Author: depesz

Waiting for PostgreSQL 15 – SQL/JSON query functions

On 29th of March 2022, Andrew Dunstan committed patch:

SQL/JSON query functions
 
This introduces the SQL/JSON functions for querying JSON data using
jsonpath expressions. The functions are:
 
JSON_EXISTS()
JSON_QUERY()
JSON_VALUE()
 
All of these functions only operate on jsonb. The workaround for now is
to cast the argument to jsonb.
 
JSON_EXISTS() tests if the jsonpath expression applied to the jsonb
value yields any values. JSON_VALUE() must return a single value, and an
error occurs if it tries to return multiple values. JSON_QUERY() must
return a json object or array, and there are various WRAPPER options for
handling scalar or multi-value results. Both these functions have
options for handling EMPTY and ERROR conditions.
 
Nikita Glukhov
 
Reviewers have included (in no particular order) Andres Freund, Alexander
Korotkov, Pavel Stehule, Andrew Alsup, Erik Rijkers, Zihong Yu,
Himanshu Upadhyaya, Daniel Gustafsson, Justin Pryzby.
 
Discussion: https://postgr.es/m/cd0bb935-0158-78a7-08b5-904886deac4b@postgrespro.ru

Continue reading Waiting for PostgreSQL 15 – SQL/JSON query functions

Waiting for PostgreSQL 15 – IS JSON predicate

On 28th of March 2022, Andrew Dunstan
New Blog Post

Title: Waiting for PostgreSQL 15 – IS JSON predicate

On 28th of March 2022, Andrew Dunstan committed patch:

IS JSON predicate
 
This patch intrdocuces the SQL standard IS JSON predicate. It operates
on text and bytea values representing JSON as well as on the json and
jsonb types. Each test has an IS and IS NOT variant. The tests are:
 
IS JSON [VALUE]
IS JSON ARRAY
IS JSON OBJECT
IS JSON SCALAR
IS JSON  WITH | WITHOUT UNIQUE KEYS
 
These are mostly self-explanatory, but note that IS JSON WITHOUT UNIQUE
KEYS is true whenever IS JSON is true, and IS JSON WITH UNIQUE KEYS is
true whenever IS JSON is true except it IS JSON OBJECT is true and there
are duplicate keys (which is never the case when applied to jsonb values).
 
Nikita Glukhov
 
Reviewers have included (in no particular order) Andres Freund, Alexander
Korotkov, Pavel Stehule, Andrew Alsup, Erik Rijkers, Zihong Yu,
Himanshu Upadhyaya, Daniel Gustafsson, Justin Pryzby.
 
Discussion: https://postgr.es/m/cd0bb935-0158-78a7-08b5-904886deac4b@postgrespro.ru

Continue reading Waiting for PostgreSQL 15 – IS JSON predicate

Waiting for PostgreSQL 15 – SQL/JSON constructors

On 27th of March 2022, Andrew Dunstan committed patch:

SQL/JSON constructors
 
This patch introduces the SQL/JSON standard constructors for JSON:
 
JSON()
JSON_ARRAY()
JSON_ARRAYAGG()
JSON_OBJECT()
JSON_OBJECTAGG()
 
For the most part these functions provide facilities that mimic
existing json/jsonb functions. However, they also offer some useful
additional functionality. In addition to text input, the JSON() function
accepts bytea input, which it will decode and constuct a json value from.
The other functions provide useful options for handling duplicate keys
and null values.
 
This series of patches will be followed by a consolidated documentation
patch.
 
Nikita Glukhov
 
Reviewers have included (in no particular order) Andres Freund, Alexander
Korotkov, Pavel Stehule, Andrew Alsup, Erik Rijkers, Zihong Yu,
Himanshu Upadhyaya, Daniel Gustafsson, Justin Pryzby.
 
Discussion: https://postgr.es/m/cd0bb935-0158-78a7-08b5-904886deac4b@postgrespro.ru

Continue reading Waiting for PostgreSQL 15 – SQL/JSON constructors

Waiting for PostgreSQL 15 – Add support for MERGE SQL command

On 28th of March 2022, Alvaro Herrera committed patch:

Add support for MERGE SQL command
 
MERGE performs actions that modify rows in the target table using a
source table or query. MERGE provides a single SQL statement that can
conditionally INSERT/UPDATE/DELETE rows -- a task that would otherwise
require multiple PL statements.  For example,
 
MERGE INTO target AS t
USING source AS s
ON t.tid = s.sid
WHEN MATCHED AND t.balance > s.delta THEN
  UPDATE SET balance = t.balance - s.delta
WHEN MATCHED THEN
  DELETE
WHEN NOT MATCHED AND s.delta > 0 THEN
  INSERT VALUES (s.sid, s.delta)
WHEN NOT MATCHED THEN
  DO NOTHING;
 
MERGE works with regular tables, partitioned tables and inheritance
hierarchies, including column and row security enforcement, as well as
support for row and statement triggers and transition tables therein.
 
MERGE is optimized for OLTP and is parameterizable, though also useful
for large scale ETL/ELT. MERGE is not intended to be used in preference
to existing single SQL commands for INSERT, UPDATE or DELETE since there
is some overhead.  MERGE can be used from PL/pgSQL.
 
MERGE does not support targetting updatable views or foreign tables, and
RETURNING clauses are not allowed either.  These limitations are likely
fixable with sufficient effort.  Rewrite rules are also not supported,
but it's not clear that we'd want to support them.
 
Author: Pavan Deolasee <pavan.deolasee@gmail.com>
Author: Álvaro Herrera <alvherre@alvh.no-ip.org>
Author: Amit Langote <amitlangote09@gmail.com>
Author: Simon Riggs <simon.riggs@enterprisedb.com>
Reviewed-by: Peter Eisentraut <peter.eisentraut@enterprisedb.com>
Reviewed-by: Andres Freund <andres@anarazel.de> (earlier versions)
Reviewed-by: Peter Geoghegan <pg@bowt.ie> (earlier versions)
Reviewed-by: Robert Haas <robertmhaas@gmail.com> (earlier versions)
Reviewed-by: Japin Li <japinli@hotmail.com>
Reviewed-by: Justin Pryzby <pryzby@telsasoft.com>
Reviewed-by: Tomas Vondra <tomas.vondra@enterprisedb.com>
Reviewed-by: Zhihong Yu <zyu@yugabyte.com>
Discussion: https://postgr.es/m/CANP8+jKitBSrB7oTgT9CY2i1ObfOt36z0XMraQc+Xrz8QB0nXA@mail.gmail.com
Discussion: https://postgr.es/m/CAH2-WzkJdBuxj9PO=2QaO9-3h3xGbQPZ34kJH=HukRekwM-GZg@mail.gmail.com
Discussion: https://postgr.es/m/20201231134736.GA25392@alvherre.pgsql

Continue reading Waiting for PostgreSQL 15 – Add support for MERGE SQL command

Waiting for PostgreSQL 15 – Add support for security invoker views.

On 22nd of March 2022, Dean Rasheed committed patch:

Add support for security invoker views. 
 
A security invoker view checks permissions for accessing its
underlying base relations using the privileges of the user of the
view, rather than the privileges of the view owner. Additionally, if
any of the base relations are tables with RLS enabled, the policies of
the user of the view are applied, rather than those of the view owner.
 
This allows views to be defined without giving away additional
privileges on the underlying base relations, and matches a similar
feature available in other database systems.
 
It also allows views to operate more naturally with RLS, without
affecting the assignments of policies to users.
 
Christoph Heiss, with some additional hacking by me. Reviewed by
Laurenz Albe and Wolfgang Walther.
 
Discussion: https://postgr.es/m/b66dd6d6-ad3e-c6f2-8b90-47be773da240%40cybertec.at

Continue reading Waiting for PostgreSQL 15 – Add support for security invoker views.

Is my autovacuum configured properly?

Autovacuum was added LONG time ago (in 7.4, as pg_autovacuum). Since then, there were many changes related to it.

These days, hopefully, we no longer see someone saying that they have to disable autovacuum due to performance issues.

But I still see people that say that they have to run daily/weekly vacuum because “autovacuum is not enough". Is it really?

Continue reading Is my autovacuum configured properly?

PGDayPL is coming :)

Following is text provided by organizers. On my end I can say that I'll be there, and I'm on “Talk selection team" 🙂

The first ever Polish PostgreSQL conference is approaching faster than we think.

On April 22, 2022, we invite you to spend the whole day gaining top technical knowledge and broadening your horizons. PGDayPL 2022 is a great gaining opportunity to talk to the amazing speakers and spend time in the accompaniment of what we are most passionate about.

The conference is held at the POLIN Conference Center in Warsaw's Muranów.

What can you expect?

  • fantastic lectures where you will gain technical knowledge – in both Polish and English!
  • panels led by people with a passion for PostgreSQL and IT
  • gifts for all conference attendees and additional bonuses for our speakers
  • delicious catering for guests
  • integration meeting after a successful conference

Learn more: https://pgday.pl/.