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Pig >> mail # user >> error with FLATTEN and nested generate


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error with FLATTEN and nested generate
I'm trying to run the following code, ---- I had another piece of code that
looks exactly the same , just var name differences, that one runs fine,
but this one gave errors:

2012-06-20 20:14:38,285 [main] INFO  org.apache.pig.Main - Apache Pig
version 0.10.0-SNAPSHOT (rexported) compiled Jun 20 2012, 16:31:38
2012-06-20 20:14:38,285 [main] INFO  org.apache.pig.Main - Logging error
messages to:
/crypt/yyang_home/work/matching/ML-places-matcher/control_flows/match_suspects/pig_1340248478278.log
2012-06-20 20:14:38,644 [main] INFO
 org.apache.pig.backend.hadoop.executionengine.HExecutionEngine -
Connecting to hadoop file system at: file:///
2012-06-20 20:14:39,148 [main] ERROR org.apache.pig.tools.grunt.Grunt -
ERROR 1200: Pig script failed to parse:
<file a.pig, line 11, column 39> Invalid scalar projection: aa : A column
needs to be projected from a relation for it to be used as a scalar

where I'm I doing wrong?

Thanks a lot
yang

######################################

aa = load 'b' as (x:int , y:int);

b = group aa by x;

c = group b by group ;

-- describe c;
-- c: {group: int,b: {(group: int,aa: {(x: int,y: int)})}}

d = foreach c {
       xx = foreach b generate FLATTEN(aa) as (o:int, p:int);
       generate group , MIN(xx.x);
    };

dump d;