Re: [sqlite] blocking - busy_timeout vs database is locked(5)

[Ray Mosley]

I have somewhat-related questions. 
1) Using the Tcl binding for SQLite 2.8, how do I even obtain the value to 
know the DB is busy?
2) If I use
 db timeout 2000
 won't the application wait until the db is free to access the db? Do I even 
need to know it was once busy if SQLite waits until it can proceed?
 Thanks from a DB rookie.

 On 8/18/05, Robert Simpson <[EMAIL PROTECTED]> wrote: 
> 
> - Original Message -
> From: "Jonathan H N Chin" <[EMAIL PROTECTED]>
> To: 
> Sent: Thursday, August 18, 2005 8:00 AM
> Subject: [sqlite] blocking - busy_timeout vs database is locked(5)
> 
> 
> [snip]
> >
> > but I still occasionally get failures:
> >
> > DBD::SQLite::db do failed: database is locked(5) at dbdimp.c line
> > 403
> >
> > Am I doing something wrong?
> >
> > What is the correct way to make accesses block/retry when the
> > database is busy?
> 
> I'm afraid you'll have to write your own internal retry mechanism. The
> busy_timeout only works in certain areas when the database is busy. When 
> an
> update is in progress however, all attempts to read will return
> *immediately* with a failure message. You'll then have to call
> sqlite3_reset() to find out what that error message is. If its a
> SQLITE_SCHEMA you need to call sqlite3_prepare() again (don't forget to
> rebind your parameters if any), and if its a SQLITE_LOCKED then you need 
> to
> sleep for some random amount of time and retry -- with hopefully an 
> eventual
> timeout mechanism in place.
> 
> Robert
> 
> 
> 


-- 
Ray Mosley

Re: [sqlite] blocking - busy_timeout vs database is locked(5)

[Robert Simpson]

- Original Message - 
From: "Jonathan H N Chin" <[EMAIL PROTECTED]>

To: 
Sent: Thursday, August 18, 2005 8:00 AM
Subject: [sqlite] blocking - busy_timeout vs database is locked(5)


[snip]


but I still occasionally get failures:

   DBD::SQLite::db do failed: database is locked(5) at dbdimp.c line 
403


Am I doing something wrong?

What is the correct way to make accesses block/retry when the
database is busy?


I'm afraid you'll have to write your own internal retry mechanism.  The 
busy_timeout only works in certain areas when the database is busy.  When an 
update is in progress however, all attempts to read will return 
*immediately* with a failure message.  You'll then have to call 
sqlite3_reset() to find out what that error message is.  If its a 
SQLITE_SCHEMA you need to call sqlite3_prepare() again (don't forget to 
rebind your parameters if any), and if its a SQLITE_LOCKED then you need to 
sleep for some random amount of time and retry -- with hopefully an eventual 
timeout mechanism in place.


Robert

Re: [sqlite] blocking - busy_timeout vs database is locked(5)

[Jonathan H N Chin]

I should perhaps note that there are only around fifty accesses in
any given five minute interval, so it is not as if anything is being
overloaded.


-jonathan

-- 
Jonathan H N Chin, 2 dan | deputy computer | Newton Institute, Cambridge, UK
<[EMAIL PROTECTED]> | systems mangler | tel/fax: +44 1223 767091/330508

"respondeo etsi mutabor" --Rosenstock-Huessy