Tag: explain

Waiting for PostgreSQL 17 – Invent SERIALIZE option for EXPLAIN.

On 3rd of April 2024, Tom Lane committed patch:

Invent SERIALIZE option for EXPLAIN.
 
EXPLAIN (ANALYZE, SERIALIZE) allows collection of statistics about
the volume of data emitted by a query, as well as the time taken
to convert the data to the on-the-wire format.  Previously there
was no way to investigate this without actually sending the data
to the client, in which case network transmission costs might
swamp what you wanted to see.  In particular this feature allows
investigating the costs of de-TOASTing compressed or out-of-line
data during formatting.
 
Stepan Rutz and Matthias van de Meent,
reviewed by Tomas Vondra and myself
 
Discussion: https://postgr.es/m/ca0adb0e-fa4e-c37e-1cd7-91170b18cae1@gmx.de

Continue reading Waiting for PostgreSQL 17 – Invent SERIALIZE option for EXPLAIN.

Display “settings” from plans on explain.depesz.com

Some time ago I wrote about new options for explains – one that prints settings that were modified from default.

This looks like this:

Aggregate  (cost=35.36..35.37 rows=1 width=8)
  ->  Index Only Scan using pg_class_oid_index on pg_class  (cost=0.27..34.29 rows=429 width=0)
Settings: enable_seqscan = 'off'

Finally, today, I pushed a change that displays them on explain.depesz.com. To make it more usable, it will also provide links to documentation about each such options.

For example, check this plan.

Hope you'll find it useful.

Buffers I/O information on explain.depesz.com

I just released first version of change to explain.depesz.com that displays buffer I/O information, as described recently.

You can see it in here.

There are two new columns in there, showing how much data given node read from disk, and how much it wrote.

It's definitely not 100% OK now, as you can see, speed and time is not always there, but generally it should work.

There is also summarized info in stats page of the explain.

If you'd notice anything wrong, please let me know, either by mail, or just make an issue on GitLab.

Many changes on explain.depesz.com

Some time ago Eugen Konkov mailed me that he'd like to have some changes on explain.depesz.com.

One of the changes was actual bug, but the rest were improvements to functionality.

I kinda didn't want to do it, but when I looked closer it appeared to me that there are some subtle bugs, and when I'll be fixing them, I can add some of the things Eugen requested:

Continue reading Many changes on explain.depesz.com

Million explain plans…

Back in 2007 I wrote a simple script to add total time to explain analyze output.

It was very helpful, for me.

Then, around a year later figured that it could be useful for others, so wrote a simple site that got plans, and displayed them with extra info. It didn't look great.

Two years later I figured it would be good to make it look nicer. Asked a friend – Łukasz Lewandowski about it, and together we made new version, that was easier on eyes.

Since then there were no layout changes, just some new functionality: deleting plans, anonymizing/obfuscating them, user accounts, plan stats.

The site seemed to catch. In the first month (December of 2008) there were 391 plans added. Almost exactly 10 years later, in October 2018, we got 394 plans added, on average, each day.

Lately the average daily count of new plans (monthly average) is 400-550.

The best day was 21st of February 2019 where we got 5320 new plans. Most likely due to link to site being posted on some news aggregator or forum.

And, just yesterday, at around 4:30pm UTC, there was millionth plan pasted.

That is amazing and I would like to thank all of you – it really brightens my day when I see that people are using the site, and it (hopefully) helps them.

Changes on explain.depesz.com – extracted query from auto-explain plans

Some time ago James Courtney reported missing functionality.

Specifically, when one uses auto-explain, logged explains contain query text. So, when such explain is then pasted on explain.depesz.com, it stands to reason that it should be able to extract the query on its own, without having to manually extract it and put it in query box.

It took me a while, but finally, got it working today. And you can see it in all four explain format:

Also, while I'm writing – it seems that somewhere next month, there will be 1 millionth plan uploaded to the site 🙂 Hope you all find it useful 🙂