Re: On partitioning

Hi,

> From: Jim Nasby [mailto:Jim(dot)Nasby(at)BlueTreble(dot)com]
> On 12/2/14, 9:43 PM, Amit Langote wrote:
>
> >> >What are you going to do if the partitioning key has two columns of
> >> >different data types?
> >> >
> > Sorry, this totally eluded me. Perhaps, the 'values' needs some more thought.
> They are one of the most crucial elements of the scheme.
> >
> > I wonder if your suggestion of pg_node_tree plays well here. This then could
> be a list of CONSTs or some such... And I am thinking it's a concern only for
> range partitions, no? (that is, a multicolumn partition key)
> >
> > I think partkind switches the interpretation of the field as appropriate. Am I
> missing something? By the way, I had mentioned we could have two values
> fields each for range and list partition kind.
>
> The more SQL way would be records (composite types). That would make
> catalog inspection a LOT easier and presumably make it easier to change the
> partitioning key (I'm assuming ALTER TYPE cascades to stored data). Records
> are stored internally as tuples; not sure if that would be faster than a List of
> Consts or a pg_node_tree. Nodes would theoretically allow using things other
> than Consts, but I suspect that would be a bad idea.
>

While I couldn’t find an example in system catalogs where a record/composite type is used, there are instances of pg_node_tree at a number of places like in pg_attrdef and others. Could you please point me to such a usage for reference?

> Something else to consider... our user-space support for ranges is now
> rangetypes, so perhaps that's what we should use for range partitioning. The
> up-side (which would be a double-edged sword) is that you could leave holes
> in your partitioning map. Note that in the multi-key case we could still have a
> record of rangetypes.

That is something I had mind at least at some point. My general doubt remains about the usage of user space SQL types for catalog fields though I may be completely uninitiated about such usage.

Thanks,
Amit