Understanding postgresql.conf : checkpoint_completion_target

Starting new blog series – explanation of various configuration parameters.

I will of course follow no schedule or order – if I'd had to – it would be my job, and in this way – it's fun.

First configuration parameter to write about is checkpoint_completion_target.

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Waiting for 8.5 – GUC per user and database

On 7th of October Alvaro Herrera committed his own patch, which adds quite interesting possibilty:

Log Message:
-----------
Make it possibly TO specify GUC params per USER AND per DATABASE.
 
CREATE a NEW catalog pg_db_role_setting WHERE they are now stored, AND better
encapsulate the code that deals WITH settings INTO its realm.  The OLD
datconfig AND rolconfig COLUMNS are removed.
 
psql has gained a \drds command TO display the settings.
 
Backwards compatibility warning: while the backwards-compatible system views
still have the config COLUMNS, they no longer completely represent the
configuration FOR a USER OR DATABASE.
 
Catalog version bumped.

Continue reading Waiting for 8.5 – GUC per user and database

Getting session variables without touching postgresql.conf

This post has been updated with new code that uses temporary table – the code is at the end of post!

There was this question on Stack Overflow.

For future reference: guy asked how to do session variables – i.e. something he could define once in session, and later reuse in standard sql queries – without modifying postgresql.conf – so usage of custom_variable_classes is forbidden 🙂

While I don't actually see why somebody would want to avoid modifying its postgresql.conf (short of “it's shared hosting and I don't have superuser privileges"), I thought that it will be rather simple, and at the same time, rather interesting.

So, let's do it:

Continue reading Getting session variables without touching postgresql.conf

Waiting for 8.5 – Add log_line_prefix placeholder %e to contain the current SQL state

Also yesterday, and also Peter Eisentraut, committed patch by Guillaume Smet, which:

Add log_line_prefix placeholder %e to contain the current SQL state
 
Author: Guillaume Smet

Continue reading Waiting for 8.5 – Add log_line_prefix placeholder %e to contain the current SQL state