Same transactions across multiple threads

[qizzzh]

I'm using the C++ spanner client and make copies when necessary according to

  * Instances of this class created via copy-construction or copy-assignment
  * share the underlying pool of connections. Access to these copies via multiple
  * threads is guaranteed to work. Two threads operating on the same instance of
  * this class is not guaranteed to work.
  * 

for thread safety. However I didn't find any documentation around whether it's safe to share the same transaction across multiple threads. Can someone confirm whether it's safe or not? Thank you!

[devbww]

Yes, a transaction can be used across multiple threads. It seems there would need to be some synchronization to decide who commits and when, however.