[Fix] Part-2 - LevelDbStore

[cschuchardt88]

Description

This fixes the store's dotnet memory management for GC, a long with adding new feature options, easier Exception catching.

Change Log

• Added LevelDbStoreTests for unit testing DB and Iterator

Type of change

• Optimization (the change is only an optimization)
• Style (the change is only a code style for better maintenance or standard purpose)
• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

How Has This Been Tested?

Unit tests

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules

[shargon]

Suggested change

	FilterPolicy = 10,
	FilterPolicy = Native.leveldb_filterpolicy_create_bloom(15),

?

[cschuchardt88]

No need for extra, 5 bits. Bloom filters should be as small as possible for datasets without that many collisions. 10 is way more than enough. Speed is key...

[shargon]

Suggested change

	? _db.Seek(prefix, new ReadOptions { FillCache = false, })
	: _db.SeekPrev(prefix, new ReadOptions { FillCache = false, });
	? _db.Seek(prefix, ReadOptions.Default)
	: _db.SeekPrev(prefix, ReadOptions.Default);

[cschuchardt88]

This will cause problem, because ReadOptions.Default is static readonly and will use the same instance. So if someone changes ReadOptions.Default parameters will cause problems for us. Thats why I coded it this way.

[cschuchardt88]

ReadOptions.Default isnt the same as new ReadOptions { FillCache = false, }

[shargon]

Suggested change

	if (disposing)
	{
	FreeManagedObjects();
	}
	if (Handle != nint.Zero)
	{
	FreeUnManagedObjects();
	Handle = nint.Zero;
	}
	_disposed = true;
	}
	_disposed = true;
	if (disposing)
	{
	FreeManagedObjects();
	}
	if (Handle != nint.Zero)
	{
	FreeUnManagedObjects();
	Handle = nint.Zero;
	}
	}

[cschuchardt88]

Leveldb handle isnt disposed until FreeManagedObjects() is completed and Handle is zeroed. Even though dotnet class is disposed you can still call dispose method of a disposed class to dispose again.