The article explains why using the KEYS command on large Redis datasets can cause service blockage and demonstrates how the SCAN command with MATCH and COUNT options provides a non‑blocking, incremental way to list keys, including syntax and practical examples.
This article explains the importance of idempotent operations in backend systems, defines the concept, and presents practical techniques such as unique indexes, token mechanisms, pessimistic and optimistic locking, distributed locks, state‑machine design, and API patterns, complete with code snippets and diagrams.
This guide walks you through setting up the open‑source MySQL Monitor tool, covering environment preparation, installation, database schema import, host configuration, alert channel setup (email and WeChat), cron scheduling, and accessing the monitoring pages, all with a clean Chinese interface.
This article provides a comprehensive overview of Redis, explaining its core data structures, caching use cases, persistence mechanisms, high‑availability features like Sentinel and replication, clustering for horizontal scaling, and client‑side capabilities such as transactions, Lua scripting, pipelining, and distributed locks.
This comprehensive guide covers fundamental SQL Server operations such as creating databases, tables, indexes, and views, advanced techniques like set operators, subqueries, and linked servers, plus step‑by‑step instructions for replication, backup, compression, and automated synchronization using stored procedures and SQL Agent jobs.
This guide walks through installing Zabbix 4.4.0 on CentOS 7, configuring PostgreSQL, adding the TimescaleDB time‑series extension, setting up the Zabbix database, and tuning Linux, Nginx, and PHP so the monitoring platform runs smoothly with high‑performance time‑series storage.
This article explains how to use MySQL's EXPLAIN command, describes each column in its output—including id, select_type, table, type, possible_keys, key, key_len, ref, rows, filtered, and Extra—provides syntax examples, discusses join type rankings, and outlines the command's limitations for query performance analysis.
This weekly newsletter summarizes the latest DBLE, DTLE, and TXLE open‑source middleware updates, including bug fixes, new features, community Q&A, documentation releases, upcoming releases, and links to related videos and articles for developers.
This article explains how to quickly set up MySQL (as well as MariaDB and Percona) inside Docker containers, covering official images, running the latest version, connecting to the server, managing container lifecycle, passing server options, and handling multiple or specific MySQL versions.
This article examines common MySQL performance pitfalls such as inefficient LIMIT usage, implicit type conversion, suboptimal joins, mixed sorting, and unpushed predicates, and demonstrates eight practical rewriting techniques—including using max values, JOINs, WITH clauses, and early range reduction—to dramatically accelerate query execution.
This article introduces Xiaomi's open‑source SOAR tool, explains how to download and install the binary or source versions, walks through quick‑start commands, details key YAML configuration options and output formats, and describes four typical usage scenarios for SQL optimization and rewriting.
This article explains how Redis manages key expiration using EXPIRE, PEXPIRE, EXPIREAT, and PEXPIREAT commands, details the internal expires dictionary, demonstrates code examples for setting, retrieving, and removing TTL, and discusses the lazy and periodic deletion strategies along with their impact on persistence and replication.
This article explains how to design and implement a high‑frequency like/unlike feature for large social platforms using Spring Cloud, Redis caching, MySQL persistence, and Quartz scheduled jobs, covering Redis setup, data modeling, service interfaces, database schema, and periodic data synchronization.
The article explains the differences between cache and buffer, how Oracle’s log buffer and data buffer cache interact with various storage‑level caches, and why write‑back, battery‑backed caches, RAID and disk cache settings are crucial for maintaining data consistency during power loss.
This article explains MySQL date‑time data types, compares DATETIME and TIMESTAMP, shows how to map them to Java types, provides SQL examples, and demonstrates several methods for timezone conversion between MySQL and Java applications.
This article chronicles Alipay’s engineering journey from 2009 to the present, detailing how its distributed middleware, database sharding, load‑balancing, LDC, OceanBase, cloud‑native Service Mesh, big‑data and blockchain technologies have been continuously refined to support ever‑growing Double 11 transaction volumes.
