cloud-fan commented on code in PR #50112:
URL: https://github.com/apache/spark/pull/50112#discussion_r1979431491
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sql/core/src/main/scala/org/apache/spark/sql/jdbc/MySQLDialect.scala:
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@@ -54,10 +54,31 @@ private case class MySQLDialect() extends JdbcDialect with
SQLConfHelper with No
override def visitExtract(field: String, source: String): String = {
field match {
case "DAY_OF_YEAR" => s"DAYOFYEAR($source)"
- case "YEAR_OF_WEEK" => s"EXTRACT(YEAR FROM $source)"
+ // The second argument of WEEK is mode, which controls the first day
of the week, the range
+ // of return value, config of week 1 (with a Sunday in this year, with
4 or more days this
+ // year, with a Monday in this year).
+ // The mode 3 means the first day of the week is Monday, the range of
return value is 1-53
+ // and week 1 is the first week with 4 or more days this year. In the
other word, mode 3
+ // has the same semantics as ISO week.
+ case "WEEK" => s"WEEK($source, 3)"
+ // MySQL doesn't support extract the ISO year. We use the case
statements shown below to
+ // get it.
+ // CASE
+ // WHEN WEEK(date, 3) = 1 AND MONTH(date) = 12 THEN YEAR(date) + 1
+ // WHEN WEEK(date, 3) >= 52 AND MONTH(date) = 1 THEN YEAR(date) - 1
+ // ELSE YEAR(date)
Review Comment:
This looks fragile, shall we reject such EXTRACT to be pushed down?
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