How to install your own copy of explain.depesz.com

There are some cases where you might want to get your own copy of explain.depesz.com. You might not trust me with your explains. You might want to use it without internet access. Or you just want to play with it, and have total control over the site.

Installing, while obvious to me, and recently described by John Poole, is not always 100% clear. So, I decided to write about how to set it up, from scratch.

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Changes on explain.depesz.com

Uploaded new version to the server – straight from GitHub. There are two changes – one visible, and one not really.

The invisible change, first, is one for people hosting explain.depesz.com on their own. As you perhaps know you can get sources of explain.depesz.com and install it on any box you want (as log as you can get there PostgreSQL, Perl, and some perl modules). While working on it on my own, I figured I could use a way to tell which version of module-xxx the site is running right now. So I build /info page (which is inaccessible to everyone, but manually-marked admins), which lists versions and interesting paths.

The second change – the one visible to users, is that I made explain.depesz.com commify numbers. Sometimes it can be hard to read value like 12325563, but now it will be displayed as 12,325,563 making is simpler to grasp.

This second change was suggested by Jacek Wielemborek, so if you hate it – blame him. Of course if you love the change – it's all on me 🙂

Hope you'll find it helpful.

Anonymize CTE names on explain.depesz.com

A colleague recently let me know that anonymization in explain.depesz.com doesn't handle CTE names. For example, in plan:

                                            QUERY PLAN                                             
---------------------------------------------------------------------------------------------------
 CTE Scan on some_name  (cost=0.01..0.03 rows=1 width=8) (actual time=0.027..0.028 rows=1 loops=1)
   CTE some_name
     ->  Result  (cost=0.00..0.01 rows=1 width=0) (actual time=0.023..0.023 rows=1 loops=1)
 Planning time: 0.217 ms
 Execution time: 0.124 ms
(5 rows)

“some_name" was kept even if anonymization was turned on.

Now it's fixed, and new code should properly anonymize all CTE names. Of course the change is live on explain.depesz.com too.

Adding plans to explain.depesz.com from your psql

So, lately I have been thinking about integrating explain.depesz.com with psql. Currently, you have to run explain, copy the output, switch to webbrowser, go to explain.depesz.coma> site, paste output, click submit. It's not that it's a lot of work, but it can be simplified.

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Changes on explain.depesz.com

One of the features that is actually disliked is anonymization. But, regardless of the dislike – it has some users. And one of the user mailed me with information about a bug – namely – foreign table file names were not anonymized.

So, I wrote a patch, tests, released new version of underlying parsing library.

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Change in anonymization of plans on explain.depesz.com

As you perhaps know, explain.depesz.com has anonymization feature.

Couple of days ago Filip contacted me and sent a patch that stopped anonymization of typecasts.

I thought about the patch, and what it achieves, changed it's internals, but kept the effect. And today, it got released.

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Waiting for 9.2 – filtered info in explain analyze

On 22nd of September, Tom Lane committed patch:

Make EXPLAIN ANALYZE report the numbers of rows rejected by filter steps.
 
This provides information about the numbers of tuples that were visited
but not returned by table scans, as well as the numbers of join tuples
that were considered and discarded within a join plan node.
 
There is still some discussion going on about the best way to report counts
for outer-join situations, but I think most of what's in the patch would
not change if we revise that, so I'm going to go ahead and commit it as-is.
 
Documentation changes to follow (they weren't in the submitted patch
either).
 
Marko Tiikkaja, reviewed by Marc Cousin, somewhat revised by Tom

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