Github user wzhfy commented on a diff in the pull request:
https://github.com/apache/spark/pull/18334#discussion_r124456568
--- Diff:
sql/hive/src/test/scala/org/apache/spark/sql/hive/StatisticsSuite.scala ---
@@ -448,6 +433,145 @@ class StatisticsSuite extends
StatisticsCollectionTestBase with TestHiveSingleto
"ALTER TABLE unset_prop_table UNSET TBLPROPERTIES ('prop1')")
}
+ /**
+ * To see if stats exist, we need to check spark's stats properties
instead of catalog
+ * statistics, because hive would change stats in metastore and thus
change catalog statistics.
--- End diff --
Hive updates stats for some formats, e.g. in the test `test statistics of
LogicalRelation converted from Hive serde tables`, hive updates stats for orc
table but not parquet table.
I think it's tricky and fussy to relay on hive's stats, we should rely on
spark's stats. Here I just eliminate hive's influence for checking. As in
`CatalogStatistics` we first fill in hive's stats and then override it using
spark's stats, we can't tell where the stats is from if we check
`CatalogStatistics`.
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