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From "ASF subversion and git services (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (AIRAVATA-2872) registry-refactoring: OpenJPA doesn't persist setting a field to null
Date Tue, 06 Nov 2018 16:48:00 GMT

    [ https://issues.apache.org/jira/browse/AIRAVATA-2872?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16676982#comment-16676982
] 

ASF subversion and git services commented on AIRAVATA-2872:
-----------------------------------------------------------

Commit 2c01b94181be962f62bfca11c44a375745b00b45 in airavata's branch refs/heads/develop from
[~marcuschristie]
[ https://gitbox.apache.org/repos/asf?p=airavata.git;h=2c01b94 ]

AIRAVATA-2872 Adding NOT NULL to foreign key columns

Also cleaning up, syncing up SQL files. I removed the derby SQL files
from test/resources since we don't need a separate copy from the ones in
main/resources and having a single copy should reduce confusion.


> registry-refactoring: OpenJPA doesn't persist setting a field to null
> ---------------------------------------------------------------------
>
>                 Key: AIRAVATA-2872
>                 URL: https://issues.apache.org/jira/browse/AIRAVATA-2872
>             Project: Airavata
>          Issue Type: Bug
>          Components: Registry API
>            Reporter: Marcus Christie
>            Assignee: Marcus Christie
>            Priority: Major
>
> In OpenJPA, the default handling of null values on detached instances is to treat them
as "unloaded" when merging them, meaning it treats them as if they are simply missing instead
of treating them as having been set to null. That is, it skips over null value and doesn't
update the corresponding fields on the persistent instances to have a null value.
> See https://stackoverflow.com/a/2569417/1419499
> See also official docs: http://openjpa.apache.org/builds/2.4.3/apache-openjpa/docs/ref_guide_remote.html#ref_guide_detach,
however it's hard to understand how to make use of this in our context.
> See also this discussion http://openjpa.208410.n2.nabble.com/null-values-not-updating-td3224059.html
> I traced the OpenJPA code to these lines in VersionAttachStrategy:
> {code:java}
>         int detach = (isNew) ? DETACH_ALL : broker.getDetachState();
>         FetchConfiguration fetch = broker.getFetchConfiguration();
>         try {
>             FieldMetaData[] fmds = sm.getMetaData().getFields(); 
>             for (int i = 0; i < fmds.length; i++) {
>                 switch (detach) {
>                     case DETACH_ALL:
>                         attachField(manager, toAttach, sm, fmds[i], true);
>                         break;
>                     case DETACH_FETCH_GROUPS:
>                         if (fetch.requiresFetch(fmds[i]) 
>                             != FetchConfiguration.FETCH_NONE)
>                             attachField(manager, toAttach, sm, fmds[i], true);
>                         break;
>                     case DETACH_LOADED:
>                         attachField(manager, toAttach, sm, fmds[i], false);
>                         break;
>                 }
>             }
>         } finally {
> {code}
> The detach state is {{DETACH_LOADED}} which causes OpenJPA to treat nulls as unloaded
and thus it skips merging those values in.
> I think with a configuration change we can get this to work, but it's not obvious what
all the flags mean, so this will take some research.
> One other question I have, is how did this work before. It would be worth checking to
see how the old registry code had configured OpenJPA.



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