Amazing. Awesome. Well, but what is it? We could store json data in Pg since PostgreSQL 9.2 – so it's been there for over 12 years now. How is the new shiny thing different? What does it allow you to do?
Let's see if I can shed some light on it…
Continue reading SQL/JSON is here! (kinda “Waiting for Pg 17")
This question was asked at least twice on some support channel. Getting a row is trivial: select * from table where id = ?. But what about dependencies – the rows that this exported row references?
Decided to take a look at this task.
Continue reading How to get a row, and all of it's dependencies?
Back in March and April I wrote couple of blogposts about upcoming new great feature – full SQL/JSON.
Unfortunately, as of today SQL/JSON has been reverted (removed from sources), both from development version 16, but also from “almost ready" version 15.
There is lengthy discussion about it which you can definitely read if you're so inclined (side note, I didn't catch it immediately, so for future me – RMT is Release Management Team.
Obviously the feature will make its comeback. Whether it will be in 16 or later – can't tell now, but it will definitely reappear.
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
Continue reading Waiting for PostgreSQL 15 – Documentation for SQL/JSON features
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
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
On 28th of March 2022, Andrew Dunstan
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
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
On 17th of January 2022, Michael Paquier committed patch:
Introduce log_destination=jsonlog "jsonlog" is a new value that can be added to log_destination to provide logs in the JSON format, with its output written to a file, making it the third type of destination of this kind, after "stderr" and "csvlog". The format is convenient to feed logs to other applications. There is also a plugin external to core that provided this feature using the hook in elog.c, but this had to overwrite the output of "stderr" to work, so being able to do both at the same time was not possible. The files generated by this log format are suffixed with ".json", and use the same rotation policies as the other two formats depending on the backend configuration. This takes advantage of the refactoring work done previously in ac7c807, bed6ed3, 8b76f89 and 2d77d83 for the backend parts, and 72b76f7 for the TAP tests, making the addition of any new file-based format rather straight-forward. The documentation is updated to list all the keys and the values that can exist in this new format. pg_current_logfile() also required a refresh for the new option. Author: Sehrope Sarkuni, Michael Paquier Reviewed-by: Nathan Bossart, Justin Pryzby Discussion: https://postgr.es/m/CAH7T-aqswBM6JWe4pDehi1uOiufqe06DJWaU5=X7dDLyqUExHg@mail.gmail.com
Continue reading Waiting for PostgreSQL 15 – Introduce log_destination=jsonlog
Every so often, on irc, someone asks how to get value from column that is passed as argument.
This is generally seen as not possible, as pl/PgSQL doesn't have support for dynamic column names.
We can work around it, though. Are the workarounds usable, in terms of performance?
Continue reading Getting value from dynamic column in pl/PgSQL triggers?