QSql*Model are very slow

Hi all.
I have rather big database (20000 records with 17 columns each).
I use QSqlTableModel to display that base. However, when i try to scroll using scroll bar, my treeView lags (for about 1-2 seconds). Seems it lags when first time calling data() method to retrieve data from database. After fields are cached to view, i can scroll without any lags. How can i fix lagging for first call or at least precache data to view?
P.S.: same lags when using QueryModel
P.P.S.: also i have lag when model does fetchMore(), but it can be fixed by fetching all model.

The only viable solution is to create a custom model that will fetch rows manually using a worker thread.

Well, even after fetching model i have lags when accessing elements for the first time. So thread on fetching will not help i think.

It will help.

Well, after some tests it appears that loop

Code:

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while (model->canFetchMore())
        model->fetchMore();

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takes very little time.
However, showing treeview with model that is already fetched takes about 7-10 seconds. So, threading fetching won't help me, isn't it?

It will help. If you do it wisely, of course.

why are you using a qtreeview instead of a qtableview?

anyway...
I don't understand your "lag"....

Just right now I'm working with a query with 15000 records... (qsqlquerymodel + qtableview) and it's pretty fast.

I think that you have another problem.

(¿are you using a subclassed view or model?? )

The problem was in QTreeView. Using QTableView has no problems (lags are very little on sorting, about 0.3 sec, which is acceptable and no lags on scrolling). Thanks all.

Not to create new thread.
Is it correct that my own table model will always be faster than sql model when showing all data/sorting it?
And what about filtering with ProxyModel - will it be faster or slower than filtering with sql query?

It depends. If the database is not optimized in some special way for sorting in a particular order, doing it locally will probably be faster.

It is optimised. I choose myself the format of database. I only need to take decicion - to use sql database and classes for it or implement everything myself (storing in memory, sorting, filtering, editing).

Quote:

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Originally Posted by ABBAPOH

It is optimised.

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And based on what do you say that? You can't possibly know that upfront unless you implemented the database engine yourself.

I meant i created indexes in sql table and not try to sort not indexed columns))
however yes, sqlite driver implementation can be rather slow, however i hope it is not.

I tested sorting methods with different model implementations (SqlTableModel, SqlQueryModel + Proxy, custom model with data in memory + Proxy for sorting). Seems true, however i thought sql will be faster:)

Quote:

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Sorting... time elapsed: 150 ms - OwnModel + Proxy model
Sorting... time elapsed: 60 ms - OwnModel + Proxy model reverse
Sorting... time elapsed: 421 ms - SqlTableModel + fetchall
Sorting... time elapsed: 391 ms - SqlTableModel reverse + fetchall
Sorting... time elapsed: 1076 ms - SqlTableModel not indexed column + fetchall
Sorting... time elapsed: 236 ms - SqlQueryModel fetched + Proxy model
Sorting... time elapsed: 99 ms - reverse

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Sql might be faster only if you request data in the order that it is stored in the engine. That's what I meant by being optimized for sorting in some particular order.