Waiting for PostgreSQL 16 – Allow underscores in integer and numeric constants.

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.
For example:
 
    1_500_000_000
    3.14159_26535_89793
    0xffff_ffff
    0b_1001_0001
 
A single underscore is allowed between any 2 digits, or immediately
after the base prefix indicator of non-decimal integers, per SQL:202x
draft.
 
Peter Eisentraut and Dean Rasheed
 
Discussion: https://postgr.es/m/84aae844-dc55-a4be-86d9-4f0fa405cc97%40enterprisedb.com

Continue reading Waiting for PostgreSQL 16 – Allow underscores in integer and numeric constants.

Waiting for PostgreSQL 16 – Invent random_normal() to provide normally-distributed random numbers.

On 9th of January 2023, Tom Lane committed patch:

Invent random_normal() to provide normally-distributed random numbers.
 
There is already a version of this in contrib/tablefunc, but it
seems sufficiently widely useful to justify having it in core.
 
Paul Ramsey
 
Discussion: https://postgr.es/m/CACowWR0DqHAvOKUCNxTrASFkWsDLqKMd6WiXvVvaWg4pV1BMnQ@mail.gmail.com

Continue reading Waiting for PostgreSQL 16 – Invent random_normal() to provide normally-distributed random numbers.

Waiting for PostgreSQL 16 – Non-decimal integer literals

On 14th of December 2022, Peter Eisentraut committed patch:

Non-decimal integer literals 
 
Add support for hexadecimal, octal, and binary integer literals:
 
    0x42F
    0o273
    0b100101
 
per SQL:202x draft.
 
This adds support in the lexer as well as in the integer type input
functions.
 
Reviewed-by: John Naylor <john.naylor@enterprisedb.com>
Reviewed-by: Zhihong Yu <zyu@yugabyte.com>
Reviewed-by: David Rowley <dgrowleyml@gmail.com>
Reviewed-by: Dean Rasheed <dean.a.rasheed@gmail.com>
Discussion: https://www.postgresql.org/message-id/flat/b239564c-cad0-b23e-c57e-166d883cb97d@enterprisedb.com

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Waiting for PostgreSQL 16 – Add grantable MAINTAIN privilege and pg_maintain role.

On 14th of December 2022, Jeff Davis committed patch:

Add grantable MAINTAIN privilege and pg_maintain role.
 
Allows VACUUM, ANALYZE, REINDEX, REFRESH MATERIALIZED VIEW, CLUSTER,
and LOCK TABLE.
 
Effectively reverts 4441fc704d. Instead of creating separate
privileges for VACUUM, ANALYZE, and other maintenance commands, group
them together under a single MAINTAIN privilege.
 
Author: Nathan Bossart
Discussion: https://postgr.es/m/20221212210136.GA449764@nathanxps13
Discussion: https://postgr.es/m/45224.1670476523@sss.pgh.pa.us

Continue reading Waiting for PostgreSQL 16 – Add grantable MAINTAIN privilege and pg_maintain role.

Waiting for PostgreSQL 16 – Add test scaffolding for soft error reporting from input functions.

Title: On 9th of December 2022, Tom Lane committed patch:

Add test scaffolding for soft error reporting from input functions.
 
pg_input_is_valid() returns boolean, while pg_input_error_message()
returns the primary error message if the input is bad, or NULL
if the input is OK.  The main reason for having two functions is
so that we can test both the details-wanted and the no-details-wanted
code paths.
 
Although these are primarily designed with testing in mind,
it could well be that they'll be useful to end users as well.
 
This patch is mostly by me, but it owes very substantial debt to
earlier work by Nikita Glukhov, Andrew Dunstan, and Amul Sul.
Thanks to Andres Freund for review.
 
Discussion: https://postgr.es/m/3bbbb0df-7382-bf87-9737-340ba096e034@postgrespro.ru

Continue reading Waiting for PostgreSQL 16 – Add test scaffolding for soft error reporting from input functions.

Picking random element, with weights

Whenever I'm doing some testing I need sample data. Easiest way to do it is to generate data using some random/generate_series queries.

But what if I need specific frequencies?

For example, I need to generate 10,000,000 rows, where there will be 10% of ‘a', 20% of ‘b', and the rest will be split equally between ‘c' and ‘d'?

Continue reading Picking random element, with weights

Waiting for PostgreSQL 16 – Add support for regexps on database and user entries in pg_hba.conf

On 24th of October 2022, Michael Paquier committed patch:

Add support for regexps on database and user entries in pg_hba.conf
 
As of this commit, any database or user entry beginning with a slash (/)
is considered as a regular expression.  This is particularly useful for
users, as now there is no clean way to match pattern on multiple HBA
lines.  For example, a user name mapping with a regular expression needs
first to match with a HBA line, and we would skip the follow-up HBA
entries if the ident regexp does *not* match with what has matched in
the HBA line.
 
pg_hba.conf is able to handle multiple databases and roles with a
comma-separated list of these, hence individual regular expressions that
include commas need to be double-quoted.
 
At authentication time, user and database names are now checked in the
following order:
- Arbitrary keywords (like "all", the ones beginning by '+' for
membership check), that we know will never have a regexp.  A fancy case
is for physical WAL senders, we *have* to only match "replication" for
the database.
- Regular expression matching.
- Exact match.
The previous logic did the same, but without the regexp step.
 
We have discussed as well the possibility to support regexp pattern
matching for host names, but these happen to lead to tricky issues based
on what I understand, particularly with host entries that have CIDRs.
 
This commit relies heavily on the refactoring done in a903971 and
fc579e1, so as the amount of code required to compile and execute
regular expressions is now minimal.  When parsing pg_hba.conf, all the
computed regexps needs to explicitely free()'d, same as pg_ident.conf.
 
Documentation and TAP tests are added to cover this feature, including
cases where the regexps use commas (for clarity in the docs, coverage
for the parsing logic in the tests).
 
Note that this introduces a breakage with older versions, where a
database or user name beginning with a slash are treated as something to
check for an equal match.  Per discussion, we have discarded this as
being much of an issue in practice as it would require a cluster to
have database and/or role names that begin with a slash, as well as HBA
entries using these.  Hence, the consistency gained with regexps in
pg_ident.conf is more appealing in the long term.
 
**This compatibility change should be mentioned in the release notes.**
 
Author: Bertrand Drouvot
Reviewed-by: Jacob Champion, Tom Lane, Michael Paquier
Discussion: https://postgr.es/m/fff0d7c1-8ad4-76a1-9db3-0ab6ec338bf7@amazon.com

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What is LATERAL, what is it for, and how can one use it?

Lately in couple of places I recommended people that they can solve their problem with queries using LATERAL. In some cases recipient of such suggestion indicated that they had no idea what LATERAL is. Which made me think that it might be good idea to write more about them (lateral queries)…

Also – I know that some of the examples I shown in here can be done differently, I just wanted to show how one can use LATERAL, and am terrible with coming up with better usecases.

Continue reading What is LATERAL, what is it for, and how can one use it?