Hi,
As per my understanding of the Scan code in your scenario where you want
to go with scanning of some CFs ( not all) You go with Scan#addFamily.
The FamilyFilter also doing the same thing. But there is a difference in the
performance.
When one specify the CFs in the scan, the scanner will be created for only
those many Stores. For the other CFs, there wont be any scanners and so those
stores are not scanned. ( The HFile data is not fetched )
Instead when one use the FamilyFilter and not specify any specific columns
(using Scan#addFamily) all the stores will get scanned and data will get
fetched from HFiles. Later these KVs corresponding to which you needed (as per
your FamilyFilter) only will get included in the Result and others just
avoided. So there will be performance difference I feel.. Correct me if I am
wrong pls...
@Stack
>One thing I ran into when using the Scan.addFamily / Scan.addColumn is that
>those two methods overwrite each other.
In the Scan#addColumn javadoc it is clearly telling about this overwrites...
So this seems intentionally done correct?
-Anoop-
________________________________________
From: saint....@gmail.com [saint....@gmail.com] on behalf of Stack
[st...@duboce.net]
Sent: Wednesday, May 30, 2012 11:13 PM
To: user@hbase.apache.org
Subject: Re: Scan addFamily vs FamilyFilter(EQUAL, ...)
On Wed, May 30, 2012 at 9:59 AM, Kevin <kevin.macksa...@gmail.com> wrote:
> I am curious and trying to learn which method is best when wanting to limit
> a scan to a particular column or column family. The Scan class carries a
> Filter instance and a TreeMap of the family map and I am unsure how they
> get carried through to the server-side functionality. In terms of
> performance is there any difference between doing Scan.addFamily(x) and
> Scan.setFilter(new FamilyFilter(CompareFilter.CompareOp.EQUAL, x)?
>
There is probably not noticeable difference in performance but
Scan#addFamily is the more natural way of expressing column family
scoping.
St.Ack
