Re: [HACKERS] proposal: schema variables

Pavel Stehule <pavel.stehule@gmail.com>

From: Pavel Stehule <pavel.stehule@gmail.com>

To: Pavel Luzanov <p.luzanov@postgrespro.ru>

Cc: "David G. Johnston" <david.g.johnston@gmail.com>, Pavel Golub <pavel@gf.microolap.com>, PostgreSQL Hackers <pgsql-hackers@postgresql.org>

Date: 2018-03-20T17:38:47Z

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

Attachments

schema-variables-poc-180320-01-diff (application/octet-stream)
schema_variables.out (application/octet-stream)

Hi

I am sending new update. The code is less ugly, and the current
functionality is +/- final for first stage. It should be good enough for
playing and testing this concept.

What is supported:

1. scalar, composite and array variables
2. composite can be defined on place or some composite type can be used
3. variable, or any field of variable, can have defined default value
4. variable is database object - the access rights are required
5. the values are stored in binary form with defined typmod

An usage is very simple:

postgres=# create variable foo as numeric default 0;
CREATE VARIABLE
postgres=# select foo;
┌─────┐
│ foo │
╞═════╡
│   0 │
└─────┘
(1 row)

postgres=# let foo = pi();
LET
postgres=# select foo;
┌──────────────────┐
│       foo        │
╞══════════════════╡
│ 3.14159265358979 │
└──────────────────┘
(1 row)

postgres=# create variable boo as (x numeric default 0, y numeric default
0);
CREATE VARIABLE
postgres=# let boo.x = 100;
LET
postgres=# select boo;
┌─────────┐
│   boo   │
╞═════════╡
│ (100,0) │
└─────────┘
(1 row)

postgres=# select boo.x;
┌─────┐
│  x  │
╞═════╡
│ 100 │
└─────┘
(1 row)

Please try it.

Regards

Pavel