Re: "database is locked" on first commit?

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Dennis Lee Bieber wrote:
> [http://www.sqlite.org/lockingv3.html]
> """
> In autocommit mode, all changes to the database are committed as soon as
> all operations associated with the current database connection complete.
> """"
> 
> ... what is meant by "the current database connection complete"? Is that
> the same as a con.close() in pysqlite2? I can't say... (and since I run
> from prebuilt binaries, I can't browse source code to the library to
> tell)

No, this just means that in autocommit mode, SQLite will transform any DML
statement, like:

UPDATE foo SET bar=42 WHERE ...

INTO

BEGIN
UPDATE foo SET bar=42 WHERE ...
COMMIT

I. e. it will implicitly wrap each statement executed into a transaction.

> 	At this juncture... I'd probably revert to wolf-fencing... (wrap
> each .execute() and .fetch() with a pair of logging calls -- and see if
> the log shows something like:
> 
> thread-m: execute: select
> thread-n: execute: update (insert, delete)
> thread-n: time-out
> 
> ... rather than something like:
> 
> thread-m: execute: select
> thread-n: execute: update
> thread-m: execute complete
> thread-n: ...

Let's hope this works. You can perhaps implement that simpler by using
pysqlite's factories. I've attached a quick example.

- -- Gerhard
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from pysqlite2 import dbapi2 as sqlite
from logging import debug
import logging
debug = logging.debug

class LoggingConnection(sqlite.Connection):
    def commit(self):
        debug("COMMIT")
        sqlite.Connection.commit(self)

    def rollback(self):
        debug("ROLLBACK")
        sqlite.Connection.rollback(self)

    def cursor(self, *args):
        return LoggingCursor(self, *args)

class LoggingCursor(sqlite.Cursor):
    def execute(self, sql, *args):
        debug("EXECUTE " + sql)
        sqlite.Cursor.execute(self, sql, *args)

    def executemany(self, sql, *args):
        debug("EXECUTEMANY " + sql)
        sqlite.Cursor.executemany(self, sql, *args)


import sys
logging.basicConfig(level=logging.DEBUG, stream=sys.stderr)
con = sqlite.connect(":memory:", factory=LoggingConnection)

con.execute("create table t(x,y,z)")
con.execute("insert into t(x) values (5)")
con.rollback()

con.execute("insert into t(x) values (4)")
con.commit()

con.execute("select * from t")