New work-related blog (på svenska!)

Finally got inspired to setup a work-related blog at blogger: http://fredrik-at-pingpong.blogspot.com/

Indentation problem when pasting into vim and the nopaste option

When pasting content into vim, such as a code snippet, it may mess up the indentation in a nested kind of way, with indentation increasing the further down you go.

The vim paste option fixes this - just issue :vim paste before pasting, and :vim nopaste when done.

As noted by the vim documentation, the underlying problem is that a terminal program, in contrast to a GUI one, may not recognize the difference between pasted and typed text.

Java app to send geocaching data to your Nokia phone

I have documented a small java app that's useful for me that allows me to send geocaching information from geocaching.com to Nokia phones. See http://fornwall.net/landmarksender/ for more information.

Session variables in postgresql

Consider a trigger that would like to prevent certain operations when executed by a web application, while allowing the operations when performed by a nightly batch job.

One way to solve this is to use a kind of session variables. The trigger lets the operation execute normally only if a session variable is set, which the batch job sets at the start of the execution. Below is an example illustrating one implementation for this in PostgreSQL.

First, we define a kind of namespace for our session variable (a customized option or variable class in postgres lingo) in postgresql.conf:

# comma-separated list of class names:
custom_variable_classes = 'myvariableclass'

Now, consider the following table:

CREATE TABLE my_table (ID INTEGER);
INSERT INTO my_table VALUES (1);

A trigger is to prevent DELETE:s from that table unless the session variable myvariableclass.idontcare is set:

CREATE OR REPLACE FUNCTION prevent_delete_unless_idontcare() RETURNS TRIGGER AS $$
DECLARE
  idontcare TEXT;
BEGIN
  SELECT INTO idontcare CURRENT_SETTING('myvariableclass.idontcare');
  IF (idontcare != 'true') THEN
    RAISE EXCEPTION 'Not allowed to delete unless myvariableclass.idontcare is true';
  END IF;
  RETURN NULL;
END;
$$ LANGUAGE plpgsql;

CREATE TRIGGER prevent_delete_unless_idontcare_trigger
AFTER DELETE ON my_table
FOR EACH ROW EXECUTE PROCEDURE prevent_delete_unless_idontcare();

Now let's see it in action:

fornwall=> DELETE FROM my_table;
ERROR:  Not allowed to delete unless myvariableclass.idontcare is true
fornwall=> SELECT SET_CONFIG('myvariableclass.idontcare', 'true', FALSE);
 set_config 
------------
 true
(1 row)

fornwall=> DELETE FROM my_table;
DELETE 1

See postgres documentation for the current_setting and set_config functions.

PyS60 script to summarize top persons in SMS inbox and outbox

This requires the latest version of PyS60 (1.9.x):

# -*- coding:utf-8 -*-
import appuifw, collections, e32, inbox

def summarize_box(box, box_name):
    counter = collections.defaultdict(int)
    for message_id in box.sms_messages():
            counter[box.address(message_id)] += 1

    content = "Persons in " + box_name + ":\n"
    for (name, count) in sorted(counter.iteritems(), key=lambda (x,y):(y,x), reverse=True):
        content += u"%-3d: %s\n" % (count, name)

    return content

content = summarize_box(inbox.Inbox(), 'Inbox')
content += "\n"
content += summarize_box(inbox.Inbox(inbox.ESent), 'Sent')

lock = e32.Ao_lock()
appuifw.app.body = appuifw.Text(content)
appuifw.app.exit_key_handler = lock.signal
lock.wait()

Tip: What to try when autocomplete stops working for java in eclipse

Suddenly (?) the autocomplete functionality of the java editor in eclipse stopped working. Searching for "eclipse autocomplete not working" on google quickly found a cure:

1. Go Preferences>Java>Editor>Content Assist>Advanced
2. Make sure “Other Java Proposals” is ticked

Size of a postgresql database

The size of a postgresql database can be obtained using the following query:

$ select pg_size_pretty(pg_database_size('database_name'));
 pg_size_pretty 
----------------
 70 GB
(1 row)