| From: | Peter Geoghegan <pg(at)bowt(dot)ie> |
|---|---|
| To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
| Cc: | Andrew Dunstan <andrew(dot)dunstan(at)2ndquadrant(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Invisible Indexes |
| Date: | 2018-06-18 22:16:38 |
| Message-ID: | CAH2-Wz=ZFd5LLJekX3Q7zLnBERv+DRwLR0zLD8B_QArKeXLBSg@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Mon, Jun 18, 2018 at 3:12 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> Perhaps there are use-cases where you want globally visible effects,
> but the primary use-case Andrew cited (i.e. EXPLAIN experimentation)
> would not want that.
>
> Anyway, if we do it with a GUC, the user can control the scope of
> the effects.
I had imagined that those use cases would be the most common. Dropping
an index in production because it very much looks like it is unused is
always a bit nerve-wracking in my experience. It's often hard to be
100% sure due to factors like replicas, the possible loss of statistic
collector stats masking a problem, the possibility that there are very
important queries that do use the index but are only run very
infrequently, and so on.
--
Peter Geoghegan
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