Starting Work On Object Database In Python

15 Aug 2008 10:08

Good morning everyone,

today I start working on object database to be implemented in Python. This is my individual project for my classes.

During the study-year I was taught how to parse sophisticated grammar with PLY (Python Lex and Yacc library). I've then learned how to then process the parsed queries, to get the results.

The database query language is similar to the SQL language. The difference is, we don't have definitions of tables and fields. Any object (row in table) can have fields other that other objects with the same name (of the same table).

This seems quite hard, but it has its pros.

Moreover we've analyzed the following query using the simple parsing and processing:

SELECT employee.salary WHERE employee.salary > AVG(employee.salary);

now, having as much as 10000 employees, using the standard processing, this would mean calculating the average (AVG) from ALL salaries for EACH of the 10000 employees.

So the teacher proposed to use tree decoration, to mark the branches of the query syntax tree, that can be run once (i.e. their value does not depend on the rest of the query).

I proposed to do it other way: to don't analyze the tree to much, but instead implement a sort of caching. Each time we try to get the AVG(employee.salary) we check whether this was already calculated, if not (only the first time we get the AVG), we calculate this and populates the cache with the value.

This has the following pros:

  • we can use the cache in successive queries
  • we don't have to decorate query trees — it's not Christmas here

Today work I start with selecting a Python IDE to work with. During the classes I used PyDev — the Python plugin for Eclipse IDE, but I believe there any many new choices out there now — after a few months:

  • eric
  • pida
  • geany
  • drpython

(all from Ubuntu default repository)

More IDEs I found with Google:

Comments: 2

More Juice

07 Aug 2008 14:12

Hi, today we've put more juice to Wikidot.

Here is automatic reflection generation:

wikidot-grass.png

Wonder how?

[[embed]]
<script type="text/javascript" src="http://static.wikidot.com/common--misc/reflection.js"></script>
[[/embed]]
[[div style="background: #444; padding: 20px; overflow: auto"]]
[[div style="margin: 0 auto; width: 400px"]]
[[image http://qn.lastlook.pl/~quake/wikidot-grass.png class="reflect rheight32 ropacity40"]]
[[/div]]
[[/div]]

We've also added many new video services to Wikidot (through [[embed]] tag) and more…

Comments: 3

Why Wikidot Rulez

04 Aug 2008 14:39

Have you ever wondered why Wikidot rulez?

You could say, "hey, there is much more other wiki hosts out there, why should I use Wikidot?"

Wetpaint look quite nice, but has anoying Google Ads everywhere. (I've read, they have $40 million capital).

Wikia has the strange permission thing — if you post anything, it becomes their property.

PbWiki didn't allowed me to upload HTML file like this:

<html>
<head>
<title></title>
</head>
<body>
abc bac
</body>
</html>

It claimed, that this is a spam and disabled file upload for 15 minutes for all pbwiki sites!

In the contrary Wikidot has many friendly features1 and have a totally different ads policy. Actually, they let YOU earn with their service. If you wish to display ads on your wiki, you get as much as 80% of what Google pays for them.

Wikidot rules, and has everyday-growing community, with their masterpiece wiki at http://community.wikidot.com/.

Comments: 0

Footnotes

A Lot!

01 Aug 2008 23:10

- How much do you hate IE?
- A lot!
- That's enough, welcome in our team.

With the news about new team member, new themes and major software improvement it seems, that here, at Wikidot, we work hard. And as a matter of fact, we do.

I've recently created two nice themes for Wikidot:

  • Bloo — especially for bloggers and a variant of this Bloo - no sidebar
  • Not-yet-named (codename booze) — the one that is used on the http://themes.wikidot.com/

The latter was designed with much help from SquarkSquark — the new team member.

Other interesting facts from the behind of scenes, with the server software upgrade, we've fixed some bugs, including:

  • browsing by tags now allows special characters like + in tags
  • printer-friendly version of forum was fixed (actually it seems that this had never worked before)

Moreover, we've injected more magic to Wikidot. The greatest improvements are:

  • serving user-uploaded files. PHP checks whether you have right to see the file and then instructs the Lighttpd web server to serve the file to the user. We're using X-LIGHTTPD-sendfile for this purpose. Moreover we're now using a totally different domain for this: *.wdfiles.com, which prevents from JavaScripts attacks.
  • direct access to any code block inside wikis. Just append /code to the URL
Example codeblock, that is accessible with a custom URL:
http://piotr.gabryjeluk.pl/dev:a-lot/code

Moreover if you set the type of the code to html or css, Wikidot will serve the file with the proper MIME type which makes the codes usable as external style sheets or iframe destinations!

See the following codes:

<html>
    <head>
        <title>Wikidot extracts codes from wiki pages!</title>
        <link rel="stylesheet" type="text/css" href="http://piotr.gabryjeluk.pl/dev:a-lot/code/3"/>
    </head>
    <body>
        <p>HTML live-extracted from page's code with attached live-extracted style!</p>
    </body>
</html>
p {
    border: dashed #f00 1px;
    background: #ffa;
    color: #f00;
    font-weight: bold;
    font-size: 40px;
}

Now the trick. To access the second (and any other) code block, just supply the URL of the page following by /code/<number>

for example

http://piotr.gabryjeluk.pl/dev:a-lot/code/2

will point you to the second code block in the http://piotr.gabryjeluk.pl/dev:a-lot page.

Now the Live demo:

Cool, huh? No file uploads needed, just save the code at Wikidot page and… access it!

Comments: 2

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