cloud-fan commented on code in PR #48621:
URL: https://github.com/apache/spark/pull/48621#discussion_r1848306730
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sql/core/src/main/scala/org/apache/spark/sql/jdbc/MsSqlServerDialect.scala:
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@@ -87,13 +87,28 @@ private case class MsSqlServerDialect() extends JdbcDialect
with NoLegacyJDBCErr
expr match {
case e: Predicate => e.name() match {
case "=" | "<>" | "<=>" | "<" | "<=" | ">" | ">=" =>
- val Array(l, r) = e.children().map {
- case p: Predicate => s"CASE WHEN ${inputToSQL(p)} THEN 1 ELSE 0
END"
- case o => inputToSQL(o)
- }
+ val Array(l, r) = e.children().map(inputToSQL)
visitBinaryComparison(e.name(), l, r)
- case "CASE_WHEN" =>
visitCaseWhen(expressionsToStringArray(e.children())) + " = 1"
- case _ => super.build(expr)
+ case "CASE_WHEN" =>
+ // Since MsSqlServer cannot handle boolean expressions inside
+ // a CASE WHEN, it is necessary to convert those to another
+ // CASE WHEN expression that will return 1 or 0 depending on
+ // the result.
+ // Example:
+ // In: ... CASE WHEN a = b THEN c = d ... END
+ // Out: ... CASE WHEN a = b THEN CASE WHEN c = d THEN 1 ELSE 0 END
... END = 1
+ val stringArray = e.children().grouped(2).flatMap {
+ case Array(whenExpression, thenExpression) =>
+ Array(super.build(whenExpression), inputToSQL(thenExpression))
+ case Array(elseExpression) =>
+ Array(inputToSQL(elseExpression))
+ }.toArray
+
+ visitCaseWhen(stringArray) + " = 1"
+ // MsSqlServerDialect translates boolean literals to 1/0, no need to
rewrite them.
+ case "ALWAYS_TRUE" | "ALWAYS_FALSE" =>
+ super.build(expr)
+ case _ => predicateToIntSQL(e)
Review Comment:
```suggestion
case _ => predicateToIntSQL(super.build(e))
```
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