Tag: psql

Waiting for PostgreSQL 17 – Allow \watch queries to stop on minimum rows returned

On 29th of August 2023, Daniel Gustafsson committed patch:

Allow \watch queries to stop on minimum rows returned
 
When running a repeat query with \watch in psql, it can be
helpful to be able to stop the watch process when the query
no longer returns the expected amount of rows.  An example
would be to watch for the presence of a certain event in
pg_stat_activity and stopping when the event is no longer
present, or to watch an index creation and stop when the
index is created.
 
This adds a min_rows=MIN parameter to \watch which can be
set to a non-negative integer, and the watch query will
stop executing when it returns less than MIN rows.
 
Author: Greg Sabino Mullane <htamfids@gmail.com>
Reviewed-by: Michael Paquier <michael@paquier.xyz>
Reviewed-by: Daniel Gustafsson <daniel@yesql.se>
Discussion: https://postgr.es/m/CAKAnmmKStATuddYxP71L+p0DHtp9Rvjze3XRoy0Dyw67VQ45UA@mail.gmail.com

Continue reading Waiting for PostgreSQL 17 – Allow \watch queries to stop on minimum rows returned

How to get advisory lock in shell?

Recently we had interesting problem. There are some maintenance tools, that do stuff that touch database. One can be calling repack, another can be specific dump, and yet another can be applying migrations from application.

The problem is that they can step over each other toes, and cause issues.

So we needed to add some way to prevent them from running at the same time…

Continue reading How to get advisory lock in shell?

A tale of making company-wide standard psqlrc

At a company we have literally thousands of Pg servers. The layout is also kinda non-obvious. Each database is named the same, but contains different data. And in front of it all, we have pgbouncers.

After some talk, it was suggested that perhaps we could make psql prompt show which database it is connected to. And perhaps some more information, like backend pid. I thought it will be simple…

Continue reading A tale of making company-wide standard psqlrc

Waiting for PostgreSQL 13 – psql: Display stats target of extended statistics

On 11st of September 2020, Alvaro Herrera committed patch:

psql: Display stats target of extended statistics
 
The stats target can be set since commit d06215d03, but wasn't shown by
psql.
 
Author: Justin Pryzby <justin@telsasoft.com>
Discussion: https://postgr.es/m/20200831050047.GG5450@telsasoft.com
Reviewed-by: Georgios Kokolatos <gkokolatos@protonmail.com>
Reviewed-by: Tatsuro Yamada <tatsuro.yamada.tf@nttcom.co.jp>

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Changes on explain.depesz.com

I just released new version of Pg::Explain Perl library that is handling parsing of plans for explain.depesz.com.

There are quite a lot of changes, but mostly internal, but one thing is pretty interesting – Pg::Explain, and because of this also explain.depesz.com should be able to parse plans with arbitrary values of border, linestyle, format, unicode_border_linestyle, unicode_column_linestyle, and unicode_header_linestyle psql options.

You can see five simple examples already uploaded:
Continue reading Changes on explain.depesz.com

Waiting for PostgreSQL 13 – Add %x to default PROMPT1 and PROMPT2 in psql

On 12nd of February 2020, Michael Paquier committed patch:

Add %x to default PROMPT1 and PROMPT2 in psql
 
%d can be used to track if the current connection is in a transaction
block or not, and adding it by default to the prompt has the advantage
to not need a modification of .psqlrc, something not possible depending
on the environment.
 
This discussion has happened across various sources, and there was a
strong consensus in favor of this change.
 
Author: Vik Fearing
Reviewed-by: Fabien Coelho
Discussion: https://postgr.es/m/09502c40-cfe1-bb29-10f9-4b3fa7b2bbb2@2ndquadrant.com

Continue reading Waiting for PostgreSQL 13 – Add %x to default PROMPT1 and PROMPT2 in psql

Waiting for PostgreSQL 13 – Allow invisible PROMPT2 in psql.

On 19th of November 2019, Thomas Munro committed patch:

Allow invisible PROMPT2 in psql. 
 
Keep track of the visible width of PROMPT1, and provide %w as a way
for PROMPT2 to generate the same number of spaces.
 
Author: Thomas Munro, with ideas from others
 
Discussion: https://postgr.es/m/CA%2BhUKG%2BzGd7RigjWbxwhzGW59gUpf76ydQECeGdEdodH6nd__A%40mail.gmail.com

Continue reading Waiting for PostgreSQL 13 – Allow invisible PROMPT2 in psql.