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From lars hofhansl <la...@apache.org>
Subject Re: Tables gets Major Compacted even if they haven't changed
Date Tue, 10 Sep 2013 05:41:42 GMT
Interesting. I guess we could add a check to avoid major compactions if (1) no TTL is set or
we can show that all data is newer and (2) there's only one file (3) and there are no delete
markers. All of these can be cheaply checked with some HFile metadata (we might have all data
needed already).

That would take care of both of your scenarios.

-- Lars
From: Premal Shah <premal.j.shah@gmail.com>
To: user <user@hbase.apache.org> 
Sent: Monday, September 9, 2013 9:02 PM
Subject: Tables gets Major Compacted even if they haven't changed

We have a bunch on tables in our HBase cluster. We have a script which
makes sure all of them get Major Compacted once every 2 days. There are 2
things I'm observing

1) Table X has not updated in a month. We have not inserted, updated or
deleted data. However, it still major compacts every 2 days. All the
regions in this table have only 1 store file.

2) Table Y has a few regions where the rowkey is essentially a timestamp.
So, we only write to 1 region at a time. Over time, the region splits, and
then we write the one of the split regions. Now, whenever we major compact
the table, all regions get major compacted. Only 1 region has more than 1
store file, every other region has exactly once.

Is there a way to avoid compaction of regions that have not changed?

We are using HBase 0.94.11

Premal Shah.

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