Sparse Data

Does sparse data cause significant space wastage or performance issues
in PostgreSQL?

We are building an application that stores assets. Each different type
of asset has different attributes and in initial design we decided to
store each attribute in separate tables to avoid having a lot of sparse
data. It turns out, after many revisions and working throught the asset
definitions, that are more similar than we thought, but still not very
alike. This is making me rethink splitting them out into separate
tables.

Given that PostgreSQL writes new blocks when a block changes (instead of
updating the block), it made me wonder if sparse data is really an issue
in PostgreSQL (because if it always writes a new block to replace a
block that has changed, then it wouldn't have to waste any or much
space).

Any input or knowledge would be great,

Thanks,

Jed S. Walker