Re: Proposal: Global Index

Peter Geoghegan <pg@bowt.ie> writes:
> On Wed, Oct 30, 2019 at 9:23 AM Tom Lane <tgl@sss.pgh.pa.us> wrote:
>> Well, the *effects* of the feature seem desirable, but that doesn't
>> mean that we want an implementation that actually has a shared index.
>> As soon as you do that, you've thrown away most of the benefits of
>> having a partitioned data structure in the first place.

> Right, but that's only the case for the global index. Global indexes
> are useful when used judiciously.

But ... why bother with partitioning then?  To me, the main reasons
why you might want a partitioned table are

* ability to cheaply add and remove partitions, primarily so that
you can cheaply do things like "delete the oldest month's data".

* ability to scale past our limits on the physical size of one table
--- both the hard BlockNumber-based limit, and the performance
constraints of e.g. vacuuming a very large table.

Both of those go out the window with a global index.  So you might
as well just have one table and forget all the overhead.

            regards, tom lane