http://grokbase.com/t/hbase/user/125ya2cxxs/scan-addfamily-vs-familyfilter-equal

http://stackoverflow.com/questions/7256100/scan-with-filter-using-hbase-shell

 

Just to add on.

The java doc clearly says in FamilyFilter that

* If an already known column family is looked for, use {@link

org.apache.hadoop.hbase.client.Get#addFamily(byte[])}

* directly rather than a filter.

So addFamily should be better.

Regards

Ram

-----Original Message-----

From: Anoop Sam John

Sent: Thursday, May 31, 2012 11:49 AM

To: user@hbase.apache.org

Subject: RE: Scan addFamily vs FamilyFilter(EQUAL, ...)

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.ack@gmail.com [saint.ack@gmail.com] on behalf of Stack

[stack@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 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