Recently we were puzzled by question how query_cache works with column level privileges. The question was appeared as we discovered function query_cache_send_result_to_client is called before real parsing of query, so at the moment of execution the query_cache is not able to know which columns are accessed.
Looking into source code I found out that in […]
During last couple of months I had number of consulting projects with MySQL Query Cache being source of serious problems. One would see queries both for MyISAM and Innodb tables mysteriously stalling for few seconds with “NULL” in State column.
These could be troubleshooted to waiting on Query Cache which at […]
While there is no magic bullet for MySQL 5.7 database tuning, there are a few areas that can be focused on upfront that can dramatically improve the performance of your MySQL installation. While much information has been published on this topic over the years, I wanted to break down some of the more critical […]
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Multiplexing Background
Historically it’s a technique used in networking to integrate multiple analog and digital signals via a shared medium. The goal of multiplexing over the network was to enable signals to be transmitted more efficiently for a given communication channel, thus achieving cost efficiency.
Since the term Multiplexing comes from telecommunications, the industry has heavily […]
Recently I had a customer where every single query was running in a transaction, as well as even the simplest selects. Unfortunately, this is not unique and many connectors like Java love to do that.
In their case, the Java connector changed autocommit=off for the connection itself at the beginning, and as these were permanent […]
