Github user wzhfy commented on a diff in the pull request:
https://github.com/apache/spark/pull/15090#discussion_r79441079
--- 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 --
I think I may know what @hvanhovell meant. The standard deviation is the
parameter we pass to HyperLogLogPlusPlus, so the code may look like this:
```
// ndv is an approximate value, so we make sure we have the value,
and it should be
// within 3*SD's of the given rsd.
assert(colStats.ndv.get >= 0)
val rsd = spark.sessionState.conf.ndvMaxError
val error = math.abs((colStats.ndv.get /
expectedColStats.ndv.get.toDouble) - 1.0d)
assert(error <= rsd * 3.0d, "Error should be within 3 std. errors.")
```
What do you think?
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