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WindowSpecDefinition Unevaluable Expression

WindowSpecDefinition is an unevaluable expression.

WindowSpecDefinition is <> when:

import org.apache.spark.sql.expressions.Window
val byValueDesc = Window.partitionBy("value").orderBy($"value".desc)

val q = table.withColumn("count over window", count("*") over byValueDesc)

import org.apache.spark.sql.catalyst.expressions.WindowExpression
val windowExpr = q.queryExecution
  .logical
  .expressions(1)
  .children(0)
  .asInstanceOf[WindowExpression]

scala> windowExpr.windowSpec
res0: org.apache.spark.sql.catalyst.expressions.WindowSpecDefinition = windowspecdefinition('value, 'value DESC NULLS LAST, UnspecifiedFrame)
import org.apache.spark.sql.catalyst.expressions.WindowSpecDefinition

Seq((0, "hello"), (1, "windows"))
  .toDF("id", "token")
  .createOrReplaceTempView("mytable")

val sqlText = """
  SELECT count(*) OVER myWindowSpec
  FROM mytable
  WINDOW
    myWindowSpec AS (
      PARTITION BY token
      ORDER BY id
      RANGE BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW
    )
"""

import spark.sessionState.{analyzer,sqlParser}

scala> val parsedPlan = sqlParser.parsePlan(sqlText)
parsedPlan: org.apache.spark.sql.catalyst.plans.logical.LogicalPlan =
'WithWindowDefinition Map(myWindowSpec -> windowspecdefinition('token, 'id ASC NULLS FIRST, RANGE BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW))
+- 'Project [unresolvedalias(unresolvedwindowexpression('count(1), WindowSpecReference(myWindowSpec)), None)]
   +- 'UnresolvedRelation `mytable`

import org.apache.spark.sql.catalyst.plans.logical.WithWindowDefinition
val myWindowSpec = parsedPlan.asInstanceOf[WithWindowDefinition].windowDefinitions("myWindowSpec")

scala> println(myWindowSpec)
windowspecdefinition('token, 'id ASC NULLS FIRST, RANGE BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW)

scala> println(myWindowSpec.sql)
(PARTITION BY `token` ORDER BY `id` ASC NULLS FIRST RANGE BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW)

scala> sql(sqlText)
res4: org.apache.spark.sql.DataFrame = [count(1) OVER (PARTITION BY token ORDER BY id ASC NULLS FIRST RANGE BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW): bigint]

scala> println(analyzer.execute(sqlParser.parsePlan(sqlText)))
Project [count(1) OVER (PARTITION BY token ORDER BY id ASC NULLS FIRST RANGE BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW)#25L]
+- Project [token#13, id#12, count(1) OVER (PARTITION BY token ORDER BY id ASC NULLS FIRST RANGE BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW)#25L, count(1) OVER (PARTITION BY token ORDER BY id ASC NULLS FIRST RANGE BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW)#25L]
   +- Window [count(1) windowspecdefinition(token#13, id#12 ASC NULLS FIRST, RANGE BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW) AS count(1) OVER (PARTITION BY token ORDER BY id ASC NULLS FIRST RANGE BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW)#25L], [token#13], [id#12 ASC NULLS FIRST]
      +- Project [token#13, id#12]
         +- SubqueryAlias mytable
            +- Project [_1#9 AS id#12, _2#10 AS token#13]
               +- LocalRelation [_1#9, _2#10]

[[properties]] .WindowSpecDefinition's Properties [width="100%",cols="1,2",options="header"] |=== | Name | Description

| [[children]] children | Window <> and <> specifications (for which WindowExpression was created).

| dataType | Unsupported (i.e. reports a UnsupportedOperationException)

| foldable | Disabled (i.e. false)

| nullable | Enabled (i.e. true)

| resolved | Enabled when <> are and the input DataType is valid and the input frameSpecification is a SpecifiedWindowFrame.

| sql a| Contains PARTITION BY with comma-separated elements of <> (if defined) with ORDER BY with comma-separated elements of <> (if defined) followed by <>.

[options="wrap"]

(PARTITION BY token ORDER BY id ASC NULLS FIRST RANGE BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW)

|===

Creating Instance

WindowSpecDefinition takes the following when created:

  • [[partitionSpec]] <> for window partition specification
  • [[orderSpec]] Window order specifications (as SortOrder unary expressions)
  • [[frameSpecification]] Window frame specification (as WindowFrame)

=== [[isValidFrameType]] Validating Data Type Of Window Order-- isValidFrameType Internal Method

[source, scala]

isValidFrameType(ft: DataType): Boolean

isValidFrameType is positive (true) when the data type of the <> and the input ft data type are as follows:

Otherwise, isValidFrameType is negative (false).

NOTE: isValidFrameType is used exclusively when WindowSpecDefinition is requested to <> (with RangeFrame as the <>)

=== [[checkInputDataTypes]] Checking Input Data Types -- checkInputDataTypes Method

[source, scala]

checkInputDataTypes(): TypeCheckResult

checkInputDataTypes is part of the Expression abstraction.

checkInputDataTypes...FIXME


Last update: 2020-10-21