0.9.1 - #transaction may wrongly end enclosing transaction

[pilcrow]

Issue

rdbi-0.9.1

RDBI::Database#transaction may incorrectly end the enclosing transaction at the conclusion of a nested transaction block, if the user has already explicitly COMMITted or ROLLBACKed the inner transaction.

Presently, #transaction, checks only to see that the dbh is within any transaction, so it cannot tell whether a block concludes in the same (possibly nested) transaction which it began.

The impact is likely limited, as nested transaction support (SAVEPOINTs?) is not to my knowledge implemented in any supported backend.

Example

Presuming a database with nested transaction support:
# initial tx depth -> 0

dbh.transaction do |dbh|    # implicit BEGIN
                            #   tx++ -> 1

  dbh.execute(SQL_1)

  dbh.transaction do |dbh|  # implicit BEGIN
                            #   tx++ -> 2
    dbh.execute(SQL_2)

    dbh.rollback            # explicit ROLLBACK:  SQL_2 undone
                            #   tx-- -> 1
  end                       # implicit COMMIT:  SQL_1 committed
                            #   ERROR - SQL_1 committed too early
                            #   tx-- -> 0

  dbh.execute(SQL_3)

  #dbh.commit               # ERROR - explicit COMMIT would be ignored here
end                         # ERROR - implicit COMMIT ignored, too
                            # ERROR - SQL_3 uncommitted

Proposed Fix

This pull request simply has #transaction remember its tx depth upon entry, and only #commit or #rollback if the depth is as expected after leaving the user block.

Tests

I have no tests for this fix.

[erikh]

Ok; I'm gonna need tests for this one, for sure.