Tag: postgresql

Waiting for PostgreSQL 11 – Support parallel btree index builds.

Support parallel btree index builds.
 
 
To make this work, tuplesort.c and logtape.c must also support
parallelism, so this patch adds that infrastructure and then applies
it to the particular case of parallel btree index builds.  Testing
to date shows that this can often be 2-3x faster than a serial
index build.
 
The model for deciding how many workers to use is fairly primitive
at present, but it's better than not having the feature.  We can
refine it as we get more experience.
 
Peter Geoghegan with some help from Rushabh Lathia.  While Heikki
Linnakangas is not an author of this patch, he wrote other patches
without which this feature would not have been possible, and
therefore the release notes should possibly credit him as an author
of this feature.  Reviewed by Claudio Freire, Heikki Linnakangas,
Thomas Munro, Tels, Amit Kapila, me.
 
Discussion: http://postgr.es/m/CAM3SWZQKM=Pzc=CAHzRixKjp2eO5Q0Jg1SoFQqeXFQ647JiwqQ@mail.gmail.com
Discussion: http://postgr.es/m/CAH2-Wz=AxWqDoVvGU7dq856S4r6sJAj6DBn7VMtigkB33N5eyg@mail.gmail.com

Continue reading Waiting for PostgreSQL 11 – Support parallel btree index builds.

Fix for parallel scans on explain.depesz.com

On Friday, Zr40 reported on irc that explain.depesz.com doesn't show table/index names for Parallel Seq Scan nodes.

Checked it and found couple of other omissions of the same kind with other Parallel* scans.

Fixed (I hope) all of them in:

The change is not really big, but just figured I'll let you know.

Waiting for PostgreSQL 11 – Allow UPDATE to move rows between partitions.

On 19th of January 2018, Robert Haas committed patch:

Allow UPDATE to move rows between partitions.
 
 
When an UPDATE causes a row to no longer match the partition
constraint, try to move it to a different partition where it does
match the partition constraint.  In essence, the UPDATE is split into
a DELETE from the old partition and an INSERT into the new one.  This
can lead to surprising behavior in concurrency scenarios because
EvalPlanQual rechecks won't work as they normally did; the known
problems are documented.  (There is a pending patch to improve the
situation further, but it needs more review.)
 
Amit Khandekar, reviewed and tested by Amit Langote, David Rowley,
Rajkumar Raghuwanshi, Dilip Kumar, Amul Sul, Thomas Munro, Álvaro
Herrera, Amit Kapila, and me.  A few final revisions by me.
 
Discussion: http://postgr.es/m/CAJ3gD9do9o2ccQ7j7+tSgiE1REY65XRiMb=yJO3u3QhyP8EEPQ@mail.gmail.com

Continue reading Waiting for PostgreSQL 11 – Allow UPDATE to move rows between partitions.

Waiting for PostgreSQL 11 – Add hash partitioning.

On 9th of November 2017, Robert Haas committed patch:

Add hash partitioning.
 
Hash partitioning is useful when you want to partition a growing data
set evenly.  This can be useful to keep table sizes reasonable, which
makes maintenance operations such as VACUUM faster, or to enable
partition-wise join.
 
At present, we still depend on constraint exclusion for partitioning
pruning, and the shape of the partition constraints for hash
partitioning is such that that doesn't work.  Work is underway to fix
that, which should both improve performance and make partitioning
pruning work with hash partitioning.
 
Amul Sul, reviewed and tested by Dilip Kumar, Ashutosh Bapat, Yugo
Nagata, Rajkumar Raghuwanshi, Jesper Pedersen, and by me.  A few
final tweaks also by me.
 
Discussion: http://postgr.es/m/CAAJ_b96fhpJAP=ALbETmeLk1Uni_GFZD938zgenhF49qgDTjaQ@mail.gmail.com

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Waiting for PostgreSQL 11 – Add psql variables to track success/failure of SQL queries.

On 12nd of September 2017, Tom Lane committed patch:

Add psql variables to track success/failure of SQL queries.
 
 
This patch adds ERROR, SQLSTATE, and ROW_COUNT, which are updated after
every query, as well as LAST_ERROR_MESSAGE and LAST_ERROR_SQLSTATE,
which are updated only when a query fails.  The expected usage of these
is for scripting.
 
Fabien Coelho, reviewed by Pavel Stehule
 
Discussion: https://postgr.es/m/alpine.DEB.2.20..12290@lancre

Continue reading Waiting for PostgreSQL 11 – Add psql variables to track success/failure of SQL queries.

Waiting for PostgreSQL 11 – Add \gdesc psql command.

On 5th of September 2017, Tom Lane committed patch:

Add \gdesc psql command.
 
This command acts somewhat like \g, but instead of executing the query
buffer, it merely prints a description of the columns that the query
result would have.  (Of course, this still requires parsing the query;
if parse analysis fails, you get an error anyway.)  We accomplish this
using an unnamed prepared statement, which should be invisible to psql
users.
 
Pavel Stehule, reviewed by Fabien Coelho
 
Discussion: https://postgr.es/m/CAFj8pRBhYVvO34FU=EKb=nAF5t3b++krKt1FneCmR0kuF5m-QA@mail.gmail.com

Continue reading Waiting for PostgreSQL 11 – Add \gdesc psql command.

New functions in versioning

Long time ago I wrote about my project – Versioning.

Since then nothing really changed. But recently I found a case where I could use some more logic from versioning, so I changed it. In proceess, I also added somewhat better docs.

The change itself is that now, when you write patch using Versioning you can add some assertions about the user that will be loading the patch, like:

  • SELECT _v.assert_user_is_superuser();
  • SELECT _v.assert_user_is_not_superuser();
  • SELECT _v.assert_user_is_one_of( ‘depesz', ‘postgres', ‘dba' );

Not a big change, but helps me quite a bit.

explain.depesz.com, paste.depesz.com – TOR announcement and some updates

I assume that you're familiar with explain.depesz.com and paste.depesz.com services.

From today they are also available as services in TOR, using respectively: explain4pg4j5wbw.onion and paste4sql64vzyry.onion (of course you need to have TOR Browser or some other way to browse darknet).

Why I did that? Well, I believe that TOR is one of the greatest inventions ever, and I'd like to do something so that it will be less associated with drugs, porn, or other illegal activities. Don't realistically think that there will be many people using TOR to access my Pg-related services, but it is a thing that I could have done, so I did it.

While working on it, I also updated pgFormatter code under paste-site to newest version.

Continue reading explain.depesz.com, paste.depesz.com – TOR announcement and some updates