This article explains how IO and CPU bottlenecks increase active database connections, describes horizontal and vertical sharding techniques, outlines practical steps and tools for implementing sharding, and discusses common challenges such as non‑partition key queries and expansion strategies.
This tutorial walks through setting up the Python happybase library, installing JPype for Java integration, and demonstrates end‑to‑end code examples for connecting to an HBase Thrift server, generating row keys via Java utilities, querying data, and handling type conversions.
The 2019 Data Technology Carnival in Beijing featured a presentation by iKesheng on how a private MySQL‑based RDS solution was designed, deployed, and operated in a state‑owned bank, covering node integration, operational standards, high‑availability scenarios, and multi‑site disaster recovery.
This guide introduces a set of scripts for installing MySQL 8.0, configuring master‑slave replication and group replication, detailing required files, command usage, repository location, and essential configuration notes for a three‑node deployment.
This guide explains how to create automated backup plans for MySQL and MariaDB databases on Jelastic PaaS, covering script configuration, cron scheduling, remote storage options, and restoring backups through phpMyAdmin, ensuring data safety and easy recovery.
This article explains the meaning of NULL in SQL, distinguishes the two conceptual types of unknown and not‑applicable, describes three‑valued logic, shows why IS NULL must be used instead of = NULL, and warns about pitfalls such as NOT IN with NULL and improper CASE expressions.
This article explains InfluxDB's Continuous Queries feature, covering configuration settings, basic and advanced syntax, execution timing, data range handling, result storage, and the use of RESAMPLE clauses with practical examples and code snippets.
This article explains why MySQL uses B+‑tree indexes by tracing the evolution from binary search trees through balanced trees and B‑trees, detailing the structure of clustered and non‑clustered indexes in InnoDB and illustrating how data is searched using these indexes.
This article demonstrates how to leverage uiautomator1.0 for Android automation by creating a shell‑based Context, accessing PackageManager, managing SQLite databases, monitoring app activities and processes, and implementing Chinese text input through AccessibilityNodeInfo.
This guide explains InfluxDB’s schemaless data types, best practices for designing tag‑and‑field schemas, and how to choose and configure its in‑memory or TSI indexes, including key parameters such as max‑series‑per‑database and max‑values‑per‑tag for optimal performance.
A detailed case study shows how a DELETE statement executed inside a MySQL stored procedure can switch binlog format to ROW, causing billions of bitmap operations on a partitioned table and resulting in severe master‑slave replication delay, and presents three practical solutions.
KeyDB is a high‑performance, multithreaded fork of Redis that retains full Redis compatibility while delivering up to twice the query throughput and 60 % lower latency, and the article explains its thread model, connection management, fastlock mechanism, and active‑replica features in detail.
This article introduces JDTX, a novel distributed transaction middleware that combines ACID guarantees, high performance, and 1PC architecture, explains its design principles, compares two‑phase commit with flexible transactions, details its MVCC and WAL implementation, and outlines integration with Apache ShardingSphere and future roadmap.
The article explains how MySQL 8.0 introduced the instant algorithm for adding columns, compares it with older copy and inplace‑rebuild methods, shows usage examples, performance test results, and outlines the restrictions and version differences of this fast DDL operation.
From a 2009 mandate to eliminate minicomputers to a 2019 TPC‑C world‑record, Alibaba’s decade‑long “de‑IOE” project forged OceanBase into a fully self‑developed, Oracle‑compatible database, delivering flexible architecture, talent growth, and massive cost savings while reshaping China’s IT landscape.
This article analyzes the MySQL slow query log in Percona 5.7, explaining how timestamps, execution time, lock time, and various log fields are derived from the source code, and clarifies the meaning of each output component for accurate performance debugging.
