TSQLite3Connection and sloTransactions
lazarus / 16-Databases

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fpcoder · 2014-02-18 02:44

The sloDesignTransactions and sloTransactions options for
TSQLite3Connection are not much documented. What are they used for?

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LacaK · 2014-02-18 10:30

Looking into code, they are not used at all.
(I do not know for what purpose they was introduced)

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fpcoder · 2014-02-20 04:22

Alright, I was just curious.

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mse · 2014-02-20 05:39

TSQLite3Connection is originally a MSEgui component. In MSEgui
tsqlite3connection has:

Code: [Select]function tsqlite3connection.cantransaction: boolean;
begin
 result:= (slo_transactions in foptions) and
    ((slo_designtransactions in foptions) or not (csdesigning in
componentstate));
end;

which is used to determine if implicit transactions are replaced by
real transactions. It is default off because SQlite3 holds a file lock
while reading a resultset which often leads to deadlocks if a
resultset is not completely loaded with tmsesqlquery.packetrecords <>
-1.

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fpcoder · 2014-02-20 06:51

Does this mean that one app can write to the SQLite database even if
another app with for example a DBGrid is connected to and showing
data? By adjusting packetrecords so all data is loaded?

Quote from: mse on February 20, 2014, 06:39:24 am..SQlite3 holds a
file lock while reading a resultset which often leads to deadlocks if
a resultset is not completely loaded with tmsesqlquery.packetrecords
<> -1.

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mse · 2014-02-20 06:57

Quote from: kapibara on February 20, 2014, 07:51:05 amDoes this mean
that one app can write to the SQLite database even if another app with
for example a DBGrid is connected to and showing data? By adjusting
packetrecords so all data is loaded?
With MSEgui components yes, I don't know how FCL handles this.