Waiting for PostgreSQL 15 – Documentation for SQL/JSON features

On 8th of April 2022, Andrew Dunstan committed patch:

Documentation for SQL/JSON features
 
This documents the features added in commits f79b803dcc, f4fb45d15c,
33a377608f, 1a36bc9dba, 606948b058, 49082c2cc3, 4e34747c88, and
fadb48b00e.
 
I have cleaned up the aggregate section of the submitted docs, but there
is still a deal of copy editing required. However, I thought it best to
have some documentation sooner rather than later so testers can have a
better idea what they are playing with.
 
Nikita Glukhov
 
Reviewers have included (in no particular order) Andres Freund, Alexander
Korotkov, Pavel Stehule, Andrew Alsup, Erik Rijkers, Zhihong Yu,
Himanshu Upadhyaya, Daniel Gustafsson, Justin Pryzby.
 
Discussion: https://postgr.es/m/cd0bb935-0158-78a7-08b5-904886deac4b@postgrespro.ru
Discussion: https://postgr.es/m/7e2cb85d-24cf-4abb-30a5-1a33715959bd@postgrespro.ru

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Waiting for PostgreSQL 15 – JSON_TABLE

On 4th of April 2022, Andrew Dunstan committed patch:

JSON_TABLE
 
This feature allows jsonb data to be treated as a table and thus used in
a FROM clause like other tabular data. Data can be selected from the
jsonb using jsonpath expressions, and hoisted out of nested structures
in the jsonb to form multiple rows, more or less like an outer join.
 
Nikita Glukhov
 
Reviewers have included (in no particular order) Andres Freund, Alexander
Korotkov, Pavel Stehule, Andrew Alsup, Erik Rijkers, Zhihong Yu (whose
name I previously misspelled), Himanshu Upadhyaya, Daniel Gustafsson,
Justin Pryzby.
 
Discussion: https://postgr.es/m/7e2cb85d-24cf-4abb-30a5-1a33715959bd@postgrespro.ru

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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

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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

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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

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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

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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

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Waiting for PostgreSQL 15 – Allow archiving via loadable modules.

On 3rd of February 2022, Robert Haas committed patch:

Allow archiving via loadable modules.
 
Running a shell command for each file to be archived has a lot of
overhead and may not offer as much error checking as you want, or the
exact semantics that you want. So, offer the option to call a loadable
module for each file to be archived, rather than running a shell command.
 
Also, add a 'basic_archive' contrib module as an example implementation
that archives to a local directory.
 
Nathan Bossart, with a little bit of kibitzing by me.
 
Discussion: http://postgr.es/m/20220202224433.GA1036711@nathanxps13

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Waiting for PostgreSQL 15 – Add UNIQUE null treatment option

On 3rd of February 2022, Peter Eisentraut committed patch:

Add UNIQUE null treatment option 
 
The SQL standard has been ambiguous about whether null values in
unique constraints should be considered equal or not.  Different
implementations have different behaviors.  In the SQL:202x draft, this
has been formalized by making this implementation-defined and adding
an option on unique constraint definitions UNIQUE [ NULLS [NOT]
DISTINCT ] to choose a behavior explicitly.
 
This patch adds this option to PostgreSQL.  The default behavior
remains UNIQUE NULLS DISTINCT.  Making this happen in the btree code
is pretty easy; most of the patch is just to carry the flag around to
all the places that need it.
 
The CREATE UNIQUE INDEX syntax extension is not from the standard,
it's my own invention.
 
I named all the internal flags, catalog columns, etc. in the negative
("nulls not distinct") so that the default PostgreSQL behavior is the
default if the flag is false.
 
Reviewed-by: Maxim Orlov <orlovmg@gmail.com>
Reviewed-by: Pavel Borisov <pashkin.elfe@gmail.com>
Discussion: https://www.postgresql.org/message-id/flat/84e5ee1b-387e-9a54-c326-9082674bde78@enterprisedb.com

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Waiting for PostgreSQL 15 – Add HEADER support to COPY text format

On 28th of January 2022, Peter Eisentraut committed patch:

Add HEADER support to COPY text format 
 
The COPY CSV format supports the HEADER option to output a header
line.  This patch adds the same option to the default text format.  On
input, the HEADER option causes the first line to be skipped, same as
with CSV.
 
Author: Rémi Lapeyre <remi.lapeyre@lenstra.fr>
Discussion: https://www.postgresql.org/message-id/flat/CAF1-J-0PtCWMeLtswwGV2M70U26n4g33gpe1rcKQqe6wVQDrFA@mail.gmail.com

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