Month: July 2012

Pg::SQL::Parser

Some time ago I was looking (warning: post in polish) for someone to teach me proper parsing.

One of really great polish Perl programmers – Dozzie – reached out, and helped me. By the way – thanks a lot, Dozzie.

Based on what he taught me, I started writing module for parsing SQL queries. By that I mean proper parsing, with grammar (using Parse::Eyapp), and not set of regular expressions.

My parser is not ready. To say it lightly. Very lightly.

For now, it just knows how to parse the simplest queries like:

  • select 1;
  • select ‘a' as b;

I am working very slowly on it, so don't expect any usable version in any defined future. I will get there, eventually, but it is a project that I work on in my free time, after I finish everything else that I could work on in given moment.

This post is intended to announce that I'm working on it (so I will have kind of obligation to do it). And, if anyone is interested – I more than welcome all contributors/reviewers, and perhaps even critics 🙂

Final note – if you'll review the code, and want to comment on ugly list of regexps in Lexer – I know. It will be eventually replaced by one regular expression, but since it will be regular expression built by Regexp::Optimizer – it will not really be readable (though it will be faster than current approach).

Waiting for 9.3 – Event triggers

On 20th of July, Robert Haas committed patch:

Make new event trigger facility actually do something.
 
Commit 3855968f328918b6cd1401dd11d109d471a54d40 added syntax, pg_dump,
psql support, and documentation, but the triggers didn't actually fire.
With this commit, they now do.  This is still a pretty basic facility
overall because event triggers do not get a whole lot of information
about what the user is trying to do unless you write them in C; and
there's still no option to fire them anywhere except at the very
beginning of the execution sequence, but it's better than nothing,
and a good building block for future work.
 
Along the way, add a regression test for ALTER LARGE OBJECT, since
testing of event triggers reveals that we haven't got one.
 
Dimitri Fontaine and Robert Haas

This was preceded (two days earlier) by commit, also by Robert Haas, which stated:

Syntax support and documentation for event triggers.
 
They don't actually do anything yet; that will get fixed in a
follow-on commit.  But this gets the basic infrastructure in place,
including CREATE/ALTER/DROP EVENT TRIGGER; support for COMMENT,
SECURITY LABEL, and ALTER EXTENSION .. ADD/DROP EVENT TRIGGER;
pg_dump and psql support; and documentation for the anticipated
initial feature set.
 
Dimitri Fontaine, with review and a bunch of additional hacking by me.
Thom Brown extensively reviewed earlier versions of this patch set,
but there's not a whole lot of that code left in this commit, as it
turns out.

Continue reading Waiting for 9.3 – Event triggers

Waiting for 9.3 – Add array_remove() and array_replace() functions.

On 11th of July, Tom Lane committed patch:

Add array_remove() and array_replace() functions. <span class="refs"> <span class="head" title="heads/master"><a href="/gitweb/?p=postgresql.git;a=shortlog;h=refs/heads/master">master
 
These functions support removing or replacing array element value(s)
matching a given search value.  Although intended mainly to support a
future array-foreign-key feature, they seem useful in their own right.
 
Marco Nenciarini and Gabriele Bartolini, reviewed by Alex Hunsaker

Continue reading Waiting for 9.3 – Add array_remove() and array_replace() functions.

Waiting for 9.3 – Dramatically reduce System V shared memory consumption.

On 28th of June, Robert Haas committed patch:

Dramatically reduce System V shared memory consumption.
 
Except when compiling with EXEC_BACKEND, we'll now allocate only a tiny
amount of System V shared memory (as an interlock to protect the data
directory) and allocate the rest as anonymous shared memory via mmap.
This will hopefully spare most users the hassle of adjusting operating
system parameters before being able to start PostgreSQL with a
reasonable value for shared_buffers.
 
There are a bunch of documentation updates needed here, and we might
need to adjust some of the HINT messages related to shared memory as
well.  But it's not 100% clear how portable this is, so before we
write the documentation, let's give it a spin on the buildfarm and
see what turns red.

Continue reading Waiting for 9.3 – Dramatically reduce System V shared memory consumption.

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.

Continue reading Changes on explain.depesz.com

OmniPITR 1.0.0 released

Finally, after all these years, version 1.0.0 of OmniPITR got Released.

The reason I went to 1.0.0, and not 0.8.0 is very simple – finally, all programs in bin/ actually work 🙂

By that I mean: since beginning there was “omnipitr-monitor" – which simply didn't work, because work on it was always postponed. But now, it does. It's functionality is not all that great now, but it works, checks some basic data about replication, and can be used in production.

Now, there is still a todo but these things are less important.

I have to say that writing, and maintaining OmniPITR taught me a lot about PostgreSQL – how it works, and what really WAL is. It was really cool.