The flatten will return the same schema as before (in 'first') : so
unless you are modifying the fields or the order in which they are
generated (which I dont think you are in view of your comment that it
should work with and without this), you can simply go with :
-- Or whatever works for you.
%define PARALLELISM '10'
sessions = DISTINCT sessions PARALLEL $PARALLELISM;
OR
sessions = GROUP sessions BY sid PARALLEL $PARALLELISM;
sessions = FOREACH sessions { first = LIMIT sessions 1; GENERATE
FLATTEN(first);};
The schema at the end would be exactly same as start of the code snippet
for 'sessions'.
Regards,
Mridul
On Tuesday 13 July 2010 01:01 PM, Vincent Barat wrote:
Le 12/07/10 16:56, Mridul Muralidharan a écrit :
I am not sure what you mean here exactly.
Will a sid row have multiple (different) values for the other
fields ?
Yes.
But if you want to pick any one row for a given sid, then I think
what you have below might be good enough (you can omit the last
line though).
OK. Thanks. The last line is used to retrieve the exact same data
structure and naming as the original table. This way, I can
optionally perform this treatment without modifying my code. If you
know a better way...
Cheers,
Regards,
Mridul
On Monday 12 July 2010 06:53 PM, Vincent Barat wrote:
Hello everybody,
I have a simple table containing sessions. Each sessions has an
unique key (the sid, which is actually a uuid).
But a session can be present several times in my input table.
I want to ensure that I only have 1 record for each sid (because I
perform subsequent JOIN based on this sid).
Currently I use the following script, but I wonder if there is
something more efficient:
sessions = GROUP sessions BY sid;
sessions = FOREACH sessions { first = LIMIT sessions 1; GENERATE
FLATTEN(first);};
sessions = FOREACH sessions GENERATE sid, .. and all the fields I
have in the session table...
Do you see any optimization I can do, especially on the FLATTEN /
GENERATE part ?
Thank you very much for your help.
