MySQL Histograms: When MySQL Ignores Them

MySQL can ignore histograms in the query optimizer when it determines that using the histograms would not provide any benefit to the query execution plan. This can occur in several cases, including: Why MySQL ignores […]

MySQL Mutex Contention: Troubleshooting Guide

Mutex contention occurs in MySQL when multiple threads attempt to access a shared resource, such as a data structure or a system resource, simultaneously. Because only one thread can access the resource at a time, […]

PostgreSQL 16 Cache Buffer Chains Demystified

Cache Buffer Chains (CBC) is a mechanism used by the PostgreSQL storage engine to manage the buffer cache and minimize the amount of disk I/O. The buffer cache is a region of memory that is […]

How to use PgBouncer for implementing connection pooling in PostgreSQL?

PgBouncer is a lightweight connection pooler for PostgreSQL. It is used to reduce the overhead of establishing a new connection to a PostgreSQL database for each client request. By pooling connections, PgBouncer can handle a […]

PostgreSQL Internals – Hacking PostgreSQL Parser

The source code for the PostgreSQL LALR(1) parser is written in C and can be found in the PostgreSQL source code repository. The main components of the parser are: To understand how the parser works, […]

PostgreSQL Freelists: Internals and Implementation

The freelists in PostgreSQL are implemented as a linked list of pages. Each page is a unit of disk space that is managed by the freelist, and its size is determined by the block size […]

PostgreSQL CPU Cache Buffers Chains Latch: How to Monitor It

The CPU Cache Buffers Chains Latch in PostgreSQL is a synchronization mechanism that protects the buffer cache data structure. The buffer cache is a pool of memory used by PostgreSQL to cache disk blocks that […]

InnoDB MVCC: How It Is Implemented

Multiversion Concurrency Control (MVCC) is a mechanism that is used by InnoDB, the default storage engine in MySQL, to provide transactional consistency and support for concurrent access to the same data. In InnoDB, MVCC is […]

MySQL 8 Biased Joins: How They Influence Query Performance

A biased join in MySQL 8 can have a significant impact on query performance. A biased join occurs when the query optimizer makes a decision to use a particular index or join type based on […]

MySQL Histograms: What They Are and How They Are Used

In MySQL, histograms are statistical representations of the distribution of data in a table column. They provide information about the distribution of values in a column, which can be used by the query optimizer to […]

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