The latest from the MySQL community

After the recent update to pt-table-checksum, I’ve seen a few FAQs about it.

Q: is it still multi-threaded/parallel? A: No, that was a pile of bugs and complexity. If you need to run the tool in parallel to take advantage of powerful hardware, you can run several instances, say, one per database.

Q: what chunk size should I use? A: None, let the tool adjust itself dynamically.

Q: what if it skips a table or chunk because it’s oversized? A: this should be rare unless you have tables without any indexes; if you want to do the table in one chunk, run the tool again and specify to checksum only that table, with an appropriately large chunk size. This is one of the rare cases where you will need to specify a chunk size.

Q: what commandline options should I use after upgrading? A: It has sensible defaults for everything, and is designed to run without any options at all in most cases. If you’re upgrading from …

It might surprise you to hear this, but I had no idea whether my talks would be accepted. The committee decided on that, and neither I nor anyone else at Percona is on the committee. In any case, I’ll be giving some tutorials again this year, and two of my talks have been accepted: Measuring Scalability and Performance With TCP and Diagnosing intermittent performance problems.

This seems like an appropriate place to mention a few words about the conference organization. The number of people involved is staggering (100+). The logistics — the number of tasks, vendors, …

I’m scheduled to deliver several free MySQL webinars via Percona and ODTUG in the upcoming weeks. I hope you can join me:

• February 16 – Verifying Replication Integrity with Percona Toolkit via ODTUG.
• February 22 – EXPLAIN Demystified via Percona.
• March 14 – Optimizing MySQL Configuration via Percona.

Further Reading:

• Free webinar Wednesday: …

Are you involved with an open-source project that’s interesting to MySQL users, such as Nginx, PHPMyAdmin, Drupal, Jenkins, PHP, and so on? Percona just published the application form for dot-org groups to have a free expo hall booth in the Percona Live MySQL Conference in April. Please submit your applications now, and tell your friends about this, because a) the schedule for applying is very short, and b) space is limited.

For those of you who don’t know what this is, it’s another of the O’Reilly traditions we’re trying to continue. (We are trying very hard to make this event as close to a clone of O’Reilly’s as we can.) It’s a free table in the expo hall where people who participate in a non-commercial open source project can exhibit. I organized a Maatkit booth a few times in the past, and was always …

Schooner has a blog post showing that one node of their product beats 9 nodes of Clustrix’s in throughput. But this reduces everything to a single number, and that’s not everything that matters. If you’ve looked at Vadim’s white paper about Clustrix’s (paid-for) performance evaluation with Percona, you see there is a lot of detail about how consistent the throughput and response time are.

I’d love to see that level of details in any product comparison. A single number often isn’t enough to judge how good the performance is — fast is not the only thing that matters.

I have absolutely no doubts that a single node of Schooner’s product can run like a deer. It isn’t doing any cross-node …

http://collaborate12.ioug.org   Double Down at COLLABORATE 12- The IOUG Forum with Two Ways to Save- and a Chance to Win! The user-driven Oracle event of the year is fast-approaching, and IOUG wants you to make youreducational experience a sure bet. Between … Continue reading →

The first Central Virginia MySQL Meetup was a nice little howdy-do, and as a test flight, I think it showed that the bird can get off the ground quite nicely. So, with the generous help of our meeting host Meddius, we’re going to do it regularly on the 3rd Wednesday of every month. The next event is already scheduled — I will be talking about high availability options for MySQL.

I’m interested in having outside speakers. Anyone who’d like to come and present something MySQL-relevant, please feel free to email me, or contact me via the Meetup page with the “suggest a Meetup” feature. If you’re traveling from outside the area, the airport is CHO, and it’s about 30 minutes away. Amtrak is also …

Somebody asked for a simple comparison between a PL/SQL pass-by-value function and pass-by-reference procedure, where the procedure uses only an OUT mode parameter to return the result. This provides examples of both, but please note that a pass-by-value function can be used in SQL or PL/SQL context while a pass-by-reference procedure can only be used in another anonymous of named block PL/SQL program.

The function and procedure let you calculate the value of a number raised to a power of an exponent. The third parameter lets you convert the exponent value to an inverse value, like 2 to 1/2.

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CREATE OR REPLACE FUNCTION find_root_function
( pv_number   BINARY_DOUBLE
, pv_power    BINARY_DOUBLE
, pv_inverse  BINARY_INTEGER DEFAULT 0 ) RETURN BINARY_DOUBLE IS
 
  -- Declare local variable for return value. …

I recently wrote a post about inner and outer joins, and a couple of people asked what the difference is between USING and ON.

In a nutshell, you use ON for most things, but USING is a handy shorthand for the situation where the column names are the same.

Consider this example dataset:

mysql> select * from pets;
+---------+---------+--------+-----------+
| pets_id | animal  | name   | owners_id |
+---------+---------+--------+-----------+
|       1 | fox     | Rusty  |         2 |
|       2 | cat     | Fluffy |         2 |
|       3 | cat     | Smudge |         3 |
|       4 | cat     | Toffee |         3 |
|       5 | dog     | Pig    |         3 |
|       6 | hamster | Henry  |         1 |
|       7 | dog     | Honey  |         1 | …

I recently wrote a post about inner and outer joins, and a couple of people asked what the difference is between USING and ON.

In a nutshell, you use ON for most things, but USING is a handy shorthand for the situation where the column names are the same.

Consider this example dataset:

mysql> select * from pets;
+---------+---------+--------+-----------+
| pets_id | animal  | name   | owners_id |
+---------+---------+--------+-----------+
|       1 | fox     | Rusty  |         2 |
|       2 | cat     | Fluffy |         2 |
|       3 | cat     | Smudge |         3 |
|       4 | cat     | Toffee |         3 |
|       5 | dog     | Pig    |         3 |
|       6 | hamster | Henry  |         1 |
|       7 | dog     | Honey  |         1 | …