On 7th of February, Robert Haas committed patch:
Sometimes it may be useful to get actual row counts out of EXPLAIN (ANALYZE) without paying the cost of timing every node entry/exit. With this patch, you can say EXPLAIN (ANALYZE, TIMING OFF) to get that. Tomas Vondra, reviewed by Eric Theise, with minor doc changes by me.
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
Continue reading Waiting for 9.2 – filtered info in explain analyze
Just updated explain.depesz.com site with new functionality – when showing parsed plan, there is new tab “stats". In there you can see some basic statistics of the query, used types of nodes, and tables that were used by it.
There are probably some problems with stats (it's new functionality, so bugs are imminent), but
As usual, some stats need to be added 🙂
First of all, as of today, I added new feature, called anonymization.
It is for all of the people who are afraid that their plans contain information that they don't want to (or can't) share on the internet.
It works like this:
Continue reading explain.depesz.com – new feature and some new stats
Today, I released 2 new versions (new features in 0.5, and then quick bugfix in 0.51) of Pg::Explain Perl library.
This is the base of explain.depesz.com – the code that does heavy lifting of parsing plans, and providing them in uniform way (object).
Thanks to enormous work done by Łukasz ‘metys' Lewandowski, explain.depesz.com page is no longer “desiged by depesz" (which is a code for “ugly as hell"), but is nice, and good looking.
If you like it, please do send some thank you note to Łukasz – he blogs in Polish, but he reads and understands English too.
Change is not only skin deep. The whole site has been rewritten, and uses now Mojolicious web framework instead of Catalyst.
This change should be a welcome surprise to anyone willing to setup their own copy of the site for top-secret plans from their company – mostly because number of dependencies dropped significantly.
All in all – have fun, and thanks for using the site.
First of all – just today I committed patch for Pg::Explain – which is the workhorse behind explain.depesz.com.
This patch fixes calculation of exclusive time for explain nodes, and the best thing about it is – I didn't write it. It's full patch provided by someone else – Filip Rembiałkowski – my former colleague, friend, and PostgreSQL DBA (not olny PG!).
This is (as far as I recall) first patch that was provided to me for this library, and I'm really grateful for the contribution.
New version of Pg::Explain will hit CPAN mirrors shortly (it's already uploaded, now we're waiting for CPAN mirrors to get it).
When I was updating it, I checked state of database. And I learned that explain.depesz.com is over 2 years now! Some stats follow.
This question (and its variants) show quite often on #postgresql on IRC. People get sequential scans, and are worried that it's slow and bad.
So, I hope that this blogpost will shed some light on the subject why indexes are being chosen to be used, or not.
I just checked, and apparently explain.depesz.com is online for over a year now. First plans was added on 2008-12-04 13:20:43+01.
Since then there have been 3602 plans added, 770 of them were set to be private (not displayed on previous explains page.
Longest plan has 2267194 characters (yes, 2.2 megabytes of explain analyze output!), but it's not public, so I can't tell you the url. Longest public plan is this monstrosity, which (while being only explain output, not explain analyze) has 503585 characters.
During this time, there have been 61 days that nobody added any plan on (perhaps problems with software?).
The most heavily used day was 23rd of June 2009, when 71 new plans have been added (4 private).
Thank you all for using it. I hope you find it useful, and I promise, that one day, I will finally sit down, and add all long-due features (like work with new explain formats, fixing some output glitches, stats of used objects per plan).
If you'd like to take a peek at how it works – source of explain.depesz.com is always available.
Today small, but (at least for me) really useful patch. Committed on 15th of December by Robert Haas, and written by Itagaki Takahiro, this patch does:
Log Message: ----------- Add an EXPLAIN (BUFFERS) option to show buffer-usage statistics. This patch also removes buffer-usage statistics from the track_counts output, since this (or the global server statistics) is deemed to be a better interface to this information. Itagaki Takahiro, reviewed by Euler Taveira de Oliveira.