The manual still seems to offer just such a guarantee here:
https://www.postgresql.org/docs/current/sql-select.html#SQL-UNION
> Multiple UNION operators in the same SELECT statement are evaluated left
to right, unless otherwise indicated by parentheses.
In the case of UNION ALL, is this supposed
>> No, there is no guarantee. It's just that UNION ALL works this way today
>> (preserving the order of the subselects) - and I'm not even sure about
>> that, it may not preserve the order in all cases, with different indexes
or
>> partitioning or a parallel plan, etc.
>
> Yeah, that. You can get
On Thursday, July 14, 2022, Shay Rojansky wrote:
>
> If there's a guarantee that UNION ALL preserves ordering - as Tom seems to
> indicate in the thread quoted above - then the above works. If there's no
> such guarantee, then AFAIK the above can't be rewritten; putting the ORDER
> BY outside - o
Pantelis Theodosiou writes:
> On Thu, Jul 14, 2022 at 9:16 AM Shay Rojansky wrote:
>> I was trying to understand what - if any - are the guarantees with
>> regards to ordering for combining queries (UNION/UNION ALL/...).
> No, there is no guarantee. It's just that UNION ALL works this way today
On Thu, Jul 14, 2022 at 9:16 AM Shay Rojansky wrote:
>
> >> I was trying to understand what - if any - are the guarantees with
> regards to ordering for combining queries (UNION/UNION ALL/...). From this
> message[1], it seems that UNION ALL does preserve the ordering of the
> operand queries, wh
>> I was trying to understand what - if any - are the guarantees with
regards to ordering for combining queries (UNION/UNION ALL/...). From this
message[1], it seems that UNION ALL does preserve the ordering of the
operand queries, whereas UNION does not (presumably neither do INTERSECT,
INTERSECT
On Wed, Jul 13, 2022 at 5:08 PM Shay Rojansky wrote:
> Greetings.
>
> I was trying to understand what - if any - are the guarantees with regards
> to ordering for combining queries (UNION/UNION ALL/...). From this
> message[1], it seems that UNION ALL does preserve the ordering of the
> operand q
Greetings.
I was trying to understand what - if any - are the guarantees with regards
to ordering for combining queries (UNION/UNION ALL/...). From this
message[1], it seems that UNION ALL does preserve the ordering of the
operand queries, whereas UNION does not (presumably neither do INTERSECT,
I
