spark技术分享UnresolvedGenerator Expression
UnresolvedGenerator is a Generator that represents an unresolved generator in a logical query plan.
UnresolvedGenerator is created exclusively when AstBuilder is requested to withGenerate (as part of Generate logical operator) for SQL’s LATERAL VIEW (in SELECT or FROM clauses).
UnresolvedGenerator can never be resolved (and is replaced at analysis phase).
Given UnresolvedGenerator can never be resolved it should not come as a surprise that it cannot be evaluated either (i.e. produce a value given an internal row). When requested to evaluate, UnresolvedGenerator simply reports a UnsupportedOperationException.
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UnresolvedGenerator is similar to UnresolvedFunction and differs mostly by the type (to make Spark development with Scala easier?)
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Creating UnresolvedGenerator Instance
UnresolvedGenerator takes the following when created:
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Child expressions
