davidm-db commented on code in PR #50027:
URL: https://github.com/apache/spark/pull/50027#discussion_r1967153704
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sql/core/src/main/scala/org/apache/spark/sql/scripting/SqlScriptingExecutionNode.scala:
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@@ -599,6 +599,116 @@ class CaseStatementExec(
}
}
+/**
+ * Executable node for SimpleCaseStatement.
+ * @param caseVariableExec Statement with which all conditionExpressions will
be compared to.
+ * @param conditionExpressions Collection of expressions which correspond to
WHEN clauses.
+ * @param conditionalBodies Collection of executable bodies that have a
corresponding condition,
+ * in WHEN branches.
+ * @param elseBody Body that is executed if none of the conditions are met,
i.e. ELSE branch.
+ * @param session Spark session that SQL script is executed within.
+ * @param context SqlScriptingExecutionContext keeps the execution state of
current script.
+ */
+class SimpleCaseStatementExec(
+ caseVariableExec: SingleStatementExec,
+ conditionExpressions: Seq[Expression],
+ conditionalBodies: Seq[CompoundBodyExec],
+ elseBody: Option[CompoundBodyExec],
+ session: SparkSession,
+ context: SqlScriptingExecutionContext) extends NonLeafStatementExec {
+ private object CaseState extends Enumeration {
+ val Condition, Body = Value
+ }
+
+ private var state = CaseState.Condition
+ var bodyExec: Option[CompoundBodyExec] = None
+
+ var conditionBodyTupleIterator: Iterator[(SingleStatementExec,
CompoundBodyExec)] = _
+ private var caseVariableLiteral: Literal = _
+
+ private var isCacheValid = false
+ private def validateCache(): Unit = {
+ if (!isCacheValid) {
+ val values = caseVariableExec.buildDataFrame(session).collect()
+ caseVariableExec.isExecuted = true
+
+ caseVariableLiteral = Literal(values.head.get(0))
+ conditionBodyTupleIterator = createConditionBodyIterator
+ isCacheValid = true
+ }
+ }
+
+ private def cachedCaseVariableLiteral: Literal = {
+ validateCache()
+ caseVariableLiteral
+ }
+
+ private def cachedConditionBodyIterator: Iterator[(SingleStatementExec,
CompoundBodyExec)] = {
+ validateCache()
+ conditionBodyTupleIterator
+ }
+
+ private lazy val treeIterator: Iterator[CompoundStatementExec] =
+ new Iterator[CompoundStatementExec] {
+ override def hasNext: Boolean = state match {
+ case CaseState.Condition => cachedConditionBodyIterator.hasNext ||
elseBody.isDefined
+ case CaseState.Body => bodyExec.exists(_.getTreeIterator.hasNext)
+ }
+
+ override def next(): CompoundStatementExec = state match {
+ case CaseState.Condition =>
+ cachedConditionBodyIterator.nextOption()
+ .map { case (condStmt, body) =>
+ if (evaluateBooleanCondition(session, condStmt)) {
+ bodyExec = Some(body)
+ state = CaseState.Body
+ }
+ condStmt
+ }
+ .orElse(elseBody.map { body => {
+ bodyExec = Some(body)
+ state = CaseState.Body
+ next()
+ }})
+ .get
+ case CaseState.Body => bodyExec.get.getTreeIterator.next()
+ }
+ }
+
+ private def createConditionBodyIterator: Iterator[(SingleStatementExec,
CompoundBodyExec)] =
+ conditionExpressions.zip(conditionalBodies)
+ .iterator
+ .map { case (expr, body) =>
+ val condition = Project(
+ Seq(Alias(EqualTo(cachedCaseVariableLiteral, expr), "condition")()),
+ OneRowRelation()
+ )
+ // We hack the Origin to provide more descriptive error messages. For
example, if
+ // the case variable is 1 and the condition expression it's compared
to is 5, we
+ // will get Origin with text "(1 = 5)".
+ val conditionText =
condition.projectList.head.asInstanceOf[Alias].child.toString
+ val condStmt = new SingleStatementExec(
+ condition,
+ Origin(sqlText = Some(conditionText),
+ startIndex = Some(0),
+ stopIndex = Some(conditionText.length - 1)),
Review Comment:
If it's an easy fix (and it looks like it is) I would definitely go with
this approach (copying the line number to the hacked origin). If not, I think
it's better to keep the line number and then improve the messaging later on as
a follow-up.
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