Building on this, you could do something like the following to make it
more random:
if (numRecordsWritten < NUM_RECORDS_DESIRED) {
int n = generateARandomNumberBetween1and100();
if (n == 100) {
context.write(key, value);
}
}
The above would somewhat randomly output 1 record out of every 100, up
to a specified maximum amount desired, and discard all the rest.
HTH,
DR
On 06/27/2011 03:28 PM, Niels Basjes wrote:
The only solution I can think of is by creating a counter in Hadoop
that is incremented each time a mapper lets a record through.
As soon as the value reaches a preselected value the mappers simply
discard the additional input they receive.
Note that this will not at all be random.... yet it's the best I can
come up with right now.
HTH
On Mon, Jun 27, 2011 at 09:11, Jeff Zhang<zjf...@gmail.com> wrote:
Hi all,
I'd like to select random N records from a large amount of data using
hadoop, just wonder how can I archive this ? Currently my idea is that let
each mapper task select N / mapper_number records. Does anyone has such
experience ?
--
Best Regards
Jeff Zhang
