Sorry for that. I didn't use the right parameter. Now I get the point. regards!
Yong On Wed, Aug 22, 2012 at 10:49 AM, Harsh J <ha...@cloudera.com> wrote: > Hey Yonghu, > > You are right that TTL "deletions" (it isn't exactly a delete, its > more of a compact-time skip wizardry) do not go to the HLog as > "events". Know that TTLs aren't applied "per-cell", they are applied > on the whole CF globally. So there is no such thing as a TTL-write or > a TTL-delete event. In fact, the Region-level Coprocessor too has no > hooks for "TTL-events", as seen at > http://hbase.apache.org/apidocs/org/apache/hadoop/hbase/coprocessor/RegionObserver.html, > for this doesn't happen on triggers. > > What you say about the compaction part is wrong however. Compaction > too runs a regular store-file scanner to compact, and so does the > regular Scan operation, to read (Both use the same file scanning > mechanism/code). So there's no difference in how compact or a client > scan handle TTL-expired row values from a store file, when reading it > up. > > I also am not able to understand what your sample shell command list > shows. As I see it, its shown that the HFile did have the entry in it > after you had flushed it. Note that you mentioned the TTL at the CF > level when creating the table, not in your "put" statement, and this > is a vital point in understanding how TTLs work. > > On Wed, Aug 22, 2012 at 1:49 PM, yonghu <yongyong...@gmail.com> wrote: >> I can fully understand normal deletion. But, in my point of view, ttl >> deletion is different than the normal deletion. The insertion of ttl >> data is recorded in hlog. But the ttl deletion is not recorded by >> hlog. So, it failure occurs, should the ttl data be reinserted to data >> or can we discard the certain ttl data? Moreover, ttl deletion is not >> executed at data compaction time. Scanner needs to periodically scan >> each Store file to execute deletion. >> >> regards! >> >> Yong >> >> >> >> On Tue, Aug 21, 2012 at 5:29 PM, jmozah <jmo...@gmail.com> wrote: >>> This helped me >>> http://hadoop-hbase.blogspot.in/2011/12/deletion-in-hbase.html >>> >>> >>> ./Zahoor >>> HBase Musings >>> >>> >>> On 14-Aug-2012, at 6:54 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
