[GitHub] [spark] wzhfy commented on a change in pull request #35440: [SPARK-38140][SQL] Desc column stats (min, max) for timestamp type is not consistent with the values due to time zone difference

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

wzhfy commented on a change in pull request #35440:
URL: https://github.com/apache/spark/pull/35440#discussion_r802796394



##########
File path: sql/core/src/test/scala/org/apache/spark/sql/StatisticsCollectionSuite.scala
##########
@@ -470,7 +470,98 @@ class StatisticsCollectionSuite extends StatisticsCollectionTestBase with Shared
     }
   }
 
-  def getStatAttrNames(tableName: String): Set[String] = {
+  private def checkDescTimestampColStatsByZone(
+      tableName: String,
+      timestampColumn: String,
+      expectedMinTimestamp: String,
+      expectedMaxTimestamp: String): Unit = {
+
+    def extractColumnStatsFromDesc(statsName: String, rows: Array[Row]): String = {
+      rows.collect {
+        case r: Row if r.getString(0) == statsName =>
+          r.getString(1)
+      }.head
+    }
+
+    val descTsCol = sql(s"DESC FORMATTED $tableName $timestampColumn").collect()
+    assert(extractColumnStatsFromDesc("min", descTsCol) == expectedMinTimestamp)
+    assert(extractColumnStatsFromDesc("max", descTsCol) == expectedMaxTimestamp)
+  }
+
+  test("describe column stats (min, max) for timestamp column: desc results should be consistent " +
+    "with the written value if writing and desc happen in the same time zone") {
+
+    val original = TimeZone.getDefault
+    try {
+      Seq("UTC", "PST", "Asia/Hong_Kong").foreach { timeZoneId =>
+        val table = "insert_desc_same_time_zone"
+        val tsCol = "timestamp_typed_col"
+        withTable(table) {
+
+          TimeZone.setDefault(DateTimeUtils.getTimeZone(timeZoneId))
+
+          val minTimestamp = "make_timestamp(2022, 1, 1, 0, 0, 1.123456)"
+          val maxTimestamp = "make_timestamp(2022, 1, 3, 0, 0, 2.987654)"
+          sql(s"CREATE TABLE $table ($tsCol Timestamp) USING parquet")
+          sql(s"INSERT INTO $table VALUES $minTimestamp, $maxTimestamp")
+          sql(s"ANALYZE TABLE $table COMPUTE STATISTICS FOR ALL COLUMNS")
+
+          checkDescTimestampColStatsByZone(
+            tableName = table,
+            timestampColumn = tsCol,
+            expectedMinTimestamp = "2022-01-01 00:00:01.123456",
+            expectedMaxTimestamp = "2022-01-03 00:00:02.987654")
+        }
+      }
+    } finally {
+      TimeZone.setDefault(original)
+    }
+  }
+
+  test("describe column stats (min, max) for timestamp column: desc should show different " +
+    "results if writing in UTC and desc in other time zones") {
+
+    val table = "insert_desc_diff_time_zones"
+    val tsCol = "timestamp_typed_col"
+
+    val original = TimeZone.getDefault

Review comment:
       Thanks! Didn't know we have this util method. Updated.




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