Joost van der Sluis wrote:
PostgreSQL gets "locked", I mean, the tables being used by sqldb can't
be modified (new columns, new constraints, etc) while the sqldb
connection is active, even if it's a read-only SELECT. If someone is
testing a heavy report the tables affected can't be changed by the DBA
-- it's a major headache.
Thing is, that TSQLQuery by default fetches only the first 10 records,
and then keeps the cursor open, so when you need more records, those are
fetched too. Setting PacketRecords to -1 will make it fetch the complete
table at once.
But then still, you have the data fetched in memory, so if you want to
change the data, and apply changes, you have to keep the transaction
open. (Well, it's up to you. But think through what you're doing)
And I assume that Postgres (don't remember exactly) can set the behavior
of transactions. Apparently they are blocking by default.
Various parameters to begin transaction, set transaction and lock. It's
a few years since I've fiddled with these and I only did it by hand,
i.e. fed explicit commands through BDE to the server.
If I could ask: where can I find a description of how TSQLQuery etc.
should be used for non-trivial applications? For example, if I want to
set up an explicit transaction, insert a few hundred rows of data, and
then make an explicit decision on whether I commit or rollback?
I can see TSQLQuery.InsertSQL etc., but how should they be used? If I
want to force a lock on a table how should I do it?
--
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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