[jira] [Created] (AVRO-4069) Remove Reader String Cache from Generic Datum Reader

["David Mollitor (Jira)" <ji...@apache.org>]

David Mollitor created AVRO-4069:
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             Summary: Remove Reader String Cache from Generic Datum Reader
                 Key: AVRO-4069
                 URL: https://issues.apache.org/jira/browse/AVRO-4069
             Project: Apache Avro
          Issue Type: Improvement
          Components: java
    Affects Versions: 1.12.0
            Reporter: David Mollitor
            Assignee: David Mollitor
             Fix For: 1.13.0


I was doing some profiling, and this "ReaderCache" code lit up:

{code:java}
    public Class getStringClass(final Schema s) {
      final IdentitySchemaKey key = new IdentitySchemaKey(s);
      return this.stringClassCache.computeIfAbsent(key, (IdentitySchemaKey k) -> this.findStringClass.apply(k.schema));
    }
  }

  private final ReaderCache readerCache = new ReaderCache(this::findStringClass);

  protected Class findStringClass(Schema schema) {
    String name = schema.getProp(GenericData.STRING_PROP);
    if (name == null)
      return CharSequence.class;

    switch (GenericData.StringType.valueOf(name)) {
    case String:
      return String.class;
    default:
      return CharSequence.class;
    }
  }
 {code}

The String cache here is simply caching a single value: the class of the {{STRING_PROP}} in the Schema.  Well, this is a lot over overhead for caching a relatively simple mapping. Consider that this must create a new {{IdentitySchemaKey}} object every time it does this lookup and this is a HOT path. It would take less time time, and add less Heap pressure, to perform the simple mapping for each invocation.

Follow on work: the Map in the Schema is synchronized. Maybe the map can be made non-synchronized or the Schema can explicitly cache this value in a non-synchronized way to make this one property load faster.



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