spark技术分享Exists — Correlated Predicate Subquery Expression
Exists is a SubqueryExpression and a predicate expression (i.e. the result data type is always boolean).
Exists is created when:
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ResolveSubqueryis requested to resolveSubQueries -
PullupCorrelatedPredicatesis requested to rewriteSubQueries -
AstBuilderis requested to visitExists (in SQL statements)
Exists cannot be evaluated, i.e. produce a value given an internal row.
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Cannot evaluate expression: [this] |
Exists is never nullable.
Exists uses the following text representation:
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exists#[exprId] [conditionString] |
When requested for a canonicalized version, Exists creates a new instance with…FIXME
Creating Exists Instance
Exists takes the following when created:
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Subquery logical plan
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Child expressions