This article provides a comprehensive guide to Redis persistence mechanisms, covering the internal database structure, detailed operations of RDB snapshotting and AOF command logging, their configurations, advantages, drawbacks, hybrid persistence, and practical strategy recommendations for various deployment scenarios.
The article explains a 14‑hour discrepancy between MySQL's created_time and recovery_time timestamps, analyzes JVM and driver timezone settings, traces MyBatis and MySQL driver conversions, and provides practical fixes by adjusting MySQL server and JDBC URL timezones.
This article explains the structure and purpose of the MySQL slave_relay_log_info table, how relay log positions are persisted and synchronized, the role of master_auto_position and GTID, and the mechanisms of relay_log_recovery to ensure reliable replication after crashes.
Maoyan Entertainment created the “Tangtu” mini‑program operation tool with WeChat Cloud Development, letting operations and product managers visually design, edit and publish holiday activities via cloud storage, database and functions, cutting staff from three to one, slashing development time and cost while highlighting the need for explicit environment variables and careful migration from traditional MySQL services.
This article explains how to identify slow MySQL queries using the slow‑query log and SHOW PROCESSLIST, then demonstrates how to analyze their execution plans with EXPLAIN, covering key fields, common values, and practical examples for effective performance optimization.
This article provides an in‑depth overview of MongoDB’s aggregation framework, explaining the concepts of pipelines and stages such as $match, $group, $project, $lookup, $unwind, and $out, and includes practical code examples, syntax details, and comparisons to SQL aggregation.
PostgreSQL 12 brings major enhancements—including up to 40% faster queries on large datasets, improved indexing, partitioning, JSON path queries, generated columns, pluggable table access methods, stronger authentication, and built‑in JIT compilation—while also adding better localization, multi‑constraint authorization, and convenient maintenance commands.
This article explains how the apply‑log‑only option in Percona XtraBackup affects MySQL restoration, illustrates the risk of data inconsistency when the option is omitted, and provides guidance on correctly using the parameter during full and incremental backup recovery to ensure complete transaction replay.
A bug was discovered where a user's VIP expiration date could not extend beyond a specific day in 2038 because the timestamp was stored in a signed INT column, whose maximum value (2147483647) corresponds to 2038‑01‑19 11:14:07, causing the system to fail to save later dates.
This article explains how to calculate cumulative daily user totals in MySQL using user-defined variables, demonstrates the necessary SQL queries, compares them with a Java‑style algorithm, and highlights important considerations such as variable initialization and practical pitfalls.
An in‑depth exploration of Oracle 12c’s multitenant architecture explains key concepts, analyzes a real‑world backup failure, and provides a comprehensive, step‑by‑step RMAN procedure—including control file handling, datafile restoration, and selective tablespace skipping—to reliably recover pluggable databases.
This article provides a comprehensive MySQL replication FAQ covering cross‑OS and hardware compatibility, master‑slave connection behavior, monitoring lag, forcing master pause, bidirectional replication considerations, performance improvements, high‑availability setups, and how to exclude GRANT/REVOKE statements from replication.
This article examines Ctrip's approach to achieving multi‑region, bidirectional Redis replication by employing CRDT techniques and strong eventual consistency to overcome the limitations of single‑directional sync, network partitions, and data‑conflict challenges in distributed database systems.
The article provides a comprehensive overview of DBLE version 2.19.07.0, including project background, new features, enhanced data import/export methods, updated show commands, protocol extensions, a full translated release‑notes list, bug‑fix details, and compatibility changes for this distributed database middleware.
This article outlines the design of a unified multi‑account login system, covering self‑built phone‑number authentication, optimized password‑less login, third‑party integrations, database schema separation, and a one‑click carrier‑based login to improve user experience and scalability.
This article explains the fundamentals of Multi-Version Concurrency Control (MVCC), compares its implementation in PostgreSQL and InnoDB, and highlights key differences in version storage, transaction handling, vacuuming, and index updates.
The iKesheng community’s weekly roundup shares upcoming events like the DBLE Beijing meet‑up, free Mycat diagnosis services, detailed DBLE and DTLE weekly reports, and technical articles on global lock detection, slave data search, and hash algorithm choices, offering valuable insights for database professionals.
The article distills years of Java backend experience into a concise checklist, showing how to replace JVM‑local locks with distributed locks, move thread‑blocked work to reliable message queues, model workflows with finite‑state machines, choose suitable inter‑service protocols, and always paginate queries to avoid memory and consistency problems.
This article reviews various distributed ID generation strategies—including database auto‑increment tables, dual‑master MySQL setups, segment allocation, the Snowflake algorithm, and Redis INCR—detailing their designs, SQL examples, scalability trade‑offs, and open‑source implementations.
This article compiles essential Redis interview questions covering its advantages over Memcached, performance pitfalls, data structures, persistence options, clustering, scaling strategies, and practical usage patterns such as distributed locks and asynchronous queues, providing concise answers and best‑practice recommendations for each topic.
This guide explains how to configure replication from a MySQL 8.0 master to a MySQL 5.7 slave, covering supported version combinations, character‑set adjustments, authentication plugin changes, user creation, CHANGE MASTER commands, status verification, quick testing, and common pitfalls when using newer MySQL features.
The article explains why HBase client connections should not be pooled, describes common misuse patterns, and details how the heavyweight, thread‑safe Connection object internally manages connections to HMaster, RegionServers, and ZooKeeper, recommending a single shared Connection per application.
The August 17 “Mini‑Program·Cloud Development” salon explained how Tencent Cloud’s server‑less BaaS/FaaS platform lets WeChat mini‑game developers replace traditional H5 back‑ends with lightweight cloud functions, databases and CDN storage, cutting development time from hours to minutes, while supporting real‑time sync, token management, and future SDK expansions.
This article presents nineteen practical MySQL optimization methods—including using EXPLAIN, limiting IN clause size, specifying columns in SELECT, proper use of LIMIT, avoiding costly ORDER BY RAND(), choosing between IN and EXISTS, leveraging full‑text indexes, and applying join and index best practices—to improve query performance and reduce resource consumption.
This guide explains how to solve Selenium‑Java cookie expiration by fetching the latest user token from a MySQL database and inserting only the essential MyName and User_token_Session cookies before refreshing the browser session.
This article analyzes the performance bottlenecks of a MongoDB‑based CMDB under high write concurrency, explains index structures and storage, demonstrates how to identify and eliminate full‑table scans and redundant multikey indexes, and shows the resulting reduction in slow‑log volume and CPU usage.
This article explains the storage capacity of InnoDB B+‑tree indexes by detailing page size, record size, pointer calculations, tree height effects, and real‑world verification using page‑level metadata, showing that a typical B+‑tree can hold tens of millions of rows with only 1‑3 I/O operations.
This article introduces Redis's fundamental and advanced data structures, explains how each is represented internally, and provides detailed examples of essential commands such as KEYS, EXISTS, DEL, EXPIRE, TTL, and TYPE, highlighting their usage, complexity, and best‑practice considerations.
The article compares MySQL 8.0 and MySQL 5.7 memory usage on a 1 GB VM, showing that MySQL 8.0 consumes significantly more resident and swap memory despite similar lightweight workloads, and provides the test configuration and observations for developers.
This article explains how to implement order number generation services by first using a simple auto‑increment‑based database table and then a more sophisticated segment‑allocation method that reduces database load, with detailed SQL and Java code examples and transaction‑handling advice.
This weekly digest highlights the August MySQL ranking surge, Percona XtraBackup 8.0.7 features, free Mycat diagnostic support, DBLE and DTLE weekly reports, and several in‑depth technical articles covering MySQL cloning, group replication, charset performance, ZooKeeper deployment, and InnoDB index construction.
The article details Redis 6’s new multithreaded I/O feature—motivated by network‑I/O bottlenecks, implