Horton

Re: PoC/WIP: Extended statistics on expressions

Tomas Vondra <tomas.vondra@enterprisedb.com>

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From: Tomas Vondra <tomas.vondra@enterprisedb.com>
To: Justin Pryzby <pryzby@telsasoft.com>
Cc: Dean Rasheed <dean.a.rasheed@gmail.com>, hackers <pgsql-hackers@postgresql.org>
Date: 2021-09-01T19:56:20Z
Lists: pgsql-hackers 

On 9/1/21 9:38 PM, Justin Pryzby wrote:
> On Wed, Sep 01, 2021 at 06:45:29PM +0200, Tomas Vondra wrote:
>>>> Patch 0001 fixes the "double parens" issue discussed elsewhere in this
>>>> thread, and patch 0002 tweaks CREATE STATISTICS to treat "(a)" as a simple
>>>> column reference.
>>>
>>> 0002 refuses to create expressional stats on a simple column reference like
>>> (a), which I think is helps to avoid a user accidentally creating useless ext
>>> stats objects (which are redundant with the table's column stats).
>>>
>>> 0002 does not attempt to refuse cases like (a+0), which I think is fine:
>>> we don't try to reject useless cases if someone insists on it.
>>> See 240971675, 701fd0bbc.
>>>
>>> So I am +1 to apply both patches.
>>>
>>> I added this as an Opened Item for increased visibility.
>>
>> I've pushed both fixes, so the open item should be resolved.
> 
> Thank you - I marked it as such.
> 
> There are some typos in 537ca68db (refenrece)
> I'll add them to my typos branch if you don't want to patch them right now or
> wait to see if someone notices anything else.
> 

Yeah, probably better to wait a bit. Any opinions on rejecting 
expressions referencing system attributes or no attributes at all?

regards

-- 
Tomas Vondra
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company

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