[Pypgsql-devel] [ pypgsql-Feature Requests-1503756 ] SAVEPOINT needs to be done through a Connection method

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Feature Requests item #1503756, was opened at 2006-06-09 15:33
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Category: None
Group: None
Status: Open
Priority: 5
Submitted By: Clarence (clarence1126)
Assigned to: Nobody/Anonymous (nobody)
Summary: SAVEPOINT needs to be done through a Connection method

Initial Comment:
My application has the following outline:
  1) Delete all data for a given hour
  2) Do many inserts to update the data for that hour
Any of those inserts might fail due to referential 
integrity violations, and that is acceptable. However, 
any such error invalidates the transaction. The current 
code actually does
  1) Delete all data for a given hour
  1a) Commit
  2) Insert new data (1 tuple) for the hour
  2a) Commit
  2c) go to 2
This of course causes the data for that hour to be read 
as either zero or any value up to the the correct 
value.

So I want to use savepoints instead. But I cannot use 
them through a cursor, for the same reason that one 
cannot do commits/rollbacks through a cursor, namely 
that the Connection object wants to know about the 
state, hence it provides the commit and rollback 
methods.

The Connection object needs to know about savepoints 
because currently, if any query gets an error, the 
Connection object issues a ROLLBACK. If the user has 
previously set a savepoint via a query, the Connection 
doesn't know that and the user's work is not saved.

So I would suggest some kind of savepoint access be 
added to the Connection. I don't think it necessarily 
needs to be as baroque as allowed by the SQL standard, 
in particular multiple savepoints outstanding, etc. In 
fact, I'll probably make a local modification which 
will consist of just a savepoint() and release() 
method, taking no arguments, just to get my problem 
solved. More than that may not be necessary (given that 
nobody has apparently ever even run into the problem 
before).

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