The string cache is only very seldom written but very often read. To
improve thread scaling it is faster to lock it only for write operations.
So we use a shared mutex which is locked in shared mode for read
operations and locked exclusively for write operations.
Change-Id: I2cc742d1b9cc15c162be40ab339fa8310640bc44
Reviewed-by: Tim Jenssen <tim.jenssen@qt.io>
If you use the database in a multi-threaded environment, you must always
your statements in transactions.
For read-only statements, you use DeferredTransaction and write statements
you use ImmediateTransaction. If you mix read and write statements you have
to use ImmediateTransaction. Don't use DeferredTransaction because it leads
to undefined behavior.
Change-Id: Ida298a20f33423c8da09e768a7b658dd8e918f46
Reviewed-by: Tim Jenssen <tim.jenssen@qt.io>
Reviewed-by: Marco Bubke <marco.bubke@qt.io>
