Re: [HACKERS] proposal: schema variables

Peter Eisentraut <peter.eisentraut@2ndquadrant.com>

From: Peter Eisentraut <peter.eisentraut@2ndquadrant.com>

To: Pavel Stehule <pavel.stehule@gmail.com>, Robert Haas <robertmhaas@gmail.com>

Cc: Arthur Zakirov <a.zakirov@postgrespro.ru>, PostgreSQL Hackers <pgsql-hackers@postgresql.org>

Date: 2018-05-01T01:56:45Z

Lists: pgsql-hackers, pgsql-performance

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

Move WAL sequence code into its own file
- a87987cafca6 19 (unreleased) cited
Add ExplainState argument to pg_plan_query() and planner().
- c83ac02ec730 19 (unreleased) cited
Don't include access/htup_details.h in executor/tuptable.h
- 1a8b5b11e48a 19 (unreleased) cited
Refactor to avoid code duplication in transformPLAssignStmt.
- b0fb2c6aa5a4 19 (unreleased) cited
Avoid including commands/dbcommands.h in so many places
- 325fc0ab14d1 19 (unreleased) cited
Restrict psql meta-commands in plain-text dumps.
- 71ea0d679543 19 (unreleased) cited
Split func.sgml into more manageable pieces
- 4e23c9ef65ac 19 (unreleased) cited
Fix squashing algorithm for query texts
- 0f65f3eec478 18.0 cited
EXPLAIN: Always use two fractional digits for row counts.
- 95dbd827f2ed 18.0 cited
Preliminary refactoring of plpgsql expression construction.
- a654af21ae52 18.0 cited
plpgsql: pure parser and reentrant scanner
- 7b27f5fd36cb 18.0 cited
Add some sanity checks in executor for query ID reporting
- 24f520594809 18.0 cited
Fix misleading error message context
- 4af123ad45bd 18.0 cited
Add macros for looping through a List without a ListCell.
- 14dd0f27d7cd 17.0 cited

On 4/20/18 13:45, Pavel Stehule wrote:
>     I dunno, it seems awfully different to me.  There's only one "column",
>     right?  What code is really shared here?  Are constraints and triggers
>     even desirable feature for variables?  What would be the use case?
> 
> 
> The schema variable can hold composite value. The patch allows to use
> any composite type or adhoc composite values
> 
> DECLARE x AS compositetype;
> DECLARE x AS (a int, b int, c int);

I'm not sure that this anonymous composite type thing is such a good
idea.  Such a variable will then be incompatible with anything else,
because it's of a different type.

In any case, I find that a weak argument for storing this in pg_class.
You could just as well create these pg_class entries implicitly and link
them from "pg_variable", same as composite types have a main entry in
pg_type and additional stuff in pg_class.

>     I think stuffing this into pg_class is pretty strange.
> 
> It will be if variable is just scalar value without any possibilities.
> But then there is only low benefit
> 
> The access rights implementation is shared with other from pg_class too.

In DB2, the privileges for variables are named READ and WRITE.  That
would make more sense to me than reusing the privilege names for tables.

-- 
Peter Eisentraut              http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services