Java isset space optimization
-----------------------------
Key: THRIFT-1469
URL: https://issues.apache.org/jira/browse/THRIFT-1469
Project: Thrift
Issue Type: Improvement
Components: Java - Compiler
Affects Versions: 0.8
Reporter: Brian Bloniarz
Priority: Minor
Attached is a small patch and unit tests for Java to optimize the heapspace
footprint of (for example):
struct OptIntPair {
1: i32 a
2: i32 b
}
Each instance will have an __isset_bit_vector which points to a BitSet,
which points to a long[], adding around 50 bytes of overhead to this object.
The patch changes this by storing a raw byte and doing direct bitfield
operations, like:
byte __isset_bitfield;
public void unsetB() {
__isset_bitfield = EncodingUtils.clearBit(__isset_bitfield, __B_ISSET_ID);
}
A little nasty, but a big space win: on my machine, this brings down the total
size of an OptIntPair from 85 bytes to 25 bytes. A BitSet gets used as a
fallback
when more than 64 __isset entries are needed.
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