Re: Inconsistence in transaction isolation docs

Nico Sabbi wrote:
> /From:
> http://www.postgresql.org/docs/8.2/interactive/transaction-iso.html
>
> "
> Read Committed/ [...]
>
> to me the above sentence sounds inconsistent: it's
> asserting that both 1) and 2) apply:
>
> 1) it never sees ... changes committed during query
> execution by concurrent transactions
>
> 2) Notice that two successive SELECT commands can see
> different data, even though they are within a single
> transaction, if other transactions commit changes
> during execution of the first SELECT
>
> Can anyone explain, please?

1) means: as long as the first SELECT runs ("during
query execution"), you won't see changes made by
another transaction.

2) means: when you run a second SELECT, that SELECT
will see changes made by other transactions, even if
both SELECTs are in one (read commited) transaction.

That doesn't sound contradictory to me.
There is a difference between "during query execution"
and "within a single transaction", maybe that is where
your problem comes from.

Yours,
Laurenz Albe