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>, pgsql-hackers@postgresql.org
Date: 2021-03-25T01:33:06Z
Lists: pgsql-hackers

Attachments

On 3/25/21 1:30 AM, Justin Pryzby wrote:
> On Thu, Mar 25, 2021 at 01:05:37AM +0100, Tomas Vondra wrote:
>> here's an updated patch. 0001 should address most of the today's review
>> items regarding comments etc.
> 
> This is still an issue:
> 
> postgres=# CREATE STATISTICS xt ON a FROM t JOIN t ON true;
> ERROR:  schema "i" does not exist
> 

Ah, right. That's a weird issue. I was really confused about this,
because nothing changes about the grammar or how we check the number of
relations. The problem is pretty trivial - the new code in utility.c
just grabs the first element and casts it to RangeVar, without checking
that it actually is RangeVar. With joins it's a JoinExpr, so we get a
bogus error.

The attached version fixes it by simply doing the check in utility.c.
It's a bit redundant with what's in CreateStatistics() but I don't think
we can just postpone it easily - we need to do the transformation here,
with access to queryString. But maybe we don't need to pass the relid,
when we have the list of relations in CreateStatsStmt itself ...

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