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Re: Is replacing transactions with CTE a good idea?

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On Sun, Apr  4, 2021 at 08:35:41AM -0400, Dave Cramer wrote:
> 
> 
> On Thu, 1 Apr 2021 at 15:39, Bruce Momjian <bruce@xxxxxxxxxx> wrote:
> 
>     On Thu, Apr  1, 2021 at 11:24:48AM -0400, Dave Cramer wrote:
>     > CTE's don't change the isolation level. I'm not sure what you are getting
>     at
>     > here ?
> 
>     I think what he/she means here is that all queries in a CTE use a single
>     snapshot, meaning you don't see changes by commits that happen between
>     queries that are part of the same CTE.  If you were running the queries
>     separately in read committed mode, you would see those changes, but you
>     would not see them in repeatable read or serializable transaction mode.
> 
> OK, that makes sense, but I think it is wrong minded to think that this
> absolves one of taking isolation into account.
> 
> When you make the first read you will still have to deal with all of the
> isolation issues 

I have no idea what you are saying above.  Why is a SELECT-only CTE not
the same as a repeatable-read SELECT-only multi-statement transaction? 
Are you saying that a SELECT in a CTE doesn't do SELECT FOR UPDATE?  

-- 
  Bruce Momjian  <bruce@xxxxxxxxxx>        https://momjian.us
  EDB                                      https://enterprisedb.com

  If only the physical world exists, free will is an illusion.






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