andrej-db commented on code in PR #48621:
URL: https://github.com/apache/spark/pull/48621#discussion_r1814515028
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sql/core/src/main/scala/org/apache/spark/sql/jdbc/MsSqlServerDialect.scala:
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@@ -88,11 +88,29 @@ private case class MsSqlServerDialect() extends JdbcDialect
with NoLegacyJDBCErr
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 p: Predicate => inputToCaseWhenSQL(p)
case o => inputToSQL(o)
}
visitBinaryComparison(e.name(), l, r)
- case "CASE_WHEN" =>
visitCaseWhen(expressionsToStringArray(e.children())) + " = 1"
+ case "CASE_WHEN" =>
+ // Since MsSqlServer cannot handle boolean expressions inside
+ // a CASE WHEN, it is necessary to convert those to an IIF
+ // expression that will return 1 or 0 depending on the result.
+ // Example:
+ // In: ... CASE WHEN a = b THEN c = d ...
+ // Out: ... CASE WHEN a = b THEN IIF(c = d, 1, 0) ...
+
+ // grouped turns Array[Expression] to Array[Array[Expression]]
+ // with a len of max 2 (final one will have only one)
+ val stringArray = e.children().grouped(2).flatMap { arr =>
+ arr.dropRight(1).map(inputToSQL) :+
+ (arr.last match {
+ case p: Predicate if p.name() != "ALWAYS_TRUE" && p.name()
!= "ALWAYS_FALSE" =>
Review Comment:
ALWAYS_TRUE gets translated to 1, and that is an int. If wrapped, it will
fail with the same issue we are trying to fix.
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