You should read over the
http://wiki.apache.org/hadoop/Hbase/HbaseArchitecture
The data is sorted by row key, then column:label, timestamp
In that order so if you have row key1 all the labels for columnval1 will be
stored together in the same file
We do flush more the one file to disk as data is added so the values are not
always stored together until after a major compaction/merge all store files
together
But what we mean by stored together is all column1 will be stored in one
file and column2 would be stored in a separate set of files so if you only
one data from column1 then you only need to read the data from one set of
files not all the columns for that row key.
also columns for key1 will not be on all the nodes but just one node in the
cluster. The table is split by the key values so keys1-100 would be one
region keys101-200 would be another region all in the same table
We split when the size get to large they split and become two regions and so
on.
So we look up a key we only have to look at one server
Billy
"Ric Wang" <[email protected]> wrote in
message news:[email protected]...
Hi,
Very new to Hadoop and HBase. And sorry about the rudimentary question:
I store my artifacts as rows in an HBase table, and the attributes of each
artifact as labels within one single column family (ex. myFamily). I may
have tens of thousands of labels, and millions and millions of rows. Now
as
the data size grows, some document says that, the values of one family
will
be "stored together". I wonder what that really means.
For example, for a given row key (my.key.123), will HBase guarantee that
ALL
its attributes (ie. the values of ALL the labels in "myFamily") of that
row
key be stored on one physical/grid node? In other words, if I want to find
out ONE contain matching row key "my.key.123" based on its attributes
(column values), at the implementation level, will HBase be
1. traversing all the distributed nodes and interrogating the column
values;
aggregating the results coming from all the nodes; and finally finding out
the matching row key
or
2. doing atomic operations in parallel on each node locally; and finally,
only one node will return the matching row key (if there is a match).
My guess is the that the answer depends on if all attributes (in myFamily)
of a given row are stored on one and only one node.
Hope I didn't make my question very confusing. Very new to column based
database; please help and bare with me.
Thanks!
Ric
