Emergency

Search Results for: active transactions

Queries Active vs Transactions Active

What is wrong here (the part of SHOW INNODB STATUS): ————– ROW OPERATIONS ————– 8 queries inside InnoDB, 9 queries in queue 100 read views open inside InnoDB It is relationship between queries active – …

Read More
 

On TokuMX (and MongoDB) Replication and Transactions

In my last post, I describe the differences between a TokuMX oplog entry and a MongoDB oplog entry. One reason why the entries are so different is that TokuMX supports multi-statement and multi-document transactions. In …

Read More
 

Interactive Debugging of Transaction Conflicts with TokuDB

I am developing a concurrent application that uses TokuDB to store its database. Sometimes, one of my SQL statements returns with a ‘lock wait timeout exceeded’ error. How do I identify the cause of this …

Read More
 

ACTIVE with Locks – Now thats a problem !

One of item I always look at SHOW ENGINE INNODB STATUS to see if there are any transactions spending very long time in ACTIVE state. In the perfect world if you’re running online system you …

Read More
 

MySQL’s INNODB_METRICS table: How much is the overhead?

Starting with MySQL 5.6 there is an INNODB_METRICS table available in INFORMATION_SCHEMA which contains some additional information than provided in the SHOW GLOBAL STATUS output – yet might be more lightweight than PERFORMANCE_SCHEMA. Too bad …

Read More
 

10 MySQL settings to tune after installation

When we are hired for a MySQL performance audit, we are expected to review the MySQL configuration and to suggest improvements. Many people are surprised because in most cases, we only suggest to change a …

Read More
 

TokuDB Hot Backup – Part 2

In my last post, I discussed the existing backup solutions for MySQL.  At the end I briefly discussed why the backup solutions for InnoDB do not apply to TokuDB.  Now I’m going to outline the …

Read More
 

kernel_mutex problem. Or double throughput with single variable

Problem with kernel_mutex in MySQL 5.1 and MySQL 5.5 is known: Bug report. In fact in MySQL 5.6 there are some fixes that suppose to provide a solution, but MySQL 5.6 yet has long way …

Read More
 

MySQL Error Message Nonsenses

What MySQL honestly was never good at is giving good helpful error messages. Start with basics for example – The error message in case of syntax error gives you information about tokens near by but …

Read More
 

SHOW INNODB STATUS walk through

Many people asked me to publish a walk through SHOW INNODB STATUS output, showing what you can learn from SHOW INNODB STATUS output and how to use this info to improve MySQL Performance. To start …

Read More