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From "Santhosh Srinivasan" <...@yahoo-inc.com>
Subject RE: Data types for Map key value pairs
Date Thu, 15 Jan 2009 18:32:57 GMT
You can specify map types as colname: map[] in your load statement.

E.g.: a = load 'mydata' as (x: int, m: map[]);

Note that Pig does not enforce types for the keys and values in the map.
The only constraint is that keys should be basic types (int, long,
float, double, string). Internally, the value types are treated as
bytearray allowing the use of any Pig type as the value type. This
allows you to have any type (int, long, float, double, string, tuple,
bag, map) as the value type.

I hope that answers your question regarding types inside a map in Pig.
Let me know if you have further questions/clarifications.

Thanks,
Santhosh 

-----Original Message-----
From: ANKUR GOEL [mailto:ankur.goel@corp.aol.com] 
Sent: Thursday, January 15, 2009 6:35 AM
To: pig-dev@hadoop.apache.org
Cc: pig-user@hadoop.apache.org
Subject: Data types for Map key value pairs

Hi All,
           I have a custom loader that returns a set of fields after 
reading a log line. One of the fields returned is of type DataType.Map. 
My question is how can I set the data types for this map's (key, value) 
pair. In my script I try to generate a record from k,v of this map and 
get the error

java.io.IOException: Unknown type Unknown
	at
org.apache.pig.backend.hadoop.executionengine.mapReduceLayer.PigMapBase.
map(PigMapBase.java:178)
	at
org.apache.pig.backend.hadoop.executionengine.mapReduceLayer.PigMapOnly$
Map.map(PigMapOnly.java:65)
	at org.apache.hadoop.mapred.MapRunner.run(MapRunner.java:47)
	at org.apache.hadoop.mapred.MapTask.run(MapTask.java:227)
	at
org.apache.hadoop.mapred.TaskTracker$Child.main(TaskTracker.java:2207)


here is my script
raw =  LOAD 'myfile' USING myUdf.MyCustomLoader() ;
filtered = FILTER raw BY (ARG_MAP#'key' is not null);
entry = FOREACH filtered GENERATE A, B, myUdf.MySplit(ARG_MAP#'key', 
'|') as FIELDS; // This returns a map with String (key, value) pairs
// The MySplit UDF line splits the value in the map which is "|" 
separated and puts the splits it into another Map and returns it. Each 
split is keyed by 'field0', 'field1'...'fieldn' where n is the number of

splits.

result = FOREACH entry GENERATE A, B,  FIELDS#'field0' as CLIENT_ID, 
FIELDS#'field1' as CHANNEL_ID, FIELDS#'field2' as OTHER_ID;
// Here another tuple is generated

store results into 'location' using PigStorage();

Any help here is appreciated.

TIA
-Ankur

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