[DRILL-6727] JPPD does not eliminate rows using the bloom filter if a HashJoin is involved

• Type: Improvement
• Status: Closed
• Priority: Critical
• Resolution: Fixed
• Affects Version/s: 1.15.0
• Component/s: Execution - Flow
• Flags: Important
• Assignee: Weijie Tong
• Reporter: Kunal Khatua
• Created: 02/Sep/18 05:40
• Updated: 12/Nov/18 07:51
• Resolved: 12/Nov/18 07:51

Description

When testing a simple join between 2 tables, it appears that the Bloom-filter based predicate pushdown will work only for broadcast joins, but not for hash-based joins.

Since the purpose of the filter is to reduce the number of records being hashed across the fragments, the runtime does not improve.

Join Query (TPCH dataset):

select
l.l_orderkey
, sum(l.l_extendedprice * (1 - l.l_discount)) as revenue
, o.o_orderdate
, o.o_shippriority
from
orders o
, lineitem l
where
l.l_orderkey = o.o_orderkey
and o.o_orderdate = date '1994-08-26'
and MOD(o.o_custkey,10) = 1
group by
l.l_orderkey
, o.o_orderdate
, o.o_shippriority
order by
revenue desc
, o.o_orderdate limit 10;

This generates an output of about 6K rows from the build side, with the expectation of 10M rows being joined from the probe side.

Following are the results of the following query:

Join Mode	Profile	Runtime	Status
BCastJoin w/o JPPD	bcastJoin-default_2477fa68-a31e-3b97-5469-373845c2b763.json	3.148sec	As expected. 600M rows are scanned and probed against the locally available hash table.
BCastJoin w/ JPPD	bcastJoin-JPPD_2477fb99-36cb-9bc2-b7fb-c81a52b256d2.json	3.570sec	04-xx-06 shows a reduction in rows. 600M rows are scanned, but only 10M rows are probed against the locally available hash table.
HashJoin w/o JPPD	hashJoin-default_2477f5e8-fff2-fc83-d251-d8be8f92820b.json	5.861sec	As expected. 600M rows are scanned and probed against the hash table.
HashJoin w/ JPPD	hashJoin-JPPD_2477f6f7-14e0-ca23-d9f7-6b0273c20964.json	8.376sec	03-xx-07 is not seeing a reduction in rows. All 600M rows are scanned and probed against the hash table.

There are a few possibilities of why the RuntimeFilter does not eliminate any rows when a HashJoin is involved.
1. The RuntimeFilter operator does not have a bloom-filter
2. The RuntimeFilter receives the bloom-filter after the scan completes, because the foreman has not finished building and distributing the global bloom-filter
3. The RuntimeFilter receives the bloom-filter during the scan, but does not apply it.

Issue Links

• relates to: DRILL-6385 Support JPPD (Join Predicate Push Down)