Home | About | Sematext search-lucene.com search-hadoop.com
 Search Hadoop and all its subprojects:

Switch to Threaded View
HBase, mail # user - What happened in hlog if data are deleted cuased by ttl?


Copy link to this message
-
Re: What happened in hlog if data are deleted cuased by ttl?
Harsh J 2012-08-14, 15:20
Yes, TTL deletions are done only during compactions. They aren't
"Deleted" in the sense of what a Delete insert signifies, but are
rather eliminated in the write process when new
storefiles are written out - if the value being written to the
compacted store has already expired.

On Tue, Aug 14, 2012 at 8:40 PM, yonghu <[EMAIL PROTECTED]> wrote:
> Hi Hars,
>
> Thanks for your reply. If I understand you right, it means the ttl
> deletion will not reflect in log.
>
> On Tue, Aug 14, 2012 at 3:24 PM, Harsh J <[EMAIL PROTECTED]> wrote:
>> Hi Yonghu,
>>
>> A timestamp is stored along with each insert. The ttl is maintained at
>> the region-store level. Hence, when the log replays, all entries with
>> expired TTLs are automatically omitted.
>>
>> Also, TTL deletions happen during compactions, and hence do not
>> carry/need Delete events. When scanning a store file, TTL-expired
>> entries are automatically skipped away.
>>
>> On Tue, Aug 14, 2012 at 3:34 PM, yonghu <[EMAIL PROTECTED]> wrote:
>>> My hbase version is 0.92. I tried something as follows:
>>> 1.Created a table 'test' with 'course' in which ttl=5.
>>> 2. inserted one row into the table. 5 seconds later, the row was deleted.
>>> Later when I checked the log infor of 'test' table, I only found the
>>> inserted information but not deleted information.
>>>
>>> Can anyone tell me which information is written into hlog when data is
>>> deleted by ttl or in this situation, no information is written into
>>> the hlog. If there is no information of deletion in the log, how can
>>> we guarantee the data recovered by log are correct?
>>>
>>> Thanks!
>>>
>>> Yong
>>
>>
>>
>> --
>> Harsh J

--
Harsh J