On 09/12/2018 08:56 PM, Nic Ramage wrote:
Hi,
I think I have found a regression/bug in Sqlite with respect to
the sqlite3_get_autocommit() function.
Hi,
Thanks for putting in the work to create the bug demo. Bisecting the
latest SQLite commits using it shows that this bug was fixed here:
https://www.sqlite.org/src/info/e6108047cb136119
Fix will appear in 3.25.0 (currently undergoing release testing).
Dan.
Sometimes, when multiple connections are used in multiple threads,
sqlite3_get_autocommit() reports that the connection has a transaction
open (i.e. not in auto commit mode), even though sqlite3_step() returns
SQLITE_BUSY. I have verified that sqlite3_get_autocommit() reports that
there is no transaction open before sqlite3_step() is called. The problem
seems to be specific to the WAL journal mode, as I haven't been able to
reproduce it for
Initially, the problem only showed up under Linux, but I have now been able
to reproduce the problem on Windows too. For me it shows up quicker under
linux, but that may just be because of the difference in environments. I
have attached a single-file C++11 application that consistently reproduces
the problem for me.
I was also able to bisect the introduction of the problem to sqlite
v3.17.0. v3.16.2 does not have the problem. The latest 3.24.0 release
does. I am not an expert on the sqlite source code, but during my
debugging, I was able to determine that the auto commit flag was being
cleared in "case OP_AutoCommit", which returns without error. Obviously,
something else must be causing the SQLITE_BUSY afterwards, but is not
resetting the auto commit flag.
In my code, I have worked around the problem by issuing a "rollback"
whenever I detect the problem described.
I hope this is enough information to be able to solve the bug. If,
however, this behaviour turns out not to be a bug, but something that is
expected to happen occasionally, then the "rollback" provides a reasonable
way to mitigate the issue.
Regards
Nic
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