Slow loading of UITableView. How know why?

Question

I have a UITableView that show a long list of data. Use sections and follow the sugestion of http://stackoverflow.com/questions/695814/how-solve-slow-scrolling-in-uitableview .

The flow is load a main UITableView & push a second selecting a row from there.

However, with 3000 items take 11 seconds to show. I suspect first from the load of the records from sqlite (I preload the first 200). So I cut it to only 50.

However, no matter if I preload only 1 or 500, the time is the same.

The view is made from IB and all is opaque.

I run out of ideas in how detect the problem. I run the Instruments tool but not know what to look.

Also, when the user select a cell from the previous UITable, no visual feedback is show (ie: the cell not turn selected) for a while so he thinks he not select it and try several times. Is related to this problem.

What to do?

NOTE: The problem is only in the actual device:

• iPod Touch 2d generation
• Using fmdb as sqlite api
• Doing the caching in viewDidLoad
• Using NSDictionary for the caching
• Using a NSAutoreleasePool for the caching part.
• Only caching the row ID & mac 4 fields necesary to show the cell data
• UIView made with interface builder, SDK 2.2.1
• Instruments say I use 2.5 MB in the device

Answer 1

The -[FMResultSet next] call can be a very expensive call to make, depending on the data that's getting loaded. It'd during this call that sqlite is actually going to the database, finding the next row to return, and giving you back the appropriate fields. It's not just an enumerator.

You might want to consider pre-caching all of the data before actually displaying the table. This means that you would do all of your FMDB calls before the table gets shown on the screen.

If that takes too long, you might want to show the tableview with its initial rows, and then use NSOperations or just a second thread to load the data in the background and cache it that way.