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https://issues.apache.org/jira/browse/HBASE-25576?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Toshihiro Suzuki updated HBASE-25576:
-------------------------------------
Description:
I sometimes face the code where we use a byte array as a key of HashMap
(ConcurrentHashMap) or an element of HashSet, which could cause very confusing
bugs.
The following code is an example where we use a byte array as a key of HashMap:
https://github.com/apache/hbase/blob/326835e8372cc83092e0ec127650438ff153476a/hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/wal/SequenceIdAccounting.java#L94
In Java, we can't use a byte array as a key of HashMap or an element of HashSet
directly. One solution for it is to use TreeMap (ConcurrentSkipListMap) or
TreeSet (ConcurrentSkipListSet) with Bytes.BYTES_COMPARATOR instead of HashMap
and HashSet as follows:
{code}
Map<byte[], String> map1 = new TreeMap<>(Bytes.BYTES_COMPARATOR);
Map<byte[], String> map2 = new ConcurrentSkipListMap<>(Bytes.BYTES_COMPARATOR);
Set<byte[]> set1 = new TreeSet<>(Bytes.BYTES_COMPARATOR);
Set<byte[]> set2 = new ConcurrentSkipListSet<>(Bytes.BYTES_COMPARATOR);
{code}
We should fix the existing ones in this Jira.
was:
I sometimes face the code using HashMap (ConcurrentHashMap) or HashSet when
using byte[] as a key of Map or an element of Set in the HBase code, which
could cause very confusing bugs.
We should use TreeMap (ConcurrentSkipListMap) or TreeSet
(ConcurrentSkipListSet) with Bytes.BYTES_COMPARATOR when using byte[] as a key
of Map or an element of Set as follows:
{code}
Map<byte[], String> map1 = new TreeMap<>(Bytes.BYTES_COMPARATOR);
Map<byte[], String> map2 = new ConcurrentSkipListMap<>(Bytes.BYTES_COMPARATOR);
Set<byte[]> set1 = new TreeSet<>(Bytes.BYTES_COMPARATOR);
Set<byte[]> set2 = new ConcurrentSkipListSet<>(Bytes.BYTES_COMPARATOR);
{code}
We should fix the existing ones in this Jira.
> Should not use a byte array as a key of HashMap or an element of HashSet
> ------------------------------------------------------------------------
>
> Key: HBASE-25576
> URL: https://issues.apache.org/jira/browse/HBASE-25576
> Project: HBase
> Issue Type: Bug
> Reporter: Toshihiro Suzuki
> Assignee: Swaroopa Kadam
> Priority: Major
> Labels: beginner
>
> I sometimes face the code where we use a byte array as a key of HashMap
> (ConcurrentHashMap) or an element of HashSet, which could cause very
> confusing bugs.
> The following code is an example where we use a byte array as a key of
> HashMap:
> https://github.com/apache/hbase/blob/326835e8372cc83092e0ec127650438ff153476a/hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/wal/SequenceIdAccounting.java#L94
> In Java, we can't use a byte array as a key of HashMap or an element of
> HashSet directly. One solution for it is to use TreeMap
> (ConcurrentSkipListMap) or TreeSet (ConcurrentSkipListSet) with
> Bytes.BYTES_COMPARATOR instead of HashMap and HashSet as follows:
> {code}
> Map<byte[], String> map1 = new TreeMap<>(Bytes.BYTES_COMPARATOR);
> Map<byte[], String> map2 = new
> ConcurrentSkipListMap<>(Bytes.BYTES_COMPARATOR);
> Set<byte[]> set1 = new TreeSet<>(Bytes.BYTES_COMPARATOR);
> Set<byte[]> set2 = new ConcurrentSkipListSet<>(Bytes.BYTES_COMPARATOR);
> {code}
> We should fix the existing ones in this Jira.
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