Re: ORDER BY in materialized view example?

[Jonathan S. Katz]

On 11/23/21 12:44 PM, Tom Lane wrote:

Peter Eisentraut <peter.eisentr...@enterprisedb.com> writes:

On 23.11.21 07:18, Maciek Sakrejda wrote:

An example in the materialized view documentation [1] includes an ORDER
BY clause without a clear reason. Does it help build the index more
efficiently? I suppose it's also sort of like a CLUSTER?

I agree the ORDER BY is not relevant to the example.  There might be
some implementation-dependent advantage to ordering a materialized view,
but if there is, it isn't explained in the example.

Yeah.  It would result in the initial contents of the matview being
ordered, but I'm sure we don't wish to guarantee that REFRESH would
preserve that.  I'm on board with just removing the ORDER BY from
that example.

+1

I'd rather say something like

     If there is an ORDER BY clause in the matview's defining query,
     the original contents of the matview will be ordered that way;
     but REFRESH MATERIALIZED VIEW does not guarantee to preserve
     that ordering.

Thanks,

Jonathan

+1. I think I got bit by this in the real world years back. The above comment is pretty clear.

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