[GitHub] [spark] dongjoon-hyun commented on a diff in pull request #39660: [SPARK-42128][SQL] Support TOP (N) for MS SQL Server dialect as an alternative to Limit pushdown

[GitBox <gi...@apache.org>]

dongjoon-hyun commented on code in PR #39660:
URL: https://github.com/apache/spark/pull/39660#discussion_r1082103024


##########
sql/core/src/main/scala/org/apache/spark/sql/jdbc/MsSqlServerDialect.scala:
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@@ -167,10 +167,15 @@ private object MsSqlServerDialect extends JdbcDialect {
     throw QueryExecutionErrors.commentOnTableUnsupportedError()
   }
 
+  // SQL Server does not support, it uses `getTopExpression` instead.
   override def getLimitClause(limit: Integer): String = {
     ""
   }
 
+  override def getTopExpression(limit: Integer): String = {
+    if (limit > 0) s"TOP ($limit)" else ""

Review Comment:
   Just curious, MsSQL syntax doesn't allow `TOP 0`?



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