Optimization rule FilterAboveForeach is too restrictive and doesn't handle
project * correctly
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Key: PIG-1567
URL: https://issues.apache.org/jira/browse/PIG-1567
Project: Pig
Issue Type: Bug
Reporter: Xuefu Zhang
Fix For: 0.8.0
FilterAboveForeach rule is to optimize the plan by pushing up filter above
previous foreach operator. However, during code review, two major problems were
found:
1. Current implementation assumes that if no projection is found in the filter
condition then all columns from foreach are projected. This issue prevents the
following optimization:
A = LOAD 'file.txt' AS (a(u,v), b, c);
B = FOREACH A GENERATE $0, b;
C = FILTER B BY 8 > 5;
STORE C INTO 'empty';
2. Current implementation doesn't handle * probjection, which means project all
columns. As a result, it wasn't able to optimize the following:
A = LOAD 'file.txt' AS (a(u,v), b, c);
B = FOREACH A GENERATE $0, b;
C = FILTER B BY Identity.class.getName(*) > 5;
STORE C INTO 'empty';
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