Travis Woodruff created PIG-4018:
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Summary: Schema validation fails with UNION ONSCHEMA
Key: PIG-4018
URL: https://issues.apache.org/jira/browse/PIG-4018
Project: Pig
Issue Type: Bug
Reporter: Travis Woodruff
Assignee: Travis Woodruff
When relations with differing schemas are unioned (using UNION ONSCHEMA),
schema validation can fail with this exception:
{{org.apache.pig.impl.plan.PlanValidationException: Logical plan invalid state:
invalid uid -1 in schema}}
This worked before the fix for PIG-3492.
The merged schema (from {{LOUnion.getSchema()}}) does not contain uids for
columns not in the schema of the first input (uids are set to -1). This is
because only the first input's schema is used for looking up "cached" uids.
Normally, this isn't a problem because {{UnionOnSchemaSetter}} comes along and
fixes the missing fields.
However, when {{ImplicitSplitInsertVisitor}} is active, it is called before
{{UnionOnSchemaSetter}}. {{ImplicitSplitInsertVisitor}} calls
{{schemaResetter.visit()}}, which throws the validation exception because
{{UnionOnSchemaSetter}} has not had a chance to create the missing fields (and
this uids are still -1 for these fields).
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