[jira] Commented: (OPENJPA-435) Change mapping defaults to assume foreign keys exist for relationships by default

["Willis Blackburn (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/OPENJPA-435?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12914841#action_12914841 ] 

Willis Blackburn commented on OPENJPA-435:
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+1!

It doesn't seem logical to assume that FKs don't exist.

Reason #1:  They usually do!  Let's assume that people using OpenJPA are intelligent and are designing production-quality databases.  Of course they're going to have FKs.

Reason #2:  The strategy of querying the database to discover the FKs seems at odds with the general JPA strategy of declaring the database metadata in code.  We let the code define the database, not vice-versa.

Reason #3:  It leads to the fewest surprises.  Consider:

    OpenJPA assumes FKs don't exist, and they don't:  OK
    OpenJPA assumes FKs don't exist, and they do:  FAIL!
    OpenJPA assumes FKs exist, and they don't:  No worries!
    OpenJPA assumes FKs exist, and they do:  OK



> Change mapping defaults to assume foreign keys exist for relationships by default
> ---------------------------------------------------------------------------------
>
>                 Key: OPENJPA-435
>                 URL: https://issues.apache.org/jira/browse/OPENJPA-435
>             Project: OpenJPA
>          Issue Type: Improvement
>          Components: sql
>    Affects Versions: 0.9.0, 0.9.6, 0.9.7, 1.0.0, 1.0.1, 1.0.2, 1.1.0
>            Reporter: Patrick Linskey
>             Fix For: 1.3.0
>
>
> OpenJPA's current defaults assume that no foreign keys exist. This leads to potentially more optimal SQL ordering, but often also leads to FK constraint violations when obvious FKs exist but are not declared. We should change this default to be more user-friendly, and add a note to our optimization guide as appropriate if there are actions users should take to optimize.

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