… polls: “What is the maximum number of columns in MySQL?” and “What is the minimum maximum number of columns in MySQL?”. Before you read… in the 21st century and instead wanted a modular system where the storage engines themselves owned their own metadata. This was… cannot be greater than 64kb. The bit of code in question that comes into play around the maximum number of columns is this…
Post: A case for MariaDB's Hash Joins
May 31, 2012 By Leave a Comment
…size of the hash table built on it is greater than the join_buffer_size, then multiple hash …to be performed because of the increase in the number of rows needed to be joined from supplier table…very big tables with no WHERE clause, or a WHERE clause on a non-indexed column. They also provide big …
Post: Shard-Query EC2 images available
May 11, 2011 By 2 Comments
…./worker >> /dev/null 2>&1 < /dev/null done; Where to find the images Amazon … 32bit. Requires m1.small or greater. snap-073b6e68 shard-query-demo-…offered those flights and the flight number of the flight. Some data hand updated.’; … of columns to show (click show/hide to change the columns) That the …
Post: Flexviews - part 3 - improving query performance using materialized views
April 4, 2011 By 20 Comments
…that takes 45 minutes to execute with a greater frequency than 45 minutes, even as frequently …ranking function automatically. In cases where this is not useful, simply ignore this column. It is used to…views, the last parameter is a transaction id number, which is usually obtained with flexviews.get_…
Post: Multi Range Read (MRR) in MySQL 5.6 and MariaDB 5.5
March 21, 2012 By 10 Comments
…number of these point primary key lookups will be depend on the number of rows that match the condition ‘key_column…column, pk_column FROM tbl WHERE key_column=x ORDER BY key_column (Note that secondary keys in InnoDB contain primary key columns) Buffer each pk_column… 5.5 are greater than both MySQL…
Post: Identifying the load with the help of pt-query-digest and Percona Server
December 29, 2011 By 3 Comments
…period remember to set it back to a value greater than 0, because otherwise you can have a … PARTITIONS*/ SELECT option_name, option_value FROM wp_options WHERE autoload = ‘yes’\G This is the actual part of…number of times this query was executed. Now let’s take a look at the values in the 95% column,…
Post: Joining on range? Wrong!
May 17, 2010 By 10 Comments
… columns used in joins. Let’s verify how the query performed in greater…numbers. Query matched 4103 rows, but almost 120000 were scanned. And we have proper indexes on all necessary columns…column being used by the last join. How should we understand this then? Database reads all ordered items where…
Post: How to debug long-running transactions in MySQL
March 8, 2011 By 6 Comments
…query in the processlist, and you can track down where it’s coming from in the source code. …the Host column; there you’ll see a hostname followed by a port number. That is the port number of … transaction can possibly have undo log records! The greater moral of this story is — InnoDB is designed …
