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From: Marc Sturm <mas9161@nyp.org>
To: "user@hbase.apache.org" <user@hbase.apache.org>
Subject: question about composite rowKey and performance difference between
 getScanner() and get(Get[])
Thread-Topic: question about composite rowKey and performance difference
 between getScanner() and get(Get[])
Thread-Index: AdAPN0hcqBpnM4+mStmLFyH+ELyh6w==
Date: Wed, 3 Dec 2014 20:31:20 +0000
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Hi,

I have a many to many relationship that I am trying to model in hbase, and=
 I want to be sure I am not missing anything so please let me know or poin=
t to the right documentation.

Let's say I have an A to B many to many relationship, the query parameter =
takes A unique id and returns all the B uniqueids related to A with their =
properties and values.

The first solution I found is having two tables: one with the rowKey equal=
 to A's unique id, the table column identifiers are equal to B's unique id=
s related to A, the second table has its rowKeys equal to B unique ids and=
 its columns contain the property values. So the query is two steps, it fi=
rst does a get on A to collect all the B uniqueIds and then does a second =
get on the B passing as a parameter an array of B rowkeys. When I run the =
second query, I can get a latency much longer on the first query and then =
good low latency on subsequent queries with same parameter. I believe that=
's a caching issue...

The second solution is having one table with a composite rowkey equal to A=
 uniqueid + B uniqueid, I will then have duplicate B uniqueid rows. But wh=
en I do a scan on the just the first part of the rowKey (A uniqueid) the r=
esponse time and latency is more consistent and better (smaller).

So, my questions are threefold: 1) which way is the best, 2) what is the p=
erformance difference between a scan and a get with multiple rowkeys (I th=
ink scan is faster because the data is not or less "distributed") and 3) h=
ow can we make the get with multiple rowkeys more consistent?

Thank you for your help,
Marc

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