MySQL Concurrency : Locking and Transactions for MySQL Developers and DBAs

Table of Contents About the Author About the Technical Reviewer Acknowledgments Introduction Chapter 1: Introduction Why Are Locks Needed? Lock Levels Locks and Transactions Examples Prerequisites for the concurrency_book.generate Module Installing the concurrency_book.generate Module Getting Information Loading Test Data Executing a Workload Test Data: The world Schema Schema Installation Test Data: The sakila Schema Schema Installation Test Data: The employees Schema Schema Installation Summary Chapter 2: Monitoring Locks and Mutexes The Performance Schema Metadata and Table Locks Data Locks Synchronization Waits Statement and Error Tables The sys Schema Status Counters and InnoDB Metrics Querying the Data Configuring the InnoDB Metrics InnoDB Lock Monitor and Deadlock Logging InnoDB Mutexes and Semaphores Summary Chapter 3: Monitoring InnoDB Transactions Information Schema INNODB_TRX InnoDB Monitor INNODB_METRICS and sys.metrics Summary Chapter 4: Transactions in the Performance Schema Transaction Events and Their Statements Transaction Summary Tables Summary Chapter 5: Lock Access Levels Shared Locks Exclusive Locks Intention Locks Lock Compatibility Summary Chapter 6: High-Level Lock Types User-Level Locks Flush Locks Metadata Locks Explicit Table Locks Implicit Table Locks Backup Locks Log Locks Summary Chapter 7: InnoDB Locks Record Locks and Next-Key Locks Gap Locks Predicate and Page Locks Insert Intention Locks Auto-Increment Locks Mutexes and RW-Lock Semaphores Summary Chapter 8: Working with Lock Conflicts Contention-Aware Transaction Scheduling (CATS) InnoDB Data Lock Compatibility Metadata and Backup Lock Wait Timeouts InnoDB Lock Wait Timeouts Deadlocks InnoDB Mutex and Semaphore Waits Summary Chapter 9: Reducing Locking Issues Transaction Size and Age Indexes Record Access order Transaction Isolation Levels Configuration Resource Partitioning Disabling the InnoDB Adaptive Hash Index Reducing Priority of Metadata Write Locks Preemptive Locking Summary Chapter 10: Indexes and Foreign Keys Indexes Primary vs. Secondary Indexes Ascending vs. Descending Indexes Unique Indexes Foreign Keys DML Statement DDL Statement Summary Chapter 11: Transactions Transactions and ACID Atomicity Consistency Isolation Durability Impact of Transactions Locks Undo Logs Group Commit Summary Chapter 12: Transaction Isolation Levels Serializable Repeatable Read Read Committed Read Uncommitted Summary Chapter 13: Case Study: Flush Locks The Symptoms The Cause The Setup The Investigation The Solution The Prevention Summary Chapter 14: Case Study: Metadata and Schema Locks The Symptoms The Cause The Setup The Investigation The Solution The Prevention Summary Chapter 15: Case Study: Record-Level Locks The Symptoms The Cause The Setup The Investigation The Solution The Prevention Summary Chapter 16: Case Study: Deadlocks The Symptoms The Cause The Setup The Investigation The Solution The Prevention Summary Chapter 17: Case Study: Foreign Keys The Setup The Discussion Errors and High-Level Monitoring Lock Metrics Metadata Lock Contention InnoDB Lock Contention The Solution and Prevention Summary Chapter 18: Case Study: Semaphores The Symptoms The Cause The Setup The Investigation The InnoDB RW-Lock Metrics InnoDB Monitor and Mutex Monitor Determining the Workload The Solution and Prevention Disabling the Adaptive Hash Index Increase the Number of Hash Index Parts Other Solutions Summary Appendix A: References Tables and Views Lock Information Metadata Object Types Metadata Lock Types Transaction Information Statement Information Wait Information Table I/O Information File I/O Information Error Information Status Variables and InnoDB Metrics InnoDB Monitor Sections Appendix B: MySQL Shell Module Prerequisites Installation The help() and show() Methods Loading Test Data Executing a Workload Module Structure Library Files innodb_buffer_pool.py innodb_monitor.py innodb_mutex.py load.py log.py metrics.py query.py util.py workloads.py Workloads Directory Defining Workloads Global Keys Queries and Completions Investigations Summary Index Know how locks work in MySQL and how they relate to transactions. This book explains the major role that locks play in database systems, showing how locks are essential in allowing high-concurrency workloads. You will learn about lock access levels and lock granularities from the user level as well as table locks to record and gap locks. Most importantly, the book covers troubleshooting techniques when locking becomes a pain point. Several of the lock types in MySQL have a duration of a transaction. For this reason, it is important to understand how transactions work. This book covers the basics of transactions as well as transaction isolation levels and how they affect locking. The book is meant to be your go-to resource for solving locking contention and similar problems in high-performance MySQL database applications. Detecting locking issues when they occur is the first key to resolving such issues. MySQL Concurrency provides techniques for detecting locking issues such as contention. The book shows how to analyze locks that are causing contention to see why those locks are in place. A collection of six comprehensive case studies combine locking and transactional theory with realistic lock conflicts. The case studies walk you through the symptoms to look for in order to identify which issue you are facing, the cause of the conflict, its analysis, solution, and how to prevent the issue in the future. What You Will LearnUnderstand which lock types exist in MySQL and how they are usedChoose the best transaction isolation level for a given transactionDetect and analyze lock contention when it occursReduce locking issues in your applicationsResolve deadlocks between transactionsResolve InnoDB record-level locking issuesResolve issues from metadata and schema locksWho This Book Is ForDatabase administrators and SQL developers who are familiar with MySQL and want to gain a better understanding of locking and transactions as well as how to work with them. While some experience with MySQL is required, no prior knowledge of locks and transactions is needed. Know how locks work in MySQL and how they relate to transactions. This book explains the major role that locks play in database systems, showing how locks are essential in allowing high-concurrency workloads. You will learn about lock access levels and lock granularities from the user level as well as table locks to record and gap locks. Most importantly, the book covers troubleshooting techniques when locking becomes a pain point. Several of the lock types in MySQL have a duration of a transaction. For this reason, it is important to understand how transactions work. This book covers the basics of transactions as well as transaction isolation levels and how they affect locking. The book is meant to be your go-to resource for solving locking contention and similar problems in high-performance MySQL database applications. Detecting locking issues when they occur is the first key to resolving such issues. MySQL Concurrency provides techniques for detecting locking issues such as contention. The book shows how to analyze locks that are causing contention to see why those locks are in place. A collection of six comprehensive case studies combine locking and transactional theory with realistic lock conflicts. The case studies walk you through the symptoms to look for in order to identify which issue you are facing, the cause of the conflict, its analysis, solution, and how to prevent the issue in the future. You will: Understand which lock types exist in MySQL and how they are used Choose the best transaction isolation level for a given transaction Detect and analyze lock contention when it occurs Reduce locking issues in your applications Resolve deadlocks between transactions Resolve InnoDB record-level locking issues Resolve issues from metadata and schema locks