Allow casting relations to scalars
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Key: PIG-1434
URL: https://issues.apache.org/jira/browse/PIG-1434
Project: Pig
Issue Type: Improvement
Reporter: Olga Natkovich
Fix For: 0.8.0
This jira is to implement a simplified version of the functionality described
in https://issues.apache.org/jira/browse/PIG-801.
The proposal is to allow casting relations to scalar types in foreach.
Example:
A = load 'data' as (x, y, z);
B = group A all;
C = foreach B generate COUNT(A);
.....
X = ....
Y = foreach X generate $1/(long) C;
Couple of additional comments:
(1) You can only cast relations including a single value or an error will be
reported
(2) Name resolution is needed since relation X might have field named C in
which case that field takes precedence.
(3) Y will look for C closest to it.
Implementation thoughts:
The idea is to store C into a file and then convert it into scalar via a UDF. I
believe we already have a UDF that Ben Reed contributed for this purpose. Most
of the work would be to update the logical plan to
(1) Store C
(2) convert the cast to the UDF
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