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Date: Tue, 6 Nov 2012 00:34:13 +0000 (UTC)
From: "Christian Spriegel (JIRA)" <jira@apache.org>
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Subject: [jira] [Updated] (CASSANDRA-4917) Optimize tombstone creation for
 ExpiringColumns
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     [ https://issues.apache.org/jira/browse/CASSANDRA-4917?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Christian Spriegel updated CASSANDRA-4917:
------------------------------------------

    Description: 
The goal of this ticket is to reduce the amount of tombstones created from ExpiringColumns.

Currently tombstones will always stay a full gc_grace time, which is not neccessary for ExpiringColumns. We only need to ensure that ExpiringColumn and tombstone together live as long as gc_grace. If the ExpiringColumn's TTL>=gc_grace then we can create an already gcable tombstone and drop that instantly.

My initial proposal was to use the ExpiringColumns creation-timestamp as deletiontime for the tombstone, but Sylvain pointed out that we should not mix local and client timestamps. So I changed it to this:
{code}
public static Column create(ByteBuffer name, ByteBuffer value, long timestamp, int timeToLive, int localExpirationTime, int expireBefore, IColumnSerializer.Flag flag)
{
    if (localExpirationTime >= expireBefore || flag == IColumnSerializer.Flag.PRESERVE_SIZE)
        return new ExpiringColumn(name, value, timestamp, timeToLive, localExpirationTime);
    // the column is now expired, we can safely return a simple tombstone
    return new DeletedColumn(name, localExpirationTime-timeToLive, timestamp);
    // return new DeletedColumn(name, localExpirationTime, timestamp); // old code
}
{code}


This was discussed on the mailinglist: http://cassandra-user-incubator-apache-org.3065146.n2.nabble.com/repair-compaction-and-tombstone-rows-td7583481.html

  was:

The goal of this ticket is to reduce the amount of tombstones created from ExpiringColumns.

Currently tombstones will always stay a full gc_grace time, which is not neccessary for ExpiringColumns. We only need to ensure that ExpiringColumn and tombstone together live as long as gc_grace. If the ExpiringColumn's TTL>=gc_grace then we can create an already gcable tombstone and drop that instantly.

My initial proposal was to use the ExpiringColumns creation-timestamp as deletiontime for the tombstone, but Sylvain pointed out that we should not mix local and client timestamps. So I changed it to this:
{code}
public static Column create(ByteBuffer name, ByteBuffer value, long timestamp, int timeToLive, int localExpirationTime, int expireBefore, IColumnSerializer.Flag flag)
{
    if (localExpirationTime >= expireBefore || flag == IColumnSerializer.Flag.PRESERVE_SIZE)
        return new ExpiringColumn(name, value, timestamp, timeToLive, localExpirationTime);
    // the column is now expired, we can safely return a simple tombstone
    return new DeletedColumn(name, *localExpirationTime-timeToLive*, timestamp);
    // return new DeletedColumn(name, localExpirationTime, timestamp); // old code
}
{code}


This was discussed on the mailinglist: http://cassandra-user-incubator-apache-org.3065146.n2.nabble.com/repair-compaction-and-tombstone-rows-td7583481.html

    
> Optimize tombstone creation for ExpiringColumns
> -----------------------------------------------
>
>                 Key: CASSANDRA-4917
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-4917
>             Project: Cassandra
>          Issue Type: Improvement
>          Components: Core
>            Reporter: Christian Spriegel
>
> The goal of this ticket is to reduce the amount of tombstones created from ExpiringColumns.
> Currently tombstones will always stay a full gc_grace time, which is not neccessary for ExpiringColumns. We only need to ensure that ExpiringColumn and tombstone together live as long as gc_grace. If the ExpiringColumn's TTL>=gc_grace then we can create an already gcable tombstone and drop that instantly.
> My initial proposal was to use the ExpiringColumns creation-timestamp as deletiontime for the tombstone, but Sylvain pointed out that we should not mix local and client timestamps. So I changed it to this:
> {code}
> public static Column create(ByteBuffer name, ByteBuffer value, long timestamp, int timeToLive, int localExpirationTime, int expireBefore, IColumnSerializer.Flag flag)
> {
>     if (localExpirationTime >= expireBefore || flag == IColumnSerializer.Flag.PRESERVE_SIZE)
>         return new ExpiringColumn(name, value, timestamp, timeToLive, localExpirationTime);
>     // the column is now expired, we can safely return a simple tombstone
>     return new DeletedColumn(name, localExpirationTime-timeToLive, timestamp);
>     // return new DeletedColumn(name, localExpirationTime, timestamp); // old code
> }
> {code}
> This was discussed on the mailinglist: http://cassandra-user-incubator-apache-org.3065146.n2.nabble.com/repair-compaction-and-tombstone-rows-td7583481.html

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