Re: Proposal: Global Index

Robert Haas <robertmhaas(at)gmail(dot)com> writes:
> On Wed, Oct 30, 2019 at 10:13 AM Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>> I believe that the current design of partitioning is explicitly intended
>> to avoid the need for such a construct. It'd be absolutely disastrous
>> to have such a thing from many standpoints, including the breadth of
>> locking needed to work with the global index, the difficulty of vacuuming,
>> and the impossibility of cheaply attaching or detaching partitions.
>> In other words, this is a "feature" we do not want.

> I don't think that's true. Certainly, a lot of EnterpriseDB customers
> want this feature - it comes up regularly in discussions here. But
> that is not to say that the technical challenges are not formidable,
> and I don't think this proposal really grapples with any of them.
> However, that doesn't mean that the feature isn't desirable.

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.

No, I don't have an idea how we might support, eg, uniqueness of
non-partition-key columns without that. But we need to spend our
effort on figuring that out, not on building a complicated mechanism
whose performance is never going to not suck.

regards, tom lane