[
https://issues.apache.org/jira/browse/HBASE-5241?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13221653#comment-13221653
]
Phabricator commented on HBASE-5241:
------------------------------------
aaiyer has commented on the revision "HBASE-5241 [jira] Deletes should not mask
Puts that come after it.".
INLINE COMMENTS
src/main/java/org/apache/hadoop/hbase/regionserver/Store.java:609 It seems
like going for stronger read semantics would disable the space savings we get
by storing the memstoreTS as a (1 byte) Zero value, instead of the actual value.
Perhaps, one way to get similar savings would be to store the actual
memstoreTS in the variable length encoding, after differential encoding.
Here is what I propose.
Keep track of a per-StoreFile startMemstoreTS value, that (approximately)
keeps track of the smallest memstoreTS in the file.
KV's will store the deltas such that KV's-memstoreTS =
StoreFile's-startMemstoreTS + KV-delta.
If the delta is small enough, we will only use 1 or 2 bytes for storing
it. Since we use Bytes.writeVLong: From the java docs:
if n in [-32, 127): encode in one byte with the actual value. Otherwise,
if n in [-20*2^8, 20*2^8): encode in two bytes: byte[0] = n/256 - 52;
byte[1]=n&0xff. Otherwise,
REVISION DETAIL
https://reviews.facebook.net/D1731
> Deletes should not mask Puts that come after it.
> ------------------------------------------------
>
> Key: HBASE-5241
> URL: https://issues.apache.org/jira/browse/HBASE-5241
> Project: HBase
> Issue Type: Improvement
> Reporter: Amitanand Aiyer
> Assignee: Amitanand Aiyer
> Attachments: HBASE-5241.D1731.1.patch, HBASE-5241.D1731.2.patch,
> HBASE-5241.D1731.3.patch
>
>
> Suppose that we have a delete row, and then followed by the put. The delete
> row
> can mask the put, unless there was a major compaction in between.
> Now that we are flushing the memstoreTS to disk, along with the KVs, we
> should be able
> to differentiate whether or not the Put happened after the Delete and offer
> better
> delete semantics.
> Couldn't find a pre-existing JIRA that already discusses this, so creating
> one.
> Seems related to https://issues.apache.org/jira/browse/HBASE-2406, but is not
> quite the same.
--
This message is automatically generated by JIRA.
If you think it was sent incorrectly, please contact your JIRA administrators:
https://issues.apache.org/jira/secure/ContactAdministrators!default.jspa
For more information on JIRA, see: http://www.atlassian.com/software/jira
