Affects Version/s: 1.15.0
Fix Version/s: None
Component/s: Execution - Flow
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):
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:
|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.