[Lazarus] Is there a way to NOT use a transaction in sqldb ?

[Alexsander Rosa]

It's weird to *require* a COMMIT on a simple SELECT, but the CommitRetaining
trick seemed to work. The system table "pg_stat_activity" still shows the
"<IDLE> in transaction" pending query but the lock is no more -- at least I
could execute a CREATE TABLE normally.

2009/10/13 Michael Van Canneyt <michael at freepascal.org>

>
>
> On Tue, 13 Oct 2009, Alexsander Rosa wrote:
>
>  I'm using Lazarus from SVN with FPC 2.2.4 under Ubuntu 9.04 connecting to
>> an 8.3 PosgreSQL server.
>>
>> I need to use it in a program that stays open all day -- it's a price
>> check terminal. The user can read a barcode to show data about a single
>> product or type
>> part of a description and browse the resulting list. This list is a DBGrid
>> whose TSQLQuery's DataSet stays open while the user browses (or simply
>> abandon the
>> terminal). It's a SELECT that does not change anything, it does not need a
>> transaction. With the required transaction, there's always an "<IDLE> in
>> transaction" query open when the Lazarus application is running:
>>
>> select datname, usename, query_start, procpid, client_addr from
>> pg_stat_activity where current_query = '<IDLE> in transaction';
>>
>> This transaction locks the changes in the database structure so you can't,
>> for example, create a new table with a foreign key. A mere CREATE TABLE with
>> a
>> FOREIGN KEY referring to an existing table would take forever waiting for
>> that lock to be released.
>>
>
> Did you try calling  "CommitRetaining" on the transaction ? It will commit
> the transaction (and so free the lock), but should keep the dataset open ?
>
> If you want the transaction closed (no transaction active), then you'll
> have to transfer the results of the query to a list (TCollection) and show
> the collection in the grid, because committing the transaction closes any
> dataset associated with it.
>
> Michael.
>
> --
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-- 
Atenciosamente,
Alexsander da Rosa
Linux User #113925

"Extremismo na defesa da liberdade não é defeito.
Moderação na busca por justiça não é virtude."
-- Barry Goldwater
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