[OT] Efficient file structure for very large lookup tables?

[Ola Fosheim Grøstad" <ola.fosheim.grostad+dlang at gmail.com>]

On Tuesday, 17 December 2013 at 19:09:49 UTC, H. S. Teoh wrote:
> What's a good, efficient file structure for storing extremely 
> large
> lookup tables? (Extremely large as in > 10 million entries, 
> with keys
> and values roughly about 100 bytes each.) The structure must 
> support
> efficient adding and lookup of entries, as these two operations 
> will be
> very frequent.

But 200*10million = 2GB. Can't you use an existing KD-tree and 
tweak it to fit memory pages and rely on paging for a start?