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

Continue reading Waiting for PostgreSQL 15 – Documentation for SQL/JSON features

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

Continue reading Waiting for PostgreSQL 15 – JSON_TABLE

DBA tips ‘n tricks – search in every field in a table

Sometimes you just want to find some value, regardless of which column it's in. If the table has few columns you can easily:

=$ SELECT * FROM TABLE WHERE a ~ '...' OR b ~ '...' OR c ~ '...'

But if there are many columns writing such query quickly becomes tedious. Luckily there is simple solution.

Continue reading DBA tips ‘n tricks – search in every field in a table

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