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From David Larsen <dlar...@aislea.com>
Subject Deleted cells surviving compaction
Date Wed, 26 Mar 2014 00:44:53 GMT
My understanding of delete operations is that a delete essentially writes out a tombstone for
the cell.  Cells aren't actually deleted until a major compaction.

I performed the following sequence on a single cell:

1) Put
2) Delete with a timestamp of HConstants.LATEST_TIMESTAMP
3) Major compact table
4) Put
5) Do a regular scan or get... no value returned
6) Do a raw scan, and I see this:

myRowKey                              column=myColumn, timestamp=9223372036854775807, type=DeleteColumn

On one hand, I understand at a simple level why my HConstants.LATEST_TIMESTAMP on the Delete
would create a sort of black hole where no future Put with a "real" timestamp would get in
front of that timestamp.  However, I'm curious why the tombstone appears not to get cleared
out with the major compact.  Am I just misunderstanding expected behavior?

--
version: 0.94.6-cdh4.5.0.
hbase(main):019:0> describe 'myTable'
DESCRIPTION                                                                              
                ENABLED
 {NAME => 'STAG_aiSnap2', FAMILIES => [{NAME => 'C', DATA_BLOCK_ENCODING => 'NONE',
BLOOMFILTER => 'NONE' true
 , REPLICATION_SCOPE => '0', VERSIONS => '1', COMPRESSION => 'SNAPPY', MIN_VERSIONS
=> '0', TTL => '21474
 83647', KEEP_DELETED_CELLS => 'false', BLOCKSIZE => '65536', IN_MEMORY => 'false',
ENCODE_ON_DISK => 'tr
 ue', BLOCKCACHE => 'true'}]}

--
David Larsen
Software Engineer | Aisle A
dlarsen@AisleA.com<mailto:dlarsen@AisleA.com>

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