2.4.3 Retrieving caster of Unit buff or debuff - Is it possible?

[pinny]

UnitAura was not yet implemented in 2.4.3.

UnitBuff seems to be passing back the following info

1: Spell Name
2: Spell Rank
3: Spell Texture
4: ?
5: Initial Spell Duration
6: Remaining Spell Duration

Anybody have any knowledge as to how I can check which character cast the buff?

Also, I know about the COMBAT_LOG_EVENT_UNFILTERED and using that to capture the caster, but with that i'd be stuck storing everything for every unit in tables for when buffs are applied/removed which seems very inefficient and prone to errors.