Good morning Karol,

yes, storing big data chunks outside database file is an opinion we
regularly use, too. It has the serious disadvantage, that you've to deal
with different addressing and right schemes on different operating
systems and deployment environments (local/remote servers, UNC-paths
etc) and with particular backup mechanisms to keep everything
consistent, though.

You are right: Blobs are stored in separate pages. But having blob
fields inside tables with other fields forces these pages to be
allocated when record is created - whether the blob will contain data or
not. Furthermore, common (bad) practice of fetching all fields (select *
from), sometimes even performed by database access layer of programming
language against the developers wish, accesses this data and decreases
performance.

Thus, having blobs stored in different table(s) usually leads to better
performance, because blob access is more evident and people (hopefully)
think twice before fetching...

Regards, Thomas

> But you also misunderstud advice.
> Blobs are not stored in table with its other fields. In record exists
> only blob id and blob is stored on separate pages. Then moving it to
> separate table do nothing.
>
>
> But i always prefere store big data like document scans outside of
> database and in main database have only some hint about file name
> without final location.
>
> Only application have knowlage about final location and can load document
>
> Regards,
> Karol Bieniaszewski
>
> ----- Reply message -----
> Od: "Thomas Beckmann" <thomas.beckmann@...>
> Do: <firebird-support@yahoogroups.com>
> Temat: [firebird-support] Request for advice
> Data: pt., kwi 25, 2014 00:46
>
>
>
>
> As I fear, some people misunderstood Frank's hints, I'd like to clarify:
> I know no reason to store blobs in data table with other objects data,
> it should be stored in separate table(s).
>
> This does not (significantly) grow database, does not make it
> significantly slower and does not have any impact on backup/restore: But
> performs ways better, if blob fields are not main data fields.
>
> This "optimization" has completely different impacts than moving blob
> data to a different database: Not only that every select has to be
> evaluated on runtime by execute statement, it has to be fetched from
> "far" destination (with no optimization hints), and there are no means
> to keep referential integrity by database design between the two databases.
>
> Thomas
>
> Am 25.04.2014 00:29, schrieb Alexandre Benson Smith:
>>
>>
>> Em 24/4/2014 17:08, Mark Rotteveel escreveu:
>>> On 24-4-2014 20:49, Frank Schlottmann-Gödde wrote:
>>>> As a compromise, I would suggest to place your blobs into a separate
>>>> table, it will increase the size of your main database, but will also
>>>> speed up the acccess to your blobs without interfering with everyday
>>>> database operations.
>>> As most blobs are stored out of band, I would expect that moving them to
>>> a separate table this doesn't have a big impact unless you have the
>>> habit of always retrieving and loading all fields of a table.
>>>
>>> Mark
>>
>> If the blob's are small enough to fit into the data page, it will
>> dramatically reduce the number of records per page, and ever if you
>> don't select it you will read the whole page, where most part of it is
>> the blob content.
>>
>> Moving the blob to a separate table would reduce this.
>>
>> see you !
>>
>>
>
> --
> Mit freundlichen Grüßen,
>
> Thomas Beckmann
> Diplom-Informatiker
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--
Mit freundlichen Grüßen,

Thomas Beckmann
Diplom-Informatiker


Wielandstraße 14c • 23558 Lübeck
Tel +49 (22 25) 91 34 - 545 • Fax +49 (22 25) 91 34 - 604
Mail thomas.beckmann@... <mailto:thomas.beckmann@...>

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