Thanks a lot!

--- In firebird-support@yahoogroups.com, "Ivan Prenosil"
<Ivan.Prenosil@...> wrote:

>
> > Hi, I have a table with the following columns:
> >
> > ID BIGINT NOT NULL,
> > A_ID BIGINT,
> > EVENT_NUMBER BIGINT,
> > EVENT_SOURCE VARCHAR(50),
> > EVENT_TYPE SMALLINT,
> > EVENT_TIME TIMESTAMP,
> > EVENT_MESSAGE VARCHAR(10240),
> > B_ID BIGINT
> >
> > I added one record of
> > {1, 1, 1, 'abcdefghij', 1, '1/8/2006 12:00:00',
> > 'abcdefghijklmnopqrstuvwxyz1234', null}. (The character set is
> > UNICODE_FSS)
> >
> > gstat shows the record length is 556,
>
> Which is right.
>
> > which is far more than my
> > calculation of
> >
> > 4 * BIGINT + 1 * TIMESTAMP + 1 * SMALLINT + 10(/*EVENT_SOURCE*/) *
> > 2(/*UNICODE*/) + 30(/*EVENT_MESSAGE*/) * 2(/*UNICODE*/) = 122 BYTES.
> >
> > How does gstat calculate record length?
>
> gstat does not calculate anything, it just shows what it finds.
> Each row is stored in memory in its full declared length
> (for your unicode_fss varchar(10240) field it is 30720 bytes).
> Before storing it onto db page, whole row is rle compressed.
> The maximum "performance" rle can offer is that it compresses
> 128 identical consecutive bytes into 2 bytes. It means that even if your
> long field is empty it will consume at least 30720/128*2 = 480 bytes.
>
> You can find some short notes here
> http://www.volny.cz/iprenosil/interbase/ip_ib_strings.htm
>
> Ivan
>