[AVRO-4069] Remove Reader String Cache from Generic Datum Reader

• Type: Improvement
• Status: Open
• Priority: Minor
• Resolution: Unresolved
• Affects Version/s: 1.12.0
• Fix Version/s: 1.13.0
• Component/s: java
• Labels: pull-request-available
• Assignee: David Mollitor
• Reporter: David Mollitor
• Created: 01/Oct/24 03:40
• Updated: 09/Oct/24 10:53

Description

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

    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;
    }
  }
 

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.

Issue Links

• links to: GitHub Pull Request #3194