In this section we will see SQL query which can be used to locate duplicate records in table. As explained in previous section, definition of duplicate depends upon business rules which must be used in group by clause. In following query we have used SELECT query to select all records from Contacts table.
Videos of the sessions from Drupal Camp London have started to appear on YouTube including some vox-pops style interviews from attendees. In this short interview [YouTube], MySQL co founder David Axmark gives a warning to the Drupal community. David makes a couple of observations about Drupal, drawing parallels between it and MySQL.
How to check your settings for query cache and set them up properly.
However, as we grew, scaling our existing features to accomodate more traffic turned out to be much less of an issue than adding new features.
In particular, making schema changes or adding indexes to a database with more than 10 - 20 million rows completely locks the database for hours at a time. Removing old indexes takes just as much time, and not removing them hurts performance because the database will continue to read and write to those unused blocks on every INSERT, pushing important blocks out of memory.
By temporarily dropping secondary indexes from the new table before copying the data, and then recreating them later, ALTER TABLE can take advantage of the fast index creation feature even when it has to copy the entire table.
In most cases, InnoDB is the correct choice for a Drupal site. It provides increased concurrency, enhanced performance and much more data integrity than MyISAM ever can. However, the pluggable nature of MySQL engines allows the user to "mix and match" table engines inside a single database. This allows us to consider tables whose workloads fit MyISAM more so than InnoDB. The main candidates for MyISAM in a mostly InnoDB-centric database are the search tables.
