Persistent map file using custom marshaller is significantly larger than a using built-in one

[edudar]

I created two maps. One is ChronicleMap<IntValue, Boolean> and another one is ChronicleMap<IntValue, CustomData>. There's also a custom marshaller for CustomData that writes 0 bytes effectively creating a set from a map. That is confirmed in preMapConstruction() when averageValueSize is calculated and it is 0.0. After that, I initialize both maps with 2M, 20M, 200M, and 2B entries on MacOS 10.14. Here's what file sizes look like:

.	2M	20M	200M	2B
Boolean	35.7MB	325.1MB	4.05GB	36.08GB
CustomData	43.3MB	397.9MB	4.76GB	43.18GB

So even when the custom object and its marshaller supposed to take less space, their map file is 20% larger.

Another experiment was with <IntValue, Integer> and <IntValue, Byte> maps. There's no built-in marshaller for Byte, so I created one based on IntegerMarshaller just swapping Integer with Byte and setting the size to 1L instead of 4L.

.	2M
Integer	41.9MB
Byte	45.6MB

That just does not make sense.

[JerryShea]

@edudar is this still a relevant question for you?

[edudar]

I moved away from where I needed ChronicleMap about 2 years ago, so it's not relevant to me personally, but it might be in general.