Re: proposal: schema variables

Nico Williams <nico@cryptonector.com>

From: Nico Williams <nico@cryptonector.com>

To: Tom Lane <tgl@sss.pgh.pa.us>

Cc: Robert Haas <robertmhaas@gmail.com>, Pavel Stehule <pavel.stehule@gmail.com>, PostgreSQL Hackers <pgsql-hackers@postgresql.org>

Date: 2017-11-02T18:52:39Z

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 Thu, Nov 02, 2017 at 11:48:44AM -0400, Tom Lane wrote:
> Nico Williams <nico@cryptonector.com> writes:
> > With access controls, GUCs could become schema variables, and settings
> > from postgresql.conf could move into the database itself (which I think
> > would be nice).
> 
> People re-propose some variant of that every so often, but it never works,
> because it ignores the fact that some of the GUCs' values are needed
> before you can access system catalogs at all, or in places where relying
> on system catalog access would be a bad idea.

ISTM that it should be possible to break the chicken-egg issue by having
the config variables stored in such a way that knowing only the pgdata
directory path should suffice to find them.  That's effectively the case
already in that postgresql.conf is found... there.

One could do probably this as a PoC entirely as a SQL-coded VIEW that
reads and writes (via the adminpack module's pg_catalog.pg_file_write())
postgresql.conf (without preserving comments, or with some rules
regarding comments so that they are effectively attached to params).

Nico
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