Subject Re: [firebird-support] About firebird performance
Author Alexey Kovyazin
Hi Hector,

So you finally decided to try Firebird - that's good.

I think that you are facing garbage collection problem - if there are a lot of record versions in the TABLE1 which are not interested to any transaction, your query will force garbage collection, and it can take some time.

How to check? run SELECT count(*) twice and compare execution times, and other query statistics (reads/writes).

Also, run gstat -a -r <database> and check information for TABLE1 - VERSIONS and MAX VERSIONS, if there are big numbers there, problem is certainly related with record versions, with the initial cause in wrong transactions management - i.e., long-running write transactions or forced rollbacks.

Alexey Kovyazin


I'm doing some basic tests with Firebird and I'm facing something I
cannot understand (I'm a newbie to Firebird which has worked with
IB7.5 for years, so I apologize if I ask something obvious):

- I have a linux server with firebird 2.5.4 Superserver: multi-core (4), 3GB RAM
- I placed a "huge" database: 1000 tables, 9GB
- When I issue a query like this "select count(*) from TABLE1" it
takes very long time to complete (>30 min).
- TABLE 1 has 3 million records

As I told you, I'm quite used to IB7.5, but I guess this is not normal
at all...probably I'm missing something but I couldn't find any
document which gives me an idea of what I'm doing wrong.

With same hardware an IB7.5 same query took 40 sec to complete (first
time issued, no cache).

Could anyone help?

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