Re: MVCC and all that... - Mailing list pgsql-general

From Ron Johnson
Subject Re: MVCC and all that...
Date
Msg-id CANzqJaAJ3NN5yv2FY+UBUm4vvz5y46yz=wK6LZaBtOsJ76KusA@mail.gmail.com
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In response to Re: MVCC and all that...  (Justin <zzzzz.graf@gmail.com>)
List pgsql-general
On Tue, Sep 9, 2025 at 8:41 PM Justin <zzzzz.graf@gmail.com> wrote:
[snip] 
Multiple transactions per connection.  I am asking WHY is that a feature.  when one can have multiple sessions, what is the difference?  running multiple transactions in single or multiple sessions means moving  part of transaction logic into the application space. What do we gain here.....
 
If I interpret "Multiple transactions per connection" correctly, they're a great way to emulate WITH HOLD cursors.

For example:
1. In channel #1, open a Read Only cursor.  (Yes, this was long ago.)
2. Fetch a row.
3. Switch to channel #2, begin R/W txn, modify the table, commit.
4. Switch back to channel #1
5. Go to step 2.

Not being an application developer anymore, I've never needed to use WITH HOLD cursors or wish for multiple channels in PG.

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