Hi Just to add on, The HLog is just an edit log. Any transaction updates( Puts/Deletes) are just added to HLog. It is the Scanner that takes care of the TTL part which is calculated from the TTL configured at the column family(Store) level.
Regards Ram > -----Original Message----- > From: Harsh J [mailto:ha...@cloudera.com] > Sent: Tuesday, August 14, 2012 8:51 PM > To: user@hbase.apache.org > Subject: Re: What happened in hlog if data are deleted cuased by ttl? > > 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 <yongyong...@gmail.com> 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 <ha...@cloudera.com> 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 <yongyong...@gmail.com> > 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
