Question

I have done some measurements regarding the IO on my SQLite database. It takes around 6 seconds to load some object from this database. I have a class which extends Asynctask, this class job is to load the last 10 entries in my database. This class is constructed this way:

import View.CustomAdapter;
import android.app.ProgressDialog;
import android.content.Context;
import android.os.AsyncTask;
import android.widget.ListView;
import android.widget.ProgressBar;
import android.widget.TextView;
import android.util.Log;
import android.view.*;

public class LoadCases extends AsyncTask<String, Integer, ArrayList<Case>> {

    ProgressBar progressBar;
    ArrayList<Case> lastTenCases; 
    CustomAdapter cAdapter; 
    Context context;
    ListView lastCases;
    DatabaseHandler db;
    TextView loading;
    int options;

    public LoadCases(ProgressBar progressBar, Context context, ListView lastCases, TextView loading, ArrayList<Case> lastTenCases) {
        this.progressBar = progressBar;
        this.context = context;
        this.lastCases = lastCases;
        this.loading = loading;
        this.lastTenCases = lastTenCases;
        db = new DatabaseHandler(context);
    }

    public void onPreExecute() {
        progressBar.incrementProgressBy(1);
    }


    @Override
    protected ArrayList<Case> doInBackground(String... params) {
        long start = System.nanoTime();
        lastTenCases = db.getAllCases(10);
        long end = System.nanoTime();
        Log.d("TIME TO LOAD CASES FROM BASE: ", Long.toString((end-start)/1000000000)); 
        return lastTenCases;
    }

    public void onPostExecute(ArrayList<Case> result) {
        progressBar.setVisibility(View.GONE);
        loading.setVisibility(View.GONE);
        cAdapter = new CustomAdapter(context, lastTenCases);    
        cAdapter.notifyDataSetChanged();
        lastCases.setAdapter(cAdapter); 

}
}

As you may see, the measurements is done just before I call the method getAllCases(10)

long start = System.nanoTime();
lastTenCases = db.getAllCases(10);
long end = System.nanoTime();
Log.d("TIME TO LOAD CASES FROM BASE: ", Long.toString((end-start)/1000000000)); 

This will give me about 6 seconds to load 10 cases from the database, as I mentioned earlier.

Now, over to the getAllCases method

public ArrayList<Case> getAllCases(int take) {

    ArrayList<Case> caseList = new ArrayList<Case>();
    String selectQuery = "SELECT  *, (strftime('%s', DATE) * 1000) AS DATENOW FROM " + TABLE_CASES + " ORDER BY " + DATE + " DESC LIMIT " + Integer.toString(take) + " ;";

    SQLiteDatabase db = this.getWritableDatabase();
    Cursor cursor = db.rawQuery(selectQuery, null);

    // looping through all rows and adding to list
    if (cursor.moveToFirst()) {
        do {
            Case c = new Case();

            long millis = cursor.getLong(cursor.getColumnIndexOrThrow("DATENOW"));
            Date addedOn = new Date(millis);
            c.setCaseNumber(cursor.getString(0));
            c.setDate(addedOn.toLocaleString());
            c.setStatus(cursor.getString(cursor.getColumnIndex(STATUS)));
            caseList.add(c);
        } while (cursor.moveToNext());
    }
    cursor.close();
    db.close();
    return caseList;
}

This method will construct Case objects, and add this to an ArrayList. This ArrayList will be return. Yeah, I guess you understand the code. But 6 seconds, really? What am I doing wrong? How can I speed up this operation?

Thanks!

Answer 1

It depends on Your database structure (e.g. if TABLE_CASES is just another complex query) and number of fields in TABLE_CASES, but at least the following points might be improved:

• strftime('%s', DATE) * 1000) – do You really need to calculate it every time when You need to get CASE? Storing of that value instead of calculation will definitely speed up the query;
• Not sure if ArrayList needed, probably CursorLoader could be used;
• Based on this tip calling of new Date(millis) probably should be moved out of the loop;
• Calls to getColumnIndexOrThrow and getColumnIndex should be also moved out of the loop;
• toLocaleString is deprecated in API level 1 please use DateFormat

Finally, I would suggest to follow this guide for traceview and determine if the delay actually happens in SQLite or in the loop just after it.