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From "Andy Tolbert (JIRA)" <j...@apache.org>
Subject [jira] [Created] (CASSANDRA-11068) Entire row is compacted away if remaining cells are tombstones expiring after gc_grace_seconds
Date Mon, 25 Jan 2016 19:09:39 GMT
Andy Tolbert created CASSANDRA-11068:
----------------------------------------

             Summary: Entire row is compacted away if remaining cells are tombstones expiring
after gc_grace_seconds
                 Key: CASSANDRA-11068
                 URL: https://issues.apache.org/jira/browse/CASSANDRA-11068
             Project: Cassandra
          Issue Type: Bug
            Reporter: Andy Tolbert


Assuming the following schema:

{code}
CREATE TABLE simple.data (
    k text PRIMARY KEY,
    v int
) WITH gc_grace_seconds = 300;
{code}

And the following queries:

{code}
insert into simple.data (k, v) values ('blah', 1);
delete reading from simple.data where k='blah';
{code}

Performing a {{select *}} from this table will return 1 row with a null value:

{code}
cqlsh> select * from simple.data;

         k | v
-----------+---------
      blah |    null
{code}

Prior the 3.0, if I were to do a flush, the sstable representation of this table would include
an empty cell and a tombstone:

{code}
[
{"key": "blah",
 "cells": [["","",1453747038457027],
           ["v",1453747112,1453747112383096,"d"]]}
]
{code}

As my gc_grace_seconds value is 300, if I wait 5 minutes and perform a compaction, the new
sstable would omit the tombstone, but the empty cell would still be present:

{code}
[
{"key": "blah",
 "cells": [["","",1453747038457027]]}
]
{code}

Performing the {{select *}} query would still yield the same result because of this.

However, in 3.2.1 this does not seem to be the behavior, after deleting the 'v' cell, performing
a flush and then waiting 5 minutes and doing a compact, what ends up happening is that the
sstable completely disappears (presumably because there is no remaining data) and the select
query emits 0 rows:

{code}
cqlsh> select * from simple.data;

         k | v
-----------+---------

(0 rows)
{code}

I'm unsure if this is by design or a bug, but it does represent a change between C* versions.

I have not tried this for a table with clustering columns yet, but I assume that the behavior
will be the same.



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