How to tell if sqlite database file is valid or not - database

Question

In the code below, pathToNonDatabase is the path to a simple text file, not a real sqlite database. I was hoping for sqlite3_open to detect that, but it doesn't (db is not NULL, and result is SQLITE_OK). So, how to detect that a file is not a valid sqlite database?
sqlite3 *db = NULL;
int result = sqlite3_open(pathToNonDatabase, &db);
if((NULL==db) || (result!=SQLITE_OK)) {
// invalid database
}

Answer 1

sqlite opens databases lazily. Just do something immediately after opening that requires it to be a database.
The best is probably pragma schema_version;.
This will report 0 if the database hasn't been created (for instance, an empty file). In this case, it's safe work with (and run CREATE TABLE, etc)
If the database has been created, it will return how many revisions the schema has gone through. This value might not be interesting, but that it's not zero is.
If the file exists and isn't a database (or empty), you'll get an error.
If you want a somewhat more thorough check, you can use pragma quick_check;. This is a lighter-weight integrity check, which skips checking that the contents of the tables line up with the indexes. It can still be very slow.
Avoid integrity_check. It not only checks every page, but then verifies the contents of the tables against the indexes. This is positively glacial on a large database.

Answer 2

For anyone needing to do this in C# with System.Data.SQLite you can start a transaction, and then immediately roll it back as follows:-
private bool DatabaseIsValid(string filename)
{
using (SQLiteConnection db = new SQLiteConnection(#"Data Source=" + filename + ";FailIfMissing=True;"))
{
try
{
db.Open();
using (var transaction = db.BeginTransaction())
{
transaction.Rollback();
}
}
catch (Exception ex)
{
log.Debug(ex.Message, ex);
return false;
}
}
return true;
}
If the file is not a valid database the following SQLiteException is thrown - file is encrypted or is not a database (System.Data.SQLite.SQLiteErrorCode.NotADb). If you aren't using encrypted databases then this solution should be sufficient.
(Only the 'db.Open()' was required for version 1.0.81.0 of System.Data.SQLite but when I upgraded to version 1.0.91.0 I had to insert the inner using block to get it to work).

Answer 3

I think a pragma integrity_check; could do it.

Answer 4

If you want only to check if the file is a valid sqlite database then you can check with this function:
private bool CheckIfValidSQLiteDatabase(string databaseFilePath)
{
byte[] bytes = new byte[16];
using (FileStream fileStream = new FileStream(databaseFilePath, FileMode.Open, FileAccess.Read))
{
fileStream.Read(bytes, 0, 16);
}
string gg = System.Text.ASCIIEncoding.ASCII.GetString(bytes);
return gg.Contains("SQLite format");
}
as stated in the documentation:
sqlite database header