SQLiteDatabase throws SQLiteReadOnlyDatabaseException on writeable database

Question

The following code snippet is supposed to remove duplicates from a SQLite table:

public int removeDuplicates(String table, String column, String idcolumn) {
    if (mDB.isReadOnly()) return -1;
    String idcol = idcolumn == null ? "_id" : idcolumn;
    String sql = String.format(Locale.US, "DELETE from %s where %s in " + "(select %s from %s JOIN "
            + "(select min(%s) as id_keep,%s,count(*) as dups from %s group by %s) AS A "
            + "ON A.%s=%s.%s where %s<>id_keep)", table, idcol, idcol, table, idcol, column, table, column, column,
            table, column, idcol);
    SQLiteStatement sqlcmd = mDB.compileStatement(sql);
    int result = sqlcmd.executeUpdateDelete();
    return result;
}

The problem is that a SQLiteReadOnlyDatabaseException gets thrown, even though it passes the !db.isReadOnly() test.

I don't think this problem is related to this question since everything is compiled against ICS; and other apps (using a ContentProvider driving the queries) are able to write to the DB.

The DB is in a public folder on the SD card.

The stack trace is:

11-02 14:48:24.596 E/AndroidRuntime(12324): android.database.sqlite.SQLiteReadOnlyDatabaseException: attempt to write a readonly database
11-02 14:48:24.596 E/AndroidRuntime(12324):     at android.database.sqlite.SQLiteStatement.native_executeSql(Native Method)
11-02 14:48:24.596 E/AndroidRuntime(12324):     at android.database.sqlite.SQLiteStatement.executeUpdateDelete(SQLiteStatement.java:90)
11-02 14:48:24.596 E/AndroidRuntime(12324):     at android.database.sqlite.SQLiteDatabase.executeSql(SQLiteDatabase.java:1899)
11-02 14:48:24.596 E/AndroidRuntime(12324):     at android.database.sqlite.SQLiteDatabase.execSQL(SQLiteDatabase.java:1839)
11-02 14:48:24.596 E/AndroidRuntime(12324):     at android.database.sqlite.SQLiteDatabase.beginTransaction(SQLiteDatabase.java:661)
11-02 14:48:24.596 E/AndroidRuntime(12324):     at android.database.sqlite.SQLiteDatabase.beginTransactionNonExclusive(SQLiteDatabase.java:576)
11-02 14:48:24.596 E/AndroidRuntime(12324):     at android.database.sqlite.SQLiteStatement.acquireAndLock(SQLiteStatement.java:247)
11-02 14:48:24.596 E/AndroidRuntime(12324):     at android.database.sqlite.SQLiteStatement.executeUpdateDelete(SQLiteStatement.java:84)
11-02 14:48:24.596 E/AndroidRuntime(12324):     at za.co.nimbus.druids.DatabaseTools.removeDuplicates(DatabaseTools.java:139)

Any ideas?

You stated the database is in a public folder on the SD card. Does your app have permission to write to the SD? <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" /> — mah
– mah, Commented Nov 2, 2012 at 12:59
Have you created your DB instance as writable like this : SQLiteDatabase database = this.getWritableDatabase(); — Kartihkraj Duraisamy
– Kartihkraj Duraisamy, Commented Nov 2, 2012 at 13:10
Son of a $%$@! @mah, you got it! I've been stuck on this for hours. Thanks. what a pity Android couldn't throw a more enlightening exception — CjS
– CjS, Commented Nov 2, 2012 at 14:38

mah · Accepted Answer · 2012-11-02 14:39:08Z

1

In order to write to a database that lives on SD, you'll need to have permission to write to external memory. Simply add the following to your manifest:

<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />

answered Nov 2, 2012 at 14:39

mah

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