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https://issues.apache.org/jira/browse/GORA-401?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15495844#comment-15495844
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Kevin Ratnasekera commented on GORA-401:
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[~lewismc] I faced the same issue when I was implementing the JCache store 
where I wanted preserve/protect the dirty bytes of persistent beans when they 
are putting and getting back from caches. ( Since cache maintains databeans in 
serialized form ) To address this I have explicitly handled persistent bean 
serialization by extending  java.io.Externalizable at 
PersistentBase. Please see [1] where I have introduced public getter/setter for 
dirty bytes ( also discussed in this thread ), at explicit serialization of 
databean I have introduced  logic to preserve dirty bytes [2].

[1] 
https://github.com/apache/gora/blob/master/gora-core/src/main/java/org/apache/gora/persistency/impl/PersistentBase.java#L186-L219
[2] 
https://github.com/apache/gora/blob/master/gora-compiler/src/main/velocity/org/apache/gora/compiler/templates/record.vm#L357-L387

> Serialization and deserialization of Persistent does not hold the entity 
> dirty state from Map to Reduce
> -------------------------------------------------------------------------------------------------------
>
>                 Key: GORA-401
>                 URL: https://issues.apache.org/jira/browse/GORA-401
>             Project: Apache Gora
>          Issue Type: Bug
>          Components: gora-core
>    Affects Versions: 0.4, 0.5
>         Environment: Tested on gora-0.4, but seems logically to hold on 
> gora-0.5. HBase backend.
>            Reporter: Alfonso Nishikawa
>            Assignee: Alfonso Nishikawa
>            Priority: Critical
>              Labels: serialization
>             Fix For: 0.8
>
>         Attachments: GORA-401-tests.patch, GORA-401v1.patch, 
> GORA-401v2.patch, GORA-401v3.patch, GORA-401v4.patch, GORA-401v5.patch
>
>   Original Estimate: 35h
>          Time Spent: 21h
>  Remaining Estimate: 14h
>
> After removing __g__dirty field in GORA-326, dirty field is not serialized. 
> In GORA-321 
> {{[PersistentSerializer|https://github.com/apache/gora/blob/master/gora-core/src/main/java/org/apache/gora/mapreduce/PersistentSerializer.java]}}
>  went from using 
> {{[PersistentDatumWriter|https://github.com/apache/gora/blob/apache-gora-0.3/gora-core/src/main/java/org/apache/gora/avro/PersistentDatumWriter.java](/Reader)}}
>  to Avro's {{SpecificDatumWriter}}, delegating the serialization of the dirty 
> field to Avro (but really not desirable to have that field as a main field in 
> the entities).
> The proposal is to reintroduce the {{PersistentDatumWriter/Reader}} which 
> will serialize the internal fields of the entities.
> This bug affects, for example, Nutch, which loads only some fields in it's 
> phases, serializes entities (from Map to Reduce), and when deserializes finds 
> all fields as "dirty", independently of what fields were modified in the Map, 
> and overwrite all data in datastore (deleting much things: downloaded 
> content, parsed content, etc).
> This effect can be seen in 
> {{TestPersistentSerialization#testSerderEmployeeTwoFields}}, when debuging in 
> {{TestIOUtils#testSerializeDeserialize}}. Proper breakpoints an inspections 
> shows that, entities are "equal" when it's fields are equal. This is fine as 
> "equal" definition, but another test must be added to check that 
> serialization an deserialization keeps the dirty state.



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