Subject Re: [firebird-support] Varchar size overhead
Author Richard Wesley
Dmitry et alia -

On 21 Jan 2009, at 09:25, Dmitry Yemanov wrote:

> The entire record is RL compressed as a whole. And the record has
> has a
> fixed format, i.e. every column is represented with its maximum
> length.

This sounds like the contents of each record is compressed, BUT each
record still takes a fixed (maximal) amount of space on disk? That
can't be right - you add no disk read efficiency but still have to
sacrifice CPU cycles to read the data. What am I missing?

One of the reasons that I ask is I have just finished reading "Read-
Optimized Databases, In Depth" by Allison L. Holloway and David J.
DeWitt, SIGMOD 2008, which claims that using row level compression can
give a row-oriented RDBMS comparable I/O performance to a column-
oriented one with row compression (better in some cases involving
table scans and wide result tuples). If FB is using compression to
fit more rows onto database pages to reduce disk reads, that would be
awesome, but your description does not sound like that is what is
going on.
Richard Wesley Senior Software Developer Tableau