[Lazarus] Database access and thread-safety

Mark Morgan Lloyd markMLl.lazarus at telemetry.co.uk
Mon Nov 8 10:19:31 CET 2010

Michael Van Canneyt wrote:
> On Mon, 8 Nov 2010, Mark Morgan Lloyd wrote:
>> Can anybody say whether a TSQLQuery can be activated in a thread, 
>> provided that the portions of the app which activate it and the 
>> portions which read data from it are protected by critical sections?
>> I'm trying to increase the responsiveness of a program that I'm using 
>> as a testbed before moving onto anything critical. Backend is 
>> PostgreSQL accessed via a TPQConnection.
> If the postgres client library is thread safe, then SQLDB (and in 
> particular
> TSQLQuery) should also be thread safe.

Thanks Graeme and Michael, that's encouraging. I'm not planning to use 
any graphical DB-aware controls, or if I do I'll have an in-memory 
database as a buffer.

My normal preference would have been to use ODBC or similar to improve 
portability. However in the current case I want to use the 
PostgreSQL-specific LISTEN/NOTIFY facility to save having to poll the 
database for changes, I haven't yet worked out whether I can get at that 
easily but I'm pretty sure that using a generic connection layer would 
complicate things.

Mark Morgan Lloyd
markMLl .AT. telemetry.co .DOT. uk

[Opinions above are the author's, not those of his employers or colleagues]

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