Github user wzhfy commented on a diff in the pull request:
https://github.com/apache/spark/pull/15090#discussion_r79331568
--- Diff:
sql/core/src/test/scala/org/apache/spark/sql/StatisticsSuite.scala ---
@@ -101,4 +101,47 @@ class StatisticsSuite extends QueryTest with
SharedSQLContext {
checkTableStats(tableName, expectedRowCount = Some(2))
}
}
+
+ test("test column-level statistics for data source table created in
InMemoryCatalog") {
+ def checkColStats(colStats: BasicColStats, expectedColStats:
BasicColStats): Unit = {
+ assert(colStats.dataType == expectedColStats.dataType)
+ assert(colStats.numNulls == expectedColStats.numNulls)
+ assert(colStats.max == expectedColStats.max)
+ assert(colStats.min == expectedColStats.min)
+ if (expectedColStats.ndv.isDefined) {
+ // ndv is an approximate value, so we just make sure we have the
value
+ assert(colStats.ndv.get >= 0)
--- End diff --
What if the number of values is equal to ndv (e.g. primary key)? Can we
expect the estimated mdv from HyperLogLogPlusPlus is always less than the
accurate mdv?
Besides, ndv can be equal to zero.
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