[
https://issues.apache.org/jira/browse/DRILL-1212?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14078928#comment-14078928
]
Jacques Nadeau commented on DRILL-1212:
---------------------------------------
fixed by 0d6befc or earlier
> Remove extra exchange operator when generate a two phase aggregation plan.
> --------------------------------------------------------------------------
>
> Key: DRILL-1212
> URL: https://issues.apache.org/jira/browse/DRILL-1212
> Project: Apache Drill
> Issue Type: Bug
> Reporter: Jinfeng Ni
>
> We may see an extra hash exchange operator, when optimizer choose a two phase
> aggregation plan, for a query with group by GB_Key order by OB_Key and GB_key
> is same as Ob_key.
> One example of such plan with extra exchange is TPCH Q12:
> select
> l.l_shipmode,
> sum(case
> when o.o_orderpriority = '1-URGENT'
> or o.o_orderpriority = '2-HIGH'
> then 1
> else 0
> end) as high_line_count,
> sum(case
> when o.o_orderpriority <> '1-URGENT'
> and o.o_orderpriority <> '2-HIGH'
> then 1
> else 0
> end) as low_line_count
> from
> cp.`tpch/orders.parquet` o,
> cp.`tpch/lineitem.parquet` l
> where
> o.o_orderkey = l.l_orderkey
> and l.l_shipmode in ('TRUCK', 'REG AIR')
> and l.l_commitdate < l.l_receiptdate
> and l.l_shipdate < l.l_commitdate
> and l.l_receiptdate >= date '1994-01-01'
> and l.l_receiptdate < date '1994-01-01' + interval '1' year
> group by
> l.l_shipmode
> order by
> l.l_shipmode;
> The issue is caused by the rule does not propagate the hash distribution up,
> and hence introduce unnecessary hash exchange.
>
--
This message was sent by Atlassian JIRA
(v6.2#6252)
