Ryan Blue created PIG-4940:
------------------------------
Summary: Predicate push-down filtering unary expressions can be
pushed.
Key: PIG-4940
URL: https://issues.apache.org/jira/browse/PIG-4940
Project: Pig
Issue Type: Bug
Reporter: Ryan Blue
While testing predicate push-down, I ran into the following error:
{code:title=Pig Exception}
ERROR 0: Unsupported conversion of LogicalExpression to Expression: Map
at
org.apache.pig.newplan.FilterExtractor.getExpression(FilterExtractor.java:389)
at
org.apache.pig.newplan.FilterExtractor.getExpression(FilterExtractor.java:401)
at
org.apache.pig.newplan.FilterExtractor.getExpression(FilterExtractor.java:378)
at
org.apache.pig.newplan.FilterExtractor.getExpression(FilterExtractor.java:401)
at
org.apache.pig.newplan.FilterExtractor.getExpression(FilterExtractor.java:380)
at
org.apache.pig.newplan.FilterExtractor.visit(FilterExtractor.java:109)
at
org.apache.pig.newplan.PredicatePushDownFilterExtractor.visit(PredicatePushDownFilterExtractor.java:70)
at
org.apache.pig.newplan.logical.rules.PredicatePushdownOptimizer$PredicatePushDownTransformer.transform(PredicatePushdownOptimizer.java:146)
at
org.apache.pig.newplan.optimizer.PlanOptimizer.optimize(PlanOptimizer.java:110)
... 19 more
{code}
The problem is that the code is trying to push a map access operation, that
isn't supported. The cause appears to be the logic in
{{checkPushDown(UnaryExpression)}} that separates expressions that can be
pushed from expressions that must be run by Pig. This function assumes that any
expression under {{IsNullExpression}} or {{NotExpression}} can be pushed and
adds the unary node's child expression to the pushdown expression without
calling {{checkPushDown}} on it.
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