Archive for March, 2009

Minor SVN hiccup

March 24th, 2009 by Sjan Evardsson

Anyone who tried to access SPDO via the subversion repo since Saturday may have run into a slight problem: namely a session that looked something like this:

ratatosk:svn sjan$ svn co http://www.evardsson.com/repos/projects/spdo/ spdo
svn: Could not open the requested SVN filesystem

I only became aware of it this morning, and I knew (almost) right away where the problem might lie. I was still able to access the repos via svn (in the internal network) and via file (from the server) but could not access them from http or https. I checked the svn version number and got this:

xxxx spdo # svn --version
svn, version 1.5.6 (r36142)
   compiled Mar 21 2009, 09:44:24

Copyright (C) 2000-2008 CollabNet.
Subversion is open source software, see http://subversion.tigris.org/
This product includes software developed by CollabNet (http://www.Collab.Net/).

The following repository access (RA) modules are available:

* ra_neon : Module for accessing a repository via WebDAV protocol using Neon.
  - handles 'http' scheme
  - handles 'https' scheme
* ra_svn : Module for accessing a repository using the svn network protocol.
  - with Cyrus SASL authentication
  - handles 'svn' scheme
* ra_local : Module for accessing a repository on local disk.
  - handles 'file' scheme

Ok, so this version built on Saturday when I did my latest updates. So, ra_svn works, ra_local works but ra_neon does not. I recalled that neon upgraded from 0.28.3 to 0.28.4 on the same day with the warning:

  * Neon has a policy of breaking API across minor versions, this means
 * that any package that links against neon may be broken after
 * updating. They will remain broken until they are ported to the
 * new API. You can downgrade neon to the previous version by doing:
 *
 *   emerge --oneshot '<net-misc/neon-0.28'
 *
 * You may also have to downgrade any package that has already been
 * ported to the new API.

That shouldn’t be needed (downgrading earlier than 0.28) since everything was working fine with 0.28.3 so, a quick

emerge --oneshot =net-misc/neon-0.28.3

and all is right with the world again.

SPDO 1.0b Release Candidate 1

March 8th, 2009 by Sjan Evardsson

SPDO version 1.0 beta Release Candidate 1 is out the door. This version adds the following:

Three custom Exception classes: SPDOError, ConnectionFailedError and ForeignKeyViolationError. Which are used (in order) when the program encounters an unknown sql error, a failure to connect to the database, and a violation of a foreign key constraint. Which means, of course, that foreign key constraints are now part of SPDO.

How this was accomplished is through the use of the new DbBuilder class. The DbBuilder class takes a multi-dimensional dict (Python) or array (PHP) of table and field data to build the tables and create triggers in MySQL and SQLite and add foreign keys in PostgreSQL. As an example consider the following:

In Python:

structure = {
    'authors':{
        'id':['primary_auto'],
        'first_name':['varchar(50)'],
        'last_name':['varchar(50)', 'NONULL', 'INDEX']
        },
    'books':{
        'id':['primary_auto'],
        'author_id':['int', "FK_CASCADE('authors','id')", 'INDEX'],
        'title':['varchar(100)','NONULL', 'INDEX']
        }
    }
dbb = DbBuilder(structure)
dbb.create()

In PHP:

$structure = array(
        'authors'=>array(
        'id'=>array('primary_auto'),
        'first_name'=>array('varchar(50)'),
        'last_name'=>array('varchar(50)', 'NONULL', 'INDEX')
    ),
    'books'=>array(
        'id'=>array('primary_auto'),
        'author_id'=>array('int', "FK_CASCADE('authors','id')", 'INDEX'),
        'title'=>array('varchar(100)','NONULL', 'INDEX')
    )
);
$dbb = DbBuilder($structure)
$dbb->create()

This results in the following queries to be executed:

In PostgreSQL:

CREATE TABLE authors (
    first_name VARCHAR(50) ,
    last_name VARCHAR(50) NOT NULL,
    id SERIAL PRIMARY KEY 
 );
CREATE TABLE books (
    author_id INTEGER ,
    id SERIAL PRIMARY KEY ,
    title VARCHAR(100) NOT NULL
);
CREATE INDEX authors_last_name_idx ON authors(last_name_id);
CREATE INDEX books_author_id_idx ON books(author_id);
CREATE INDEX books_title_idx ON books(title);
ALTER TABLE books ADD FOREIGN KEY (author_id) REFERENCES authors(id) ON DELETE CASCADE;

In MySQL:

CREATE TABLE authors (
    id INTEGER NOT NULL AUTO_INCREMENT PRIMARY KEY,
    first_name VARCHAR(50),
    last_name VARCHAR(50) NOT NULL
);
CREATE TABLE books (
    id INTEGER NOT NULL AUTO_INCREMENT PRIMARY KEY,
    author_id INTEGER NOT NULL,
    title VARCHAR(100) NOT NULL
);
CREATE TABLE fk_error_msg (
    error_msg VARCHAR(100) NOT NULL PRIMARY KEY
);
INSERT INTO fk_error_msg VALUES ('Foreign Key Constraint Violated!');
ALTER TABLE authors ADD INDEX(last_name);
ALTER TABLE books ADD INDEX(author_id);
ALTER TABLE books ADD INDEX(title);
CREATE TRIGGER fki_books_author_id
    BEFORE INSERT ON books
    FOR EACH ROW BEGIN
        IF
            0 = (SELECT COUNT(*) FROM authors WHERE id=new.author_id)
        THEN
            INSERT fk_error_msg VALUES ('Foreign Key Constraint Violated!');
        END IF;
    END;
CREATE TRIGGER fku_books_author_id
    BEFORE UPDATE ON books
    FOR EACH ROW BEGIN 
        IF
            0 = ( SELECT COUNT(*) FROM authors WHERE id = new.author_id )
        THEN
            INSERT INTO fk_error_msg VALUES ('Foreign Key Constraint Violated!');
        END IF ;
    END;
CREATE TRIGGER fkdc_books_author_id
    BEFORE DELETE ON authors
    FOR EACH ROW BEGIN
        DELETE FROM books WHERE author_id=old.id;
    END;

In SQLite:

CREATE TABLE authors (
    id INTEGER NOT NULL PRIMARY KEY,
    first_name VARCHAR(50),
    last_name VARCHAR(50) NOT NULL
);
CREATE TABLE books (
    id INTEGER NOT NULL PRIMARY KEY,
    author_id INTEGER NOT NULL,
    title VARCHAR(100) NOT NULL
);
CREATE INDEX authors_last_name_idx ON authors(last_name);
CREATE INDEX books_author_id_idx ON books(author_id);
CREATE INDEX books_title_idx ON books(title);
CREATE TRIGGER fki_books_author_id
    BEFORE INSERT ON [books]
        FOR EACH ROW BEGIN
            SELECT RAISE(ROLLBACK, 'insert on table "books" violates foreign key constraint "fki_books_author_id"')
            WHERE NEW.author_id IS NOT NULL AND (SELECT id FROM authors WHERE id = NEW.author_id) IS NULL;
        END;
CREATE TRIGGER fku_books_author_id
    BEFORE UPDATE ON [books]
        FOR EACH ROW BEGIN
            SELECT RAISE(ROLLBACK, 'update on table "books" violates foreign key constraint "fku_books_author_id"')
            WHERE NEW.author_id IS NOT NULL AND (SELECT id FROM authors WHERE id = NEW.author_id) IS NULL;
        END;
CREATE TRIGGER fkdc_books_author_id
    BEFORE DELETE ON authors
        FOR EACH ROW BEGIN
            DELETE FROM books WHERE books.author_id = OLD.id;
        END;

Be sure to check out the wiki, and the source code is all readable there, or download and enjoy. There are still a few edits that need to happen in the comments (like versions need to be updated, and changelogs added and there are a few typos probably still lurking about.)