[DBD-SQLite] [patch] Error handling, part 3: document sqlite-specific $sth->finish interaction with transactions and workaround error in $dbh->rollback

[kenichi ishigaki]

I'd like to turn these down, at least for now, as SQLite doc clearly
states as follows:

The ROLLBACK will fail with an error code SQLITE_BUSY if there are any
pending queries. Both read-only and read/write queries will cause a
ROLLBACK to fail. A ROLLBACK must fail if there are pending read
operations (unlike COMMIT which can succeed) because bad things will
happen if the in-memory image of the database is changed out from
under an active query.
(http://sqlite.org/lang_transaction.html)

And DBI doc also says

    When all the data has been fetched from a "SELECT" statement, the
    driver will automatically call "finish" for you. So you should *not*
    call it explicitly *except* when you know that you've not fetched all
    the data from a statement handle *and* the handle won't be destroyed
    soon.

This rolling-back an unfinished query is obviously one of such
exceptional cases.

These patches also have side effects that probably surprise users. I
think it's better for you to add $sth->finish explicitly before you
call $sth->rollback for a reading query.

Regards,

Kenichi

2011/10/15 Yuriy Kaminskiy <yumkam at mail.ru>:
> In sqlite, ROLLBACK fails with SQLITE_BUSY when there are active/unfinished
> SELECT statements.
> As DBI's $dbh->rollback cannot handle errors in sane way, add workaround to
> reset all sth and retry when $dbh->rollback fails with SQLITE_BUSY.
>
> PS For whatever reasons, "Error handling, part 2" cannot be sent to list
> (disappear into /dev/null without any diagnostics) :-|
> Will retry in few days if it won't appear in gmane or list archives.
>
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