[Engine-devel] Guid improvements

[Allon Mureinik]

Hi all,

I just merged a couple of improvements to the [N]Guid class [1] to improve it's performance both CPU-wise and memory-wise, based on a set of benchmarks presented by Liran.

What this patchset achieves:
1. Clean up the code, so it's easier to understand and use
2. Eliminate the inflation in the memory foot print caused by the getValue() method
3. Eliminate all the heavy calls to UUID.fromString when creating a new/empty Guid instance as a default value
4. Note that the cleanups proposed in (1) will have minor performance benefits (e.g., eliminating useless conditional statements), but I doubt this would be anything to write home about.

>From a developer's perspective, here's what changed:
1. No more NGuid, just Guid. Both static methods to create a Guid from String still exist, and are named createGuidFromString and createGuidFromStringDefaultEmpty.
2. [N]Guid.getValue() was removed, it's no longer needed after (1) was implemented
3. The Guid() constructor was made private, as it forced a redundant call to UUID.fromString(String). If you need an empty Guid instance, just use Guid.Empty
4. The Guid.EMPTY_GUID_VALUE string constant was removed, as it was used for redundant calls to UUID.fromString. If you really, REALLY, need it, just call Guid.Empty.getValue() for a UUID or Guid.Empty.toString() for a String.
5. All sorts of ways to transform Strings to Guids were removed. If you have a literal you trust, just use new Guid(String). If you suspect it may be null, use Guid.createGuidFromString[DefaultEmpty]
6. NewGuid is now called newGuid. We're in Java, not C# :-)


Many thanks to everyone who reviewed this patchset.
You guys rock!


Regards,
Allon


[1] http://gerrit.ovirt.org/#/q/project:ovirt-engine+branch:master+topic:guid-cleanup,n,z