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From "mahesh kumar behera (Jira)" <j...@apache.org>
Subject [jira] [Updated] (HIVE-23903) Support "not-in" for bloom filter
Date Thu, 23 Jul 2020 05:08:00 GMT

     [ https://issues.apache.org/jira/browse/HIVE-23903?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

mahesh kumar behera updated HIVE-23903:
---------------------------------------
    Description: 
In case of anti join, bloom filter can be created on left side also ("IN (keylist right table)").But
the filter should be "not-in" ("NOT IN (keylist right table)") as we want to select the records
from left side which are not present in the right side. But it may cause wrong result as bloom
filter may have false positive and thus simply adding not is not correct, special handling
is required for "NOT IN".

[https://github.com/jmhodges/opposite_of_a_bloom_filter/]

  was:
Currently hive does not support Anti join. The query for anti join is converted to left outer
join and null filter on right side join key is added to get the desired result. This is causing
 # Extra computation — The left outer join projects the redundant columns from right side.
Along with that, filtering is done to remove the redundant rows. This is can be avoided in
case of anti join as anti join will project only the required columns and rows from the left
side table.
 # Extra shuffle — In case of anti join the duplicate records moved to join node can be
avoided from the child node. This can reduce significant amount of data movement if the number
of distinct rows( join keys) is significant.
 # Extra Memory Usage - In case of map based anti join , hash set is sufficient as just the
key is required to check  if the records matches the join condition. In case of left join,
we need the key and the non key columns also and thus a hash table will be required.

For a query like
{code:java}
 select wr_order_number FROM web_returns LEFT JOIN web_sales  ON wr_order_number = ws_order_number
WHERE ws_order_number IS NULL;{code}
The number of distinct ws_order_number in web_sales table in a typical 10TB TPCDS set up is
just 10% of total records. So when we convert this query to anti join, instead of 7 billion
rows, only 600 million rows are moved to join node.

In the current patch, just one conversion is done. The pattern of project->filter->left-join
is converted to project->anti-join. This will take care of sub queries with “not exists”
clause. The queries with “not exists” are converted first to filter + left-join and then
its converted to anti join. The queries with “not in” are not handled in the current patch.

>From execution side, both merge join and map join with vectorized execution  is supported
for anti join.


> Support "not-in" for bloom filter
> ---------------------------------
>
>                 Key: HIVE-23903
>                 URL: https://issues.apache.org/jira/browse/HIVE-23903
>             Project: Hive
>          Issue Type: Bug
>            Reporter: mahesh kumar behera
>            Assignee: mahesh kumar behera
>            Priority: Major
>              Labels: pull-request-available
>
> In case of anti join, bloom filter can be created on left side also ("IN (keylist right
table)").But the filter should be "not-in" ("NOT IN (keylist right table)") as we want to
select the records from left side which are not present in the right side. But it may cause
wrong result as bloom filter may have false positive and thus simply adding not is not correct,
special handling is required for "NOT IN".
> [https://github.com/jmhodges/opposite_of_a_bloom_filter/]



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