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https://issues.apache.org/jira/browse/GORA-391?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Alfonso Nishikawa reassigned GORA-391:
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Assignee: (was: Alfonso Nishikawa)
> Arrays persisted in HBase don't shrink automatically
> ----------------------------------------------------
>
> Key: GORA-391
> URL: https://issues.apache.org/jira/browse/GORA-391
> Project: Apache Gora
> Issue Type: Bug
> Components: gora-hbase
> Affects Versions: 0.4, 0.5
> Reporter: Alfonso Nishikawa
> Priority: Minor
> Labels: arrays, maps
> Fix For: 1.0
>
>
> Fields defined as arrays can grow and be updated, but don't shrink when an
> element is deleted.
> See the code involved:
> [https://github.com/apache/gora/blob/master/gora-hbase/src/main/java/org/apache/gora/hbase/store/HBaseStore.java#L312]
> The workaround is:
> # Define the field as a nullable array: ['null', ...array...]
> # Set the field to null and persist -> the array will be deleted
> # Set the field to the new array and persist -> the array will be persisted
> with the new size
> Comment from Renato:
> bq.You are right, the array can not be shrinked at the moment and yes, it is
> wrong having to write the whole array back if you just want to change a
> single element. The column qualifier used for each item is the original index
> that means if your original array had 10 elements, then you'd have 10 column
> qualfiers to store those 10 items. But if then you delete the third element,
> Gora will end up with 9 actual elements (without the third), but there will
> be a 10th element inside HBase :( and when modifying a specific element, we
> will end up rewriting all of the elements :( Maybe we should do the same
> thing, we do with the maps and rewrite them all into HBase. At least it will
> work correctly.
> Maybe the best solution would be an adaptative persistency: if a big
> percentage of the field is persisted, overwrite everything. If a small
> percentage of the field is persisted, update in a diff maner (addings,
> deletions, updates). This proposed approach seems too much complex, so the
> solution to implement is the one found in maps: delete all elements and write
> them again.
> {panel:bgColor=#FFFFCE} (!) This will be horrible with arrays with big
> elements and only one update, but it is the same as it is being done by now.
> Same for maps. {panel}
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