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database/sql: Transaction commit closes the transaction even if there was an error on commit. #7777

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gopherbot opened this issue Apr 14, 2014 · 5 comments

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@gopherbot
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@gopherbot gopherbot commented Apr 14, 2014

by Thetawaves:

What steps reproduce the problem?
If possible, include a link to a program on play.golang.org.

1. Using the sqlite driver, start a long running query.
2. Attempt to insert a row into the same table you queried.
3. Attempt to commit the insert transaction. The commit will fail because of a lock on
the table.

This is fine except that the transaction commit function in database/sql closes the
database/sql transaction through the use of defer tx.close() even if the commit was
unsuccessful. I have not been able to regain control of this transaction once the
database/sql representation has closed.


What should have happened instead?

The database/sql transaction commit function should first attempt to commit the driver
transaction, and only if it has succeeded, close the database/sql representation.

The function in question:

  1058  // Commit commits the transaction.
  1059  func (tx *Tx) Commit() error {
  1060      if tx.done {
  1061          return ErrTxDone
  1062      }
  1063      defer tx.close()
  1064      tx.dc.Lock()
  1065      defer tx.dc.Unlock()
  1066      return tx.txi.Commit()
  1067  }
@gopherbot
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@gopherbot gopherbot commented Apr 19, 2014

Comment 1:

CL https://golang.org/cl/89510043 mentions this issue.
@minux
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@minux minux commented Apr 19, 2014

Comment 2:

http://golang.org/pkg/database/sql/#Tx:A transaction must end with a call to Commit or
Rollback.
After a call to Commit or Rollback, all operations on the transaction fail with
ErrTxDone.

Status changed to WorkingAsIntended.

@gopherbot
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@gopherbot gopherbot commented Apr 19, 2014

Comment 3 by Thetawaves:

If the commit fails in the driver, the underlying transaction in the database still
exists. In Sqlite, you can not start a new transaction while one is already in progress
so this effectively locks out the connection. I suppose you could execute a raw 'COMMIT'
query to close this transaction but I find that idea to be quite silly.
@minux
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@minux minux commented Apr 20, 2014

Comment 4:

what do you mean?
The code as it stands implements what the docs says about Tx, so
this is not a bug. If you still think it's a bug, then you will need to
address any dependencies on this rule before propose a change to
it. In the CL discussion, lib/pq is said to depend on this assumption
already, so it's very unlikely we want to change the behavior and
break existing drivers.
@alexbrainman
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@alexbrainman alexbrainman commented Apr 21, 2014

Comment 5:

Thetawaves,
Please provide small program to demonstrate "your problem". Tell us what your program
does, and explain why it should behave differently. It is difficult to make a judgement
without clear understanding the problem. Perhaps it is something driver should do. You
need to convince everyone here that database/sql has to change. Thank you.
Alex
@golang golang locked and limited conversation to collaborators Jun 25, 2016
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