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  1. #1
    Join Date
    May 2017
    Qt products
    Qt5 Qt/Embedded

    Default Very slow sqlite performance?

    System Info:
    OS: Debian
    Kernel: 4.4
    Platform: BeagleBoneBlack
    Sqlite3: version (SQLite version 2014-10-29 13:59:56).

    DB Info:
    Schema: CREATE TABLE Table1 (rowId INTEGER PRIMARY KEY AUTOINCREMENT, parm varchar(32), value varchar(32));
    Total Rows: 164

    If I drop into terminal, manually open DB, and issue a simple update command like (UPDATE Table1 SET value='45' WHERE parm='Parm3') it is very fast. It will occasionally lag for a second or so. I set pragma synchronous = OFF, and same with journal_mode, just to test. This makes it even faster, and I never see the occasional lag.

    So I use Qt to open the DB, set those same pragma settings, and use something like this:
    Qt Code:
    1. QSqlQuery query;
    2. QString strQuery = QString("UPDATE %1 SET value='%2' WHERE parm='%3'").arg(table).arg(value).arg(setting);
    4. QTime *time = new QTime();
    5. query.prepare(strQuery);
    6. time->start();
    8. if(!query.exec()) {
    9. qDebug() << "Error with query:: " << strQuery << "|" << query.lastError();
    10. return false;
    11. }
    13. qDebug() << "Duration::" << time->elapsed();
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    This results in an output of an elapsed time between 2000-3000 with the same simple update command? Not every time, but like 1/5 updates it will hangup for a few seconds. Again, I use the same pragma settings and update command via terminal and it runs like butter, but via Qt it seems to have a ton of overhead on ~1/5 updates. Has anyone run into this issue, or have any insight as to why this might be the case?
    Last edited by while_e; 19th September 2017 at 18:21.

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