[
https://issues.apache.org/jira/browse/AVRO-2905?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]
Kyoungha Min updated AVRO-2905:
-------------------------------
Description:
Bug : utf8 hash reset is not correctly done, as a result, returns different
hash when the values are logically equal.
cause commit :
[https://github.com/apache/avro/commit/d5d1cd70e920f45468bf696d3668b496a9adbab3#diff-7001731cdafe4fc24f86e71c7e8a0b61]
[https://github.com/apache/avro/commit/8e345c48e8f9708c27af63754965777314dac85c#diff-7001731cdafe4fc24f86e71c7e8a0b61]
reproduce :
{code:java}
org.apache.avro.util.Utf8 utf8 = new org.apache.avro.util.Utf8();
utf8.set("hello");
System.out.println(utf8.hashCode()); // 99162322
utf8.set("hello");
System.out.println(utf8.hashCode()); // -1538739392
{code}
Suggested fix.
# get rid of `hasHash` field. In my opinion, it leads to more bug-prone by
adding additional variable to take care of. `hash != 0` should be enough to
check the presence of hash. Redundant computation for `0 hash` elements should
be negligible.
# reset `hash = 0` on every mutation call.
# not needed, but I want to see some minor optimization like avoiding memory
access by creating local variable (int hash = 0; .... this.hash = hash).
was:
Bug : utf8 hash reset is not correctly done, as a result, returns different
hash when the values are logically equal.
cause commit :
[https://github.com/apache/avro/commit/d5d1cd70e920f45468bf696d3668b496a9adbab3#diff-7001731cdafe4fc24f86e71c7e8a0b61]
[https://github.com/apache/avro/commit/8e345c48e8f9708c27af63754965777314dac85c#diff-7001731cdafe4fc24f86e71c7e8a0b61]
reproduce :
```
org.apache.avro.util.Utf8 utf8 = new org.apache.avro.util.Utf8();
utf8.set("hello");
System.out.println(utf8.hashCode()); // 99162322
utf8.set("hello");
System.out.println(utf8.hashCode()); // -1538739392
```
Suggested fix.
# get rid of `hasHash` field. In my opinion, it leads to more bug-prone by
adding additional variable to take care of. `hash != 0` should be enough to
check the presence of hash. Redundant computation for `0 hash` elements should
be negligible.
# reset `hash = 0` on every mutation call.
# I want to see some minor optimization like avoiding memory access by
creating local variable (int hash = 0; .... this.hash = hash).
> org.apache.avro.util.Utf8 bug in `hashCode`
> -------------------------------------------
>
> Key: AVRO-2905
> URL: https://issues.apache.org/jira/browse/AVRO-2905
> Project: Apache Avro
> Issue Type: Bug
> Components: java
> Affects Versions: 1.10.0
> Reporter: Kyoungha Min
> Priority: Major
>
> Bug : utf8 hash reset is not correctly done, as a result, returns different
> hash when the values are logically equal.
>
> cause commit :
>
> [https://github.com/apache/avro/commit/d5d1cd70e920f45468bf696d3668b496a9adbab3#diff-7001731cdafe4fc24f86e71c7e8a0b61]
> [https://github.com/apache/avro/commit/8e345c48e8f9708c27af63754965777314dac85c#diff-7001731cdafe4fc24f86e71c7e8a0b61]
>
> reproduce :
> {code:java}
> org.apache.avro.util.Utf8 utf8 = new org.apache.avro.util.Utf8();
> utf8.set("hello");
> System.out.println(utf8.hashCode()); // 99162322
> utf8.set("hello");
> System.out.println(utf8.hashCode()); // -1538739392
> {code}
>
> Suggested fix.
> # get rid of `hasHash` field. In my opinion, it leads to more bug-prone by
> adding additional variable to take care of. `hash != 0` should be enough to
> check the presence of hash. Redundant computation for `0 hash` elements
> should be negligible.
> # reset `hash = 0` on every mutation call.
> # not needed, but I want to see some minor optimization like avoiding memory
> access by creating local variable (int hash = 0; .... this.hash = hash).
>
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