For: 10.4.0.0
>
> Attachments: derby_3341_test.txt
>
>
> Defining a column in the returned type as CHAR(10) requires that the returned
> value be of length 10 characters.
> Defining a table function with a return type of:
> returns TABLE column0 char( 10 ), column1 char( 10 ))
> seems to just return whatever the Java ResultSet implementation handed it.
> My guess this is true for all variable length types, no casting of the value
> occurs when it is returned to the SQL domain.
> Java single value functions and procedure out parameters do perform any
> required casting to ensure the value is of the declared type.
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