spark技术分享UnresolvedWindowExpression Unevaluable Expression — WindowExpression With Unresolved Window Specification Reference
UnresolvedWindowExpression is an unevaluable expression that represents…FIXME
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An unevaluable expression cannot be evaluated to produce a value (neither in interpreted nor code-generated expression evaluations) and has to be resolved (replaced) to some other expressions or logical operators at analysis or optimization phases or they fail analysis. |
UnresolvedWindowExpression is created when:
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UnresolvedWindowExpression is created to represent a child expression and WindowSpecReference (with an identifier for the window reference) when AstBuilder parses a function evaluated in a windowed context with a WindowSpecReference.
UnresolvedWindowExpression is resolved to a WindowExpression when Analyzer resolves UnresolvedWindowExpressions.
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import spark.sessionState.sqlParser scala> sqlParser.parseExpression("foo() OVER windowSpecRef") res1: org.apache.spark.sql.catalyst.expressions.Expression = unresolvedwindowexpression('foo(), WindowSpecReference(windowSpecRef)) |
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