Re: vacuum, performance, and MVCC, and compression

> What about increasing the size of an existing index entry? Can that be
> done easily when a new row is added?

I'd say it looks pretty much like inserting a new index tuple...
Say "value" is the indexed column.

Find first page in the index featuring "value".
1 If there is space on the page,
add the tuple id to the list of the corresponding index entry (just like
creating a new index tuple, but uses less space).
else
look at next page.
If next page has an index tuple with the same indexed value,
goto 1
else
insert new page and create an index tuple on it

> I would be worried about the overhead of doing that on compression and
> decompression.

The compression methods mentioned in the article which was passed on the
list seemed pretty fast. From IO-limited, the test database became
CPU-limited (and a lot faster).