Improve fast deserialization by avoiding field schema retrieval cost

[volauvent]

Improved fast deserialization speed by avoiding current field schema retrieval cost.
Changed to use fields' schema directly instead of registering and then retrieving
them from HashMap.

JMH benchmark results of fast-deserialization time

1. Enum array with 200 elements

        |   Avro 1.4(ns)   |  Avro 1.8(ns)
Before  |   7452           |   13101 
After   |   5374           |   7858 

2. Record array with 200 elements

        |   Avro 1.4(ns)   |   Avro 1.8(ns)
Before  |   23068          |   24519
After   |   17854          |   18549

@gaojieliu @FelixGV @radai-rosenblatt

[gaojieliu]

If I understand correctly, the code change looks good :D

Since the code gen part is quite tricky, Felix and I had a discussion to share a generated seriliazer/de-serializer with the new code gen logic, so that we would be able to see the effect of this change.
So could you share one sample?

[volauvent]

Here are deserializers of EnumArray schema:

Generated deserializer before this PR:
https://gist.github.com/volauvent/76e0f69131bf2ce5b9eeba6a72319d85

Generated deserializer after this PR:
https://gist.github.com/volauvent/13ca4ed55b48e761c8b8e474f0a5da4b

[FelixGV]

Nice results! The generated code LGTM. The code generator is a bit puzzling. I've seen nothing wrong but I'm not confident that I've looked at everything in-depth enough... in any case, if the tests pass and Gaojie thinks it's good, then I guess it's good enough.

BTW, this is off-topic, but do we have a grasp of why 1.8 would perform slower than 1.4?

[gaojieliu]

Sorry, I forgot to follow up, and the generated de-serializer looks good!

[volauvent]

BTW, this is off-topic, but do we have a grasp of why 1.8 would perform slower than 1.4?

The reason why previous fast-avro 1.8 EnumArray deserialization performs much slower than 1.4 is that Avro 1.8 uses Schema and Symbol to construct EnumSymbol while avro 1.4 only uses Symbol.

It leads to fast-deserializer 1.8 suffers 2X cost of retrieving schema from HashMap as bellow

// deserializer in avro 1.8
enumArray2 .add(new org.apache.avro.generic.GenericData.EnumSymbol(
readerSchemaMap.get(4483722390578694240L), 
readerSchemaMap.get(4483722390578694240L).getEnumSymbols().get((decoder.readEnum()))));

// deserializer in avro 1.4
enumArray2 .add(new org.apache.avro.generic.GenericData.EnumSymbol(
readerSchemaMap.get(4483722390578694240L).getEnumSymbols().get((decoder.readEnum()))));

@FelixGV