Glossary
A developer glossary, written to teach — built to be cited.
1.4k terms across 32 categories — definitions, examples, common mistakes and fixes. Authored under one editorial standard. Cross-linked, searchable, and openly crawled by AI agents.
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CSRF Token Handling in Fetch & Axios 3
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Memory-Mapped Files
A file mapped directly into a process's virtual address space — reads and writes go through the OS page cache rather than read()/write() syscalls, enabling fast access to large files and shared memory between processes.
2mo ago
linux advanced
Mutex vs Semaphore PHP 7.0+
A mutex allows only one thread to access a resource at a time — a semaphore controls access to a pool of N identical resources.
CWE-362
2mo ago
concurrency advanced
MySQL AUTO_INCREMENT
A column attribute that automatically assigns sequential integer IDs on INSERT — the standard primary key pattern in MySQL.
2mo ago
database beginner
MySQL charset=utf8mb4 PHP 5.1+
The correct MySQL character set for full Unicode support — including emoji and supplementary characters that the older utf8 charset cannot store.
2mo ago
php beginner
MySQL Connection Pooling PHP 5.1+
Reusing database connections across requests instead of opening and closing a new connection on every request.
2mo ago
php intermediate
MySQL Date and Time Types
DATETIME, TIMESTAMP, DATE, TIME, and YEAR — each with different ranges, timezone handling, and storage sizes.
2mo ago
database beginner
MySQL DSN (Data Source Name) PHP 5.1+
The connection string passed to PDO specifying the database driver, host, port, database name, and charset.
2mo ago
php beginner
MySQL ENUM Type
A column that accepts only predefined string values — stored efficiently as integers but with significant schema change pain.
2mo ago
database beginner
MySQL EXPLAIN
A MySQL query analysis command showing the execution plan — which indexes are used, how many rows are scanned, and where bottlenecks are.
2mo ago
database intermediate
MySQL FULLTEXT Search
A built-in MySQL search engine supporting natural language and boolean full-text queries on TEXT and VARCHAR columns.
2mo ago
database intermediate
MySQL GROUP BY and Aggregates
GROUP BY collapses rows with matching column values into one — aggregate functions (COUNT, SUM, AVG, MAX, MIN) compute values per group.
2mo ago
database intermediate
MySQL Index Types B-tree, FULLTEXT, SPATIAL, and HASH indexes — each optimised for different query patterns.
2mo ago
database intermediate
MySQL JOIN Types
INNER JOIN, LEFT JOIN, RIGHT JOIN, and CROSS JOIN — controlling which rows are included when combining tables.
2mo ago
database beginner
MySQL JSON Column Type
A native JSON storage type introduced in MySQL 5.7 that validates, indexes, and queries JSON documents with dedicated functions.
2mo ago
database intermediate
MySQL LIMIT and OFFSET Pagination
LIMIT restricts result row count; OFFSET skips rows for pagination — but OFFSET-based pagination degrades on large tables.
2mo ago
database intermediate
MySQL NULL Handling
NULL in SQL represents an unknown value — it is not zero, not empty string, and comparisons with = NULL are always false.
2mo ago
database beginner
MySQL Numeric Types
INT, BIGINT, DECIMAL, FLOAT, DOUBLE — the right type prevents overflow, precision loss, and money calculation bugs.
2mo ago
database beginner
MySQL Query Cache (Deprecated)
A server-side cache for SELECT results removed in MySQL 8.0 — it caused severe scalability issues under concurrent writes.
2mo ago
database intermediate
MySQL String Types: VARCHAR vs TEXT vs CHAR
CHAR is fixed-length, VARCHAR is variable-length up to 65,535 bytes, TEXT variants store large content — each with different indexing and storage behaviour.
2mo ago
database beginner
MySQL Subqueries
A query nested inside another — useful for filtering and deriving values, but correlated subqueries re-execute per outer row and can be O(n²).
2mo ago
database intermediate