Re: Should we warn against using too many partitions?

On Fri, Jun 07, 2019 at 06:46:59AM +1200, David Rowley wrote:
> On Thu, 6 Jun 2019 at 17:29, Justin Pryzby <pryzby@telsasoft.com> wrote:
> > >+
> > >+  <sect2 id="ddl-partitioning-declarative-best-practices">
> > >+   <title>Declarative Partitioning Best Practices</title>
> > >+
> > >+   <para>
> > >+    The choice of how to partition a table should be considered carefully as
> >
> > Either say "How to partition consider should be .." or "The choice should MADE carefully" ?
> 
> I've changed "considered" to "made". I'm unable to make sense of the
> first suggestion there :(

The first option was intended to be:
|How to partition a table should be considered carefully.

(The idea being that the "choice" doesn't need to be considered carefully but
the thing itself).

> > >+    critical decision to make.  Not having enough partitions may mean that
> > >+    indexes remain too large and that data locality remains poor which could
> > >+    result in poor cache hit ratios.  However, dividing the table into too
> > >+    many partitions can also cause issues.  Too many partitions can mean
> > >+    slower query planning times and higher memory consumption during both
> > >+    query planning and execution.  It's also important to consider what
> > >+    changes may occur in the future when choosing how to partition your table.
> > >+    For example, if you choose to have one partition per customer and you
> > >+    currently have a small number of large customers, what will the
> >
> > have ONLY ?
> 
> I assume you mean after the "have" before "one partition per
> customer"?

No, I meant "currently have ONLY".

> I don't quite understand that since in the scenario we're
> partitioning by customer, so it's not possible to have more than one
> partition per customer, only the reverse is possible. It seems to me
> injecting "only" there would just confuse things.

Thanks,
Justin