The logic for cancelling a savepoint was incorrect, as the behaviour
the logic was modelled on was for a different RDBMS - where a COMMIT
would always close the most recently opened transaction.
SQLite on contrast will commit the entire transaction, not just the
most recent savepoint marker until current execution point. The correct
manner to deal with a 'partial' commit is to call RELEASE <savepoint>.
This revealed an error in the savepoint logic, in that if someone had
supplied a savepoint name instead of relying on generated ones, the
rollback command did not factor for this and always assumed generated
savepoint names - again causing error. For this reason a new class
member field has been introduced to track savepoint names in a stack
fashion.
Transactions that used more than one level would cause errors if
there were consecutive calls to start a transaction - because each
query executed would clear the flag indicating that a transaction
was already in progress.
The comment for the logic to reset the nesting level on a query was
indicating that DDL (data definition language) would not work within
a transaction. This is untrue, and the module itself uses a transaction
to alter table or field names. So this function has been converted to
a no-op, deprecated to be removed in version 3 of this module. It is
also no longer called upon each query.
There have been some maintenance tidyups around this area also by
abstracting the nested transaction flag manipulations into protected
functions.
Code in the field alteration logic had a queries defiend as strings to
begin and commit transactions involve with changing table or column names.
This was causing fatal errors as BEGIN is not a valid keyword within
a trasaction (see SQLite documentation excerpt below).
A new api has been introduced to deal with transactions programmatically,
and this module was updated to support this a few months ago. This is a
tidy up of some missed portions - consuming this API which correctly uses
SAVEPOINT when a nested transaction is required automatically.
https://www.sqlite.org/lang_transaction.html
Transactions created using BEGIN...COMMIT do not nest. For nested
transactions, use the SAVEPOINT and RELEASE commands.
