[jira] [Updated] (CASSANDRA-21075) Optimize UTF8Validator.validate for ASCII prefixed Strings

["Dmitry Konstantinov (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/CASSANDRA-21075?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Dmitry Konstantinov updated CASSANDRA-21075:
--------------------------------------------
    Change Category: Performance
         Complexity: Low Hanging Fruit
      Fix Version/s: 5.x
             Status: Open  (was: Triage Needed)

> Optimize UTF8Validator.validate for ASCII prefixed Strings
> ----------------------------------------------------------
>
>                 Key: CASSANDRA-21075
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-21075
>             Project: Apache Cassandra
>          Issue Type: Improvement
>          Components: CQL/Interpreter
>            Reporter: Dmitry Konstantinov
>            Assignee: Dmitry Konstantinov
>            Priority: Normal
>             Fix For: 5.x
>
>
> In UTF8Validator.validate we can apply the same optimization as Guava and JDK does: they use a plain loop to check if it is ASCII symbol before going into more complicated UTF8 parsing:
>  * [https://github.com/google/guava/blob/master/guava/src/com/google/common/base/Utf8.java#L123]
> {code:java}
> for (int i = off; i < end; i++) {
>     if (bytes[i] < 0) {
>         return isWellFormedSlowPath(bytes, i, end);
>     }
> } {code}
>  * java.lang.StringCoding#decodeUTF8 
> {code:java}
> // ascii-bais, which has a relative impact to the non-ascii-only bytes
> if (COMPACT_STRINGS && !hasNegatives(src, sp, len))
>     return resultCached().with(Arrays.copyOfRange(src, sp, sp + len),
>                                    LATIN1);
> return decodeUTF8_0(src, sp, len, doReplace);
> where:
> public static boolean hasNegatives(byte[] ba, int off, int len) {
>     for (int i = off; i < off + len; i++) {
>         if (ba[i] < 0) {
>             return true;
>         }
>     }
>     return false;
> } {code}
> See also: https://lemire.me/blog/2018/10/16/validating-utf-8-bytes-java-edition/



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