Horton

Re: PoC/WIP: Extended statistics on expressions

Dean Rasheed <dean.a.rasheed@gmail.com>

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From: Dean Rasheed <dean.a.rasheed@gmail.com>
To: Justin Pryzby <pryzby@telsasoft.com>
Cc: Tomas Vondra <tomas.vondra@enterprisedb.com>, PostgreSQL Hackers <pgsql-hackers@postgresql.org>
Date: 2021-01-22T09:00:40Z
Lists: pgsql-hackers 
On Fri, 22 Jan 2021 at 04:46, Justin Pryzby <pryzby@telsasoft.com> wrote:
>
> I think you'll maybe have to do something better - this seems a bit too weird:
>
> | postgres=# CREATE STATISTICS s2 ON (i+1) ,i FROM t;
> | postgres=# \d t
> | ...
> |     "public"."s2" (ndistinct, dependencies, mcv) ON i FROM t
>

I guess that's not surprising, given that old psql knows nothing about
expressions in stats.

In general, I think connecting old versions of psql to newer servers
is not supported. You're lucky if \d works at all. So it shouldn't be
this patch's responsibility to make that output nicer.

Regards,
Dean

Commits

  1. Disallow extended statistics on system columns

  2. Identify simple column references in extended statistics

  3. Don't print extra parens around expressions in extended stats

  4. Change position of field "transformed" in struct CreateStatsStmt.

  5. Add transformed flag to nodes/*funcs.c for CREATE STATISTICS

  6. Stabilize stats_ext test with other collations

  7. Extended statistics on expressions

  8. Reduce duration of stats_ext regression tests

  9. Allow composite types in catalog bootstrap

  10. Convert Typ from array to list in bootstrap

  11. Disallow CREATE STATISTICS on system catalogs