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From "Chen Luo (JIRA)" <j...@apache.org>
Subject [jira] [Created] (ASTERIXDB-2128) Bloom Filter for LSMBTree is totally useless
Date Fri, 06 Oct 2017 23:23:02 GMT
Chen Luo created ASTERIXDB-2128:
-----------------------------------

             Summary: Bloom Filter for LSMBTree is totally useless
                 Key: ASTERIXDB-2128
                 URL: https://issues.apache.org/jira/browse/ASTERIXDB-2128
             Project: Apache AsterixDB
          Issue Type: Bug
          Components: IDX - Indexes, STO - Storage
            Reporter: Chen Luo
            Assignee: Chen Luo


We use bloom filters on primary index (as LSMBTree) to skip unnecessary pk lookups on some
disk components. The idea is that if the bloom filter reports false on some pk, we totally
skip searching that disk component.

However, in our current complicated BTree/LSMBTree software stack, the bloom filter is completely
useless (in terms of saving I/Os). Take a look at LSMBTreePointSearchCursor. At line 74, we
first call btreeAccessors[i].search(rangeCursors[i], predicate), and then call BloomFilterAwareBTreePointSearchCursor.hasNext()
which performs bloom filter check. However, the call sequence is wrong. Actually, btreeAccessors[i].search
has already searched the primary key against the BTree, from the root down to the leaf, rending
bloom filter completely useless in this case.




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