This might not interest many of you, but I recently heard about at least two people that stumbled upon the problems I did, so I figured I can write about problems we discovered, and how we solved them (or not).
When we began our journey, the latest Pg was 14.x, that's why we're upgrading to 14, not 15. But I suspect upgrading to 15 wouldn't change much …
Continue reading A tale about (incomplete) upgrade from PostgreSQL 12 to 14
psql, the database client for PostgreSQL has, since forever, support for variables.
These let you write certain queries in a way that is safe even when getting params from “outside".
Let's see what can be done with it…
Continue reading Variables in psql, how to use them?
On 7th of April 2023, Tom Lane committed patch:
Add array_sample() and array_shuffle() functions.
These are useful in Monte Carlo applications.
Martin Kalcher, reviewed/adjusted by Daniel Gustafsson and myself
Continue reading Waiting for PostgreSQL 16 – Add array_sample() and array_shuffle() functions.
Not everyone knows, but at since PostgreSQL 9.6, we have some built-in roles.
Of course, there is always superuser (usually called postgres), but I'm not talking about it. I'm talking about magical roles that have names starting with pg_.
Continue reading System roles – what, why, how?
On 11st of February 2023, Andres Freund committed patch:
Add pg_stat_io view, providing more detailed IO statistics
Builds on 28e626bde00 and f30d62c2fc6. See the former for motivation.
Rows of the view show IO operations for a particular backend type, IO target
object, IO context combination (e.g. a client backend's operations on
permanent relations in shared buffers) and each column in the view is the
total number of IO Operations done (e.g. writes). So a cell in the view would
be, for example, the number of blocks of relation data written from shared
buffers by client backends since the last stats reset.
In anticipation of tracking WAL IO and non-block-oriented IO (such as
temporary file IO), the "op_bytes" column specifies the unit of the "reads",
"writes", and "extends" columns for a given row.
Rows for combinations of IO operation, backend type, target object and context
that never occur, are ommitted entirely. For example, checkpointer will never
operate on temporary relations.
Similarly, if an IO operation never occurs for such a combination, the IO
operation's cell will be null, to distinguish from 0 observed IO
operations. For example, bgwriter should not perform reads.
Note that some of the cells in the view are redundant with fields in
pg_stat_bgwriter (e.g. buffers_backend). For now, these have been kept for
Author: Melanie Plageman <firstname.lastname@example.org>
Author: Samay Sharma <email@example.com>
Reviewed-by: Maciek Sakrejda <firstname.lastname@example.org>
Reviewed-by: Lukas Fittl <email@example.com>
Reviewed-by: Andres Freund <firstname.lastname@example.org>
Reviewed-by: Justin Pryzby <email@example.com>
Continue reading Waiting for PostgreSQL 16 – Add pg_stat_io view, providing more detailed IO statistics
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?
Whenever people look for help with queries, one of the first things that I ask is: what is \d of the table.
Which works great, with the caveat, that the person on the other end must be somewhat familiar with psql. And quite often it's not the case.
So I figured, I can try to fix it.
Continue reading Now you can \d table not only in psql 🙂
Well, the short answer is: NEVER. But given how often I see people ask about it, I'll try to expand my answer a bit…
Continue reading When to use VACUUM FULL
On 4th of February 2023, Dean Rasheed committed patch:
Allow underscores in integer and numeric constants.
This allows underscores to be used in integer and numeric literals,
and their corresponding type input functions, for visual grouping.
A single underscore is allowed between any 2 digits, or immediately
after the base prefix indicator of non-decimal integers, per SQL:202x
Peter Eisentraut and Dean Rasheed
Continue reading Waiting for PostgreSQL 16 – Allow underscores in integer and numeric constants.
FZF is quite popular tool for fuzzy string finder. Very helpful for checking history of commands.
But, can I use it in psql?
Continue reading Can you use fzf for psql history?