QSqlQueryModel tweaks?

[baray98]

I have an SQL stement that will return millions of record ie


select * from myTable


i noticed that this will take sometime to see it on my QTableView. now my question is . Where can i possibly tweak it to make it faster?

My opinion:

I think QSqlQueryModel is caching just 256 records at a time , and model to view will take no time at all. I think its really the database that is taking the time to "build" those records for me. If theres in any other path that i can work on to make it a bit faster please enlighten me...

by the way my database is MS SQL

baray98

[wysota]

Use QSqlTableModel, there is a chance it will be faster. If not then you can't use such a simple model and need to ask the database for just part of the data at a time. Also have a look at this: http://blog.wysota.eu.org/index.php/2006/12/26/remote-models/

[baray98]

wysota,

may i know why you think QSqlTableModel would be faster than QSqlQueryModel if you don't mind.

baray98

[wysota]

As far as I remember the query model downloads all rows from the query result at once and the table model fetches rows as they are needed but I may be wrong.

[ChrisW67]

I found the same behaviour with QSqlTableModel (which is built atop QSqlQueryModel anyway) on Sqlite databases. The QTableView displays the first 255 (model's QSQL_PREFETCH value) rows and scales its vertical scroll bar for that number (the model is returning a rowCount()==255). When you drag the scroller down you get a long pause as the model fetches another 255 rows and rescales the scroll bar. It will keep doing this until all rows are fetched. The only way I found to have smooth end-to-end scrolling was to do:

while (model->canFetchMore()) model->fetchMore(); which is acceptable for a few thousand rows but not (probably) a few million.

[baray98]

I visited your blog http://blog.wysota.eu.org/index.php/...remote-models/ and tried your remotemodel and I think its a cool idea for my case and you mentioned you've tried it in some SQL database too.

If its not too much I am wondering if you can share a snippet of your model accessing SQL database so I can test if it will improve my problem.

baray98