Question

I’m developing an application that tracks the user’s current position and stores it into a SQLite database. Everything works fine, but now I have the problem when querying the database for a track with more than 1000 records it takes nearly 1.5 minutes. On my Desktop it just takes 1 second.

I know it’s a query with many subselects but I wasn’t able to get the right result another way. In my opinion this belongs to the aggregate functions like avg() and sum().

Here’s my query:

Cursor c = readableDB
    .rawQuery(
            "SELECT DISTINCT t._id , title , strftime('%Y-%m-%d' , starttime , 'unixepoch' , 'localtime') as date , description, "
            + "round((SELECT sum(distToPrev)/1000 FROM positions p WHERE p.trackid=t._id) , 2) as distance , " 
            + "(SELECT count(latitude) FROM positions p WHERE p.trackid=t._id) as waypoints, "
            + "(SELECT (avg(speed)*3.6) FROM positions p WHERE p.trackid=t._id) as avgspeed, "
            + "(SELECT (max(speed)*3.6) FROM positions p WHERE p.trackid=t._id) as maxspeed, "
            + "(SELECT sum(altitudeUP) FROM positions p WHERE p.trackid=t._id) as climb , "
            + "(SELECT avg(heartbeat) FROM heartbeats h WHERE h.trackid=t._id) as avgheartbeat , "
            + "(SELECT max(heartbeat) FROM heartbeats h WHERE h.trackid=t._id) as maxheartbeat , "
            + "(SELECT avg(cadence) FROM heartbeats h WHERE h.trackid=t._id) as avgcadence "
            + "FROM tracks t LEFT JOIN heartbeats h ON t._id = h.trackid WHERE t._id = ?",
            new String[]{String.valueOf(trackId)}); 
    c.moveToFirst();

How can I optimize this query? I tried it already this way, but then the result was wrong and it took the same amount of time.

SELECT t._id , title , strftime('%Y-%m-%d' , starttime , 'unixepoch' , 'localtime') as date , description,
sum(distToPrev)/1000 as distance ,
count(latitude) as waypoints, 
(avg(speed)*3.6) as avgspeed, 
(max(speed)*3.6) as maxspeed, 
sum(altitudeUP) as climb , 
avg(heartbeat)  as avgheartbeat ,
max(heartbeat)  as maxheartbeat ,
avg(cadence) as avgcadence 
FROM tracks t 
LEFT JOIN heartbeats h ON t._id = h.trackid 
INNER JOIN positions p ON t._id = p.trackid 
     WHERE t._id = ?

Since 2 hours I’m looking for a solution and I don’t know what I’m doing wrong. Maybe I have to take a break.

EDIT:

Here my create statements:

CREATE TABLE heartbeats(_id INTEGER PRIMARY KEY AUTOINCREMENT, trackid INTEGER NOT NULL, heartbeat INTEGER NOT NULL, cadence INTEGER, timestamp TIMESTAMP);


CREATE TABLE positions(_id INTEGER PRIMARY KEY AUTOINCREMENT, trackid INTEGER NOT NULL, longitude REAL NOT NULL, latitude REAL NOT NULL, altitude REAL, altitudeUP REAL, speed REAL, accuracy REAL, distToPrev REAL, timestamp TIMESTAMP);


CREATE TABLE tracks(_id INTEGER PRIMARY KEY AUTOINCREMENT, title TEXT NOT NULL, description TEXT, starttime DATETIME NOT NULL, endtime DATETIME);

Answer 1

This will do the job:

SELECT tid, date, waypoints, avg(heartbeat) AS avgheartbeat 
FROM (SELECT t._id AS tid, strftime('%Y-%m-%d' , starttime , 'unixepoch' , 'localtime') AS date, count(latitude) AS waypoints
         FROM tracks t LEFT JOIN positions p ON t._id = p.trackid  
         WHERE t._id = ?
         GROUP BY t._id , strftime('%Y-%m-%d' , starttime , 'unixepoch' , 'localtime'))
    LEFT JOIN heartbeats h ON tid = h.trackid
GROUP BY tid, date, waypoints

Add fields as required.