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From Rene Kochen <rene.koc...@emea.schange.com>
Subject Re: minor compaction and delete expired column-tombstones
Date Mon, 17 Sep 2012 09:01:28 GMT
Oke, thanks!

So a column tombstone will only be removed if all row fragments are
present in the tables being compacted.

I have a row called "Index" which contains columns like "page0",
"page1", "page2", etc. Every several minutes, new columns are created
and old ones deleted. The problem is that I now have an "Index" row in
several SSTables, but the column tombstones are never deleted. And
reading the "Index" row (and all its column tombstones) takes longer
and longer.

If I do a major compaction, all tombstones are deleted and reading the
"index" row takes one millisecond again (and all the garbage-collect
issues because of this).

Is it not advised to use rows with many new column creates/deletes
(because of how minor compactions work)?

Thanks!

Rene

2012/9/17 aaron morton <aaron@thelastpickle.com>:
> Does minor compaction delete expired column-tombstones when the row is
> also present in another table which is
>
> No.
> Compaction is per Column Family.
>
> Tombstones will be expired by Minor Compaction if all fragments of the row
> are contained in the SSTables being compacted.
>
> Cheers
>
> -----------------
> Aaron Morton
> Freelance Developer
> @aaronmorton
> http://www.thelastpickle.com
>
> On 15/09/2012, at 6:32 AM, Rene Kochen <rene.kochen@schange.com> wrote:
>
> Hi all,
>
> Does minor compaction delete expired column-tombstones when the row is
> also present in another table which is not subject to the minor
> compaction?
>
> Example:
>
> Say there are 5 SStables:
>
> - Customers_0 (10 MB)
> - Customers_1 (10 MB)
> - Customers_2 (10 MB)
> - Customers_3 (10 MB)
> - Customers_4 (30 MB)
>
> A minor compaction is triggered which will compact the similar sized
> tables 0 to 3. In these tables is a customer record with key "C1" with
> an expired column tombstone. Customer "C1" is also present in table 4.
> Will the minor compaction delete the column (i.e. will the tombstone
> be present in the newly created table)?
>
> Thanks,
>
> Rene
>
>

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