Sometimes we have some special need for a stored procedure to call another to do something. That is fine, but what if the second stored proc failed for some reason? Maybe you want to halt the first stored procedure (the caller) and not proceed with the work until the problem is verified and resolved. So How do you do it?

Simple, get a return code from the called procedure to determine if it worked or not!

Here’s a sample piece of code to explain better:


DROP PROCEDURE IF EXISTS `test`.`testing123`;
DELIMITER $$

CREATE
PROCEDURE `test`.`testing123`(OUT a INT)
BEGIN
DECLARE EXIT HANDLER FOR SQLEXCEPTION
BEGIN
SET a=2;
END;
SET a=0;

# toggle the below as comment or not to see the call at the bottom working
# if you uncomment select abc you'll see the error, otherwise all is cool

# select abc;

…

As a continuation to a previous blog post last week and inspired by Kedar I have created a small script to export tables, stored procedures, functions and views into their respective file. It works for multiple databases where you can specify a list of databases too and although things like events, triggers and such are still missing they are easily added.

It is especially useful to dump stored procedures separately since it is a lacking functionality in mysqldump.

I placed the script in mysql forge for anybody to use, provide feedback and possibly enhancements to it.

If you like to keep your ddl backed up in some source management tool like svn or cvs and want to do it individually for stored procedures, events, triggers, tables and such rather than having a single file you can easily do so using the below. You could even include the –skip-dump-date or –skip-comments and use the below to compare ddl daily checking for alterations thus making sure you are aware of any ddl changes done on the database.

user=backup_user
password=`cat ~/.backup_password`
hostname=127.0.0.1
port=3306
dbname=test_db
path=/home/mysql/ddl
date=`date +%Y%m%d`

mysqldump -u$user -p$password -h$hostname -P$port --no-create-info --no-data --no-create-db --skip-opt $dbname > "$path"/"$dbname"_triggers_"$date".sql
mysqldump -u$user -p$password -h$hostname -P$port --routines --skip-triggers --no-create-info --no-data --no-create-db --skip-opt $dbname > …

By now you know that there is a MySQL Track during next week’s ODTUG Kaleidoscope in Washington, DC. Ronald Bradford and I organized the schedule at the last minute (Ronald did a lot of the work!). It was difficult to fill a schedule with 19 sessions that are either 1 hour or 1.5 hours long, and to do it I ended up with three presentations.

At each presentation I will be giving away a copy of The MySQL Administrator’s Bible, so be sure to show up! All MySQL track sessions are in Maryland C, and all times are Eastern.

On Monday, June 28th from 4 pm – 5:30 pm I will be presenting …

OverviewWhat's this new …

MySQL Cluster Connection Pooling

This guide explores how to tune and optimize the MySQL Cluster database to handle diverse workload requirements. It discusses data access patterns and how to build distribution awareness into applications, before exploring schema and query optimization, tuning of parameters and how to get the best out of the latest innovations in hardware design.

The Guide concludes with recent performance benchmarks conducted with the MySQL Cluster database, an overview of how MySQL Cluster can be integrated with other MySQL storage engines, before summarizing additional resources that will enable you to optimize MySQL Cluster performance with your applications.

Download the white paper (as always, for free) from: …

Ever wondered how fast stored routines are in MySQL? I just ran a quick micro-benchmark to compare the speed of a stored function against a "roughly equivalent" subquery. The idea -- and there may be shortcomings that are poisoning the results here, your comments welcome -- is to see how fast the SQL procedure code is at doing basically the same thing the subquery code does natively (so to speak).

Before we go further, I want to make sure you know that the queries I'm writing here are deliberately mis-optimized to force a bad execution plan. You should never use IN() subqueries the way I do, at least not in MySQL 5.1 and earlier.

I loaded the World sample database and cooked up this query:

PLAIN TEXT SQL:

1. SELECT sql_no_cache sum(ci.Population) FROM City AS ci
2.   WHERE …

This article shows how to create a MySQL-plugin that can be used to create a function which can in turn be used in stored procedures. The function will produce an integer value representing the time (to the nearest usec).

I’m working on an article for conflict detection/resolution when using MySQL Cluster asynchronous replication which requires an integer column to store a timestamp for comparison purposes. In fact, it doesn’t actually need the timestamp to represent an absolute or even a relative point in time – all it cares about is that the if the function is called twice on 2 different hosts that the 2nd call will always result in a larger number than the 1st. Obviously, in a production environment the times on the 2 hosts would need to be kept in sync.

The c code (inttime.c)

#include <mysql.h>
#include <sys/time.h>

my_bool inttime_init(UDF_INIT *initid,UDF_ARGS *args, char *message) {
  return 0;
} …

PHP 5.3 is released and after the release stress is over my mind is open for new ideas. While relaxing yesterday I thought about many things, among them was the Resultset iterator I recently discussed.

Now I wondered where to go next with this and had the idea that an individual Resultset is a child of the whole result and this might be wrapped in an Recursive Iterator. For doing so we don't implement the Iterator interface but RecursiveIterator. RecursiveIterator extends a typical Iterator with two methods: hasChildren() and getChildren(). But now we have a problem: The Iterator returned by getChildren() has to be a RecursiveIterator, too, which makes sense, in general. But I want to return a MySQLi Resultset which isn't recursive - so making this a RecursiveIterator is wrong. My solution now is to introduce yet another Iterator which goes by …

Over at phpdeveloper.org I was pointed to a blog post talking about MySQLi and stored procedures. That reminded me about a small thing I recently did: When using MySQLi's multi_query to send queries which return multiple result sets you have to use a rather unintuitive API which can certainly be improved.

Recently I sat down and cooked up a small improvement for that, being an iterator fan I, of course, had to use an iterator for that and implemented the following class:

<?php
class MySQLi_ResultsetIterator implements Iterator {
    private $mysqli;
    private $counter = 0;
    private $current = null;
    private $rewinded = false;

    public function __construct(mysqli $mysqli) {
        $this->mysqli = $mysqli;
    }
    private function freeCurrent() {
        if …