Github user HyukjinKwon commented on a diff in the pull request:

    https://github.com/apache/spark/pull/8391#discussion_r39345352
  
    --- Diff: 
sql/core/src/main/scala/org/apache/spark/sql/execution/datasources/jdbc/JDBCRDD.scala
 ---
    @@ -275,6 +275,10 @@ private[sql] class JDBCRDD(
        */
       private def compileFilter(f: Filter): String = f match {
         case EqualTo(attr, value) => s"$attr = ${compileValue(value)}"
    +    // Since the null-safe equality operator is not a standard SQL 
operator,
    +    // This was written as using is-null and normal equality.
    +    case EqualNullSafe(attr, value) =>
    +      s"($attr = ${compileValue(value)} OR ($attr IS NULL AND 
${compileValue(value)} IS NULL))"
    --- End diff --
    
    Yes.. it looks so. There can be a problem if the query uses the result of  
comparison `<=>`.
    
    Let me correct this as `(NOT ($attr <> ${compileValue(value)} OR $attr IS 
NULL OR ${compileValue(value)} IS NULL) OR ($attr IS NULL AND 
${compileValue(value)} IS NULL))`.
    
    (BTW, I found `<=>` actually a standard but as `IS NOT DISTINCT FROM` from 
SQL1999)



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