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  • Using G-WAN C Servlets with PostgreSQL under Win32

    Posted by Peter / on 02/04/2010 / 0 Comments

    I have posted an example how to use G-WAN C Servlets with PostgreSQL. Check it out.

    G-WAN is a small-footprint (100 KB) Web server with C scripts executed in real-time (no compiler needed). G-WAN C scripts are as fast as static pages. It is much, much faster than Apache and IIS. More about it here


  • Per-table autovacuum parameters in PostgreSQL 8.4

    Posted by Ivan / on 02/10/2009 / 0 Comments

    A commit yesterday (by Alvaro Herrera, based on a patch by Euler Taveira de Oliveira) allows setting per-table autovacuum parameters directly from the CREATE/ALTER TABLE statement. For example, it is now possible to write:

    CREATE TABLE vacuumtest(...) WITH autovacuum_enabled=false

    For a complete list of supported parameters see the developers documentation.

  • Floyd-Warshal algorithm in PL/pgSQL

    Posted by Ivan / on 01/30/2009 / 1 Comment

    Maresa Nirwan has published a interesting blog post in which she implemented the Floyd-Warshal algorithm in pl/pgsql. The Floyd-Warshal deals with the degrees of separation in social networks. In other words it calculates the the shortest paths between all pairs of vertices in a graph.

  • Relative_Levenshtein UDF contribution

    Posted by IVO / on 01/27/2009 / 7 Comments

    The regular (classic) Levenshtein() function computes the minimum number of differences between 2 strings (replacements, deletions, insertions). It is a natural integer number - but it gives no clue how similar are the given strings. I have combined information from several different places in Internet (I do not remember the exact locations, but I do not pretend that I am the author - I just made the things work together) and the result is function Relative_Levenshtein(), which computes the similarity (fractional number between 0 and 1, inclusive) between 2 strings. I also changed the original Joe Conway`s realization of Levenshtein() function ..

  • Updatable views

    Posted by Ivan / on 01/23/2009 / 1 Comment

    PostgreSQL has had updatable views for a long time, via the rules system, but a commit from yesterdat (by Bernd Helmle) provides some automatic view update rules. It means that in PostgreSQL some views will be automatically updatable and commands like INSERT, UPDATE, and DELETE can be used on the view directly. A view is updatable if it does not contain:

    • more than one underlying table (joins) or no underlying table at all
    • underlying tables/views that are themselves not updatable
    • subqueries in the FROM list
    • items in the select list that are not direct references to a ..
  • SELECT...ORDER BY...FOR UPDATE/SHARE might return results out of order

    Posted by Ivan / on 01/23/2009 / 3 Comments

    Bruce Momjian just updated the documentation noting that a SELECT FOR UPDATE statement might actually return the results in an arbitrary order:

    Similarly, it is possible for a SELECT command using ORDER BY and FOR UPDATE/SHARE to return rows out of order. This is because ORDER BY is applied first. The command orders the result, but might then block trying to obtain a lock on one or more of the rows. Once the SELECT unblocks, one of the ordered columns might have been modified and be returned out of order. A workaround is to perform SELECT ... FOR UPDATE/SHARE and ..
  • Column-level privileges in PostgreSQL 8.4

    Posted by Ivan / on 01/23/2009 / 1 Comment

    Tom Lane just commited a patch providing column-level privileges in PostgreSQL, written by Stephen Frost and others. Here are some samples taken directly from the regression tests to show how this will work:

    CREATE TABLE atest5 (one int, two int, three int);
    CREATE TABLE atest6 (one int, two int, blue int);
    GRANT SELECT (one), INSERT (two), UPDATE (three) ON atest5 TO regressuser4;
    GRANT ALL (one) ON atest5 TO regressuser3;

    INSERT INTO atest5 VALUES (1,2,3);

    SELECT * FROM atest5; -- fail
    SELECT one FROM atest5; -- ok

    SELECT 1 FROM atest5 a JOIN atest5 ..

  • Добре дошли!

    Posted by Ivan / on 01/15/2009 / 0 Comments

    Добре дошли в първата българска PostgreSQL потребителска група. Най-важната ни цел в момента е набирането на нови членове. Така, че споделете с приятели, които имат опит с PostgreSQL и ги поканете да се присъединят.

    Целите на групата ще дефинираме като съберем поне 10 души.


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