June 19, 2013

Post: MySQL Query Patterns, Optimized - Webinar questions followup

index.  But the result was that it created a temporary table to count the movies per production year for each kind_id. It was morecolumns.  It turned out this solution was 150x faster for this case, so your suggestion is a good one! Thanks again for

Post: The Optimization That (Often) Isn't: Index Merge Intersection

for a given SELECT would show N possible index choices but only one index actually used. To some extent, MySQLmore than one way to do it. Otherwise known as beware the law of unintended consequences. Sometimes we have to sacrifice “elegance” (IMHO, index

Post: InnoDB Full-text Search in MySQL 5.6 (part 1)

indexes with InnoDB in the same ALTER TABLE statement, but it’s not possible to CREATE more than one at a time. If you try it, this is what happens: mysql> alter table dir_test_innodb ADD FULLTEXT KEY

Post: Shard-Query EC2 images available

for all configurations of more than onewas discussed in the comments of the last post. ICE does not have any indexes (not even primary keyscolumn store performs about 8x-10x better than a row store for queries which access a significant amount of data. One big reason for

Post: MySQL 5.6.10 Optimizer Limitations: Index Condition Pushdown

than the same “SELECT one_indexed_column” query in MySQL 5.6.10. This turned into a really nice exercise formore background information. My buffer pool was big enough to hold the whole database (data and indexes fit completely in memory). Also, I was

Post: Troubleshooting MySQL Memory Usage

key_buffer_size etc, you have reasonable amount of connections but yet MySQL takes much more memory thanMySQL memory consumption plotted. I use “VSZ” columnsone by one so it is easier to understand which of the applications were responsible forINDEX_LENGTH: 0 CREATE

Post: A case for MariaDB's Hash Joins

than the join_buffer_size, then multiple hash tables would be created. Forindexed column The SQL used for this test together with its EXPLAIN output as returned by MySQLfor each distinct key value. Also the joining key in this test case D is PK in one

Post: Multi Range Read (MRR) in MySQL 5.6 and MariaDB 5.5

index optimization is not used), then primary key lookups have to be performed for each secondary key entry fetched. This means that secondary key lookups for columnmore rows than MySQL 5.5, as can be seen by the numbers reported for the status counter Innodb_rows_read. While MySQL

Post: High-Performance Click Analysis with MySQL

… last time I was involved with…indexes other than the primary key, we can shrink the primary key‘s width: create…? We dropped one column, and …more. Finally, PostgreSQL is clearly better for some workloads out-of-the-box than MySQL is, especially for more complex queries. Percona is not tied to MySQL

Post: On Character Sets and Disappearing Tables

key will reference a column with a mismatched data type. For instance, if we have these two tables: CREATEone more reason (as if you needed any more) to keep good backups that are tested regularly. Tested under MySQL