kgyrtkirk commented on a change in pull request #831: HIVE-22238 pkfk
URL: https://github.com/apache/hive/pull/831#discussion_r342535997
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File path: ql/src/java/org/apache/hadoop/hive/ql/stats/StatsUtils.java
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@@ -1961,6 +1961,7 @@ public static void updateStats(Statistics stats, long
newNumRows,
newDV = (long) Math.ceil(ratio * oldDV);
}
cs.setCountDistint(newDV);
+ cs.setFilterColumn();
Review comment:
I'm not sure - I don't think so...actually because we may end up filtering
rows in a join as well - I think it's more accurate to fave this.
I was trying to come up with some query which might be relevant...but they
doesn't really made sense...query requirements:
* we need to have a join condition on the FK - where we would not set it as
a filterColumn
* we need to have a 2. join condition on the same FK
I think queries like the following make not much sense; and the filter on FK
could be movedf to the PK side which has lesser number of rows anyway...so its
kinda useless...
```
select 1 from
torpedos t,
ships s,
something ???,
where
true
-- join#1 condition(x-fk) ; it is required to use t.ship_id
and t.ship_id = ???
-- the pk-fk condition
and t.ship_id = s.id
```
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