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From "Feng Honghua (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-8753) Provide new delete flag which can delete all cells under a column-family which have a same designated timestamp
Date Thu, 20 Jun 2013 13:20:20 GMT

    [ https://issues.apache.org/jira/browse/HBASE-8753?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13689229#comment-13689229
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Feng Honghua commented on HBASE-8753:
-------------------------------------

[~lhofhansl] For the backwards-compatibility, when old RS processes the DeleteFamilyVersion
type kv (either written from new client, or the two scenarios you mentioned regarding rolling
restart), the DeleteFamilyVersion can enter ScanDeleteTracker, and its only effect it has
is when no DeleteColumn for null column with the same timestamp as this DeleteFamilyVersion,
this DeleteFamilyVersion can delete the KV (column=null) with the same timestamp (a bit like
the Delete(DeleteVersion) with the same timestamp), and no other side-effect.

In summary: DeleteFamilyVersion masks all the versions with a given timestamp under a CF,
and when an old RS receives it(written from new client, or the two scenarios mentioned regarding
rolling restart), the old RS treats it like it's a Delete(DeleteVersion) for null column.
Nothing else.

I think this side-effect is acceptable. Your opinion?
                
> Provide new delete flag which can delete all cells under a column-family which have a
same designated timestamp
> ---------------------------------------------------------------------------------------------------------------
>
>                 Key: HBASE-8753
>                 URL: https://issues.apache.org/jira/browse/HBASE-8753
>             Project: HBase
>          Issue Type: New Feature
>          Components: Deletes
>            Reporter: Feng Honghua
>         Attachments: HBASE-8753-0.94-V0.patch, HBASE-8753-trunk-V0.patch
>
>
> In one of our production scenario (Xiaomi message search), multiple cells will be put
in batch using a same timestamp with different column names under a specific column-family.

> And after some time these cells also need to be deleted in batch by given a specific
timestamp. But the column names are parsed tokens which can be arbitrary words , so such batch
delete is impossible without first retrieving all KVs from that CF and get the column name
list which has KV with that given timestamp, and then issuing individual deleteColumn for
each column in that column-list.
> Though it's possible to do such batch delete, its performance is poor, and customers
also find their code is quite clumsy by first retrieving and populating the column list and
then issuing a deleteColumn for each column in that column-list.
> This feature resolves this problem by introducing a new delete flag: DeleteFamilyVersion.

>   1). When you need to delete all KVs under a column-family with a given timestamp, just
call Delete.deleteFamilyVersion(cfName, timestamp); only a DeleteFamilyVersion type KV is
put to HBase (like DeleteFamily / DeleteColumn / Delete) without read operation;
>   2). Like other delete types, DeleteFamilyVersion takes effect in get/scan/flush/compact
operations, the ScanDeleteTracker now parses out and uses DeleteFamilyVersion to prevent all
KVs under the specific CF which has the same timestamp as the DeleteFamilyVersion KV to pop-up
as part of a get/scan result (also in flush/compact).
> Our customers find this feature efficient, clean and easy-to-use since it does its work
without knowing the exact column names list that needs to be deleted. 
> This feature has been running smoothly for a couple of months in our production clusters.

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