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Displaying posts with tag: signal (reset)
What stopped MySQL? Tracing back signals sent to MySQL

Have you ever had a case where you needed to find a process which sent a HUP/KILL/TERM or other signal to your database? Let me rephrase. Did you ever have to find which process messed up your night? If so, you might want to read on. I’m going to tell you how you can find it.

Granted, on small and/or meticulously managed systems tracking down the culprit is probably not a big deal. You can likely identify your process simply by checking what processes have enough privileges to send mysqld a HUP/KILL/TERM signal. However, frequently we see cases where this may not work or the elimination process would be too tedious to execute.

We recently had a case where a process was frequently sending SIGHUPs to mysqld and the customer asked us to see if we could get rid of his annoyance. This blog is the direct result of a discussion I had with my colleague …

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A new feature just got merged into mysql-trunk, the GET DIAGNOSTICS statement.

Many people have been asking for this for a very long time, so it is worth mentioning it.

mysql> select version();
| version()    |
| 5.6.4-m6-log |
1 row in set (0.00 sec)

mysql> drop table test.no_such_table;
ERROR 1051 (42S02): Unknown table 'test.no_such_table'

Why is it important ? In short, it allows to programmatically (i.e., in SQL) inspect what happened in a SQL exception.

mysql> get diagnostics condition 1
  @p3 = MYSQL_ERRNO,
  @p4 = SCHEMA_NAME,
  @p5 = TABLE_NAME;

Query OK, 0 rows affected (0.00 sec)

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Re-implementing udf_init_error in MySQL 5.5 and up

To whom it may concern -

Today, I received an email from a user of the udf_init_error UDF (which resides in the lib_mysqludf_udf library). The purpose of this UDF is to generate an error condition, which can be used to abruptly terminate a trigger or stored procedure. As such it is a workaround for bug #11661. This is all described extensively in my now ancient article here.

The user wrote me because of a problem experienced in MySQL 5.5: ...calling

select …
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Validating MySQL data entry with triggers: A quick look at the SIGNAL syntax

The latest MySQL 5.5 milestone release offers support for an ANSI/ISO standard feature called the SIGNAL syntax. You can use this syntax inside stored routines (including triggers) to raise an error condition which can be used to invoke specific error handling, or otherwise abort the stored routine. In addition, you can use the SIGNAL syntax to convey information about what went wrong, which may be used by the caller to handle the error.

I have written about MySQL data entry validation procedures in the past. At the time, MySQL did not support any proper means to raise an error condition inside a stored routine, and …

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Getting started with MySQL 5.5

Some time go, we announced a new release model for MySQL. As all new things, it had some initial hiccups (with MySQL 5.4 we were still getting acquainted with the new model), but now it seems to be in full swing.
By the time you read these lines, MySQL 5.5 will be available. If the mirrors aren't seeded yet, the impatient can compile and use the new version from the launchpad source tree..

OverviewWhat's this new …

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Community at work - SIGNAL

Long time ago, I saw a blog post by Jorge Bernal, with a simple implementation of SIGNAL for MySQL stored procedures. If you have ever tried to write MySQL stored procedures, you know how dearly missed is this feature.
I discussed this feature internally, and everyone told me "don't bother, we're going to implement SIGNAL in MySQL 6.1". And indeed, the full implementation for SIGNAL and RESIGNAL is in the roadmap.

What does that mean? Should we wait two …

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Showing entries 1 to 6