@Retention(value=RUNTIME) @Target(value=TYPE) @Documented public @interface WindowFunctionDescription
Modifier and Type | Required Element and Description |
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Description |
description |
Modifier and Type | Optional Element and Description |
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boolean |
impliesOrder
Using in analytical functions to specify that UDF implies an ordering
|
boolean |
pivotResult
A WindowFunc is implemented as
GenericUDAFResolver2 . |
boolean |
rankingFunction
Used in translations process to validate arguments
|
boolean |
supportsWindow
controls whether this function can be applied to a Window.
|
public abstract Description description
public abstract boolean supportsWindow
Ranking function: Rank, Dense_Rank, Percent_Rank and Cume_Dist don't operate on Windows. Why? a window specification implies a row specific range i.e. every row gets its own set of rows to process the UDAF on. For ranking defining a set of rows for every row makes no sense.
All other UDAFs can be computed for a Window.
public abstract boolean pivotResult
GenericUDAFResolver2
. It returns only one value.
If this is true then the function must return a List which is taken to be the column for this function in the Output table returned by the
WindowingTableFunction
. Otherwise the output is assumed to be a single value, the column of the Output will contain the same value
for all the rows.Copyright © 2016 The Apache Software Foundation. All rights reserved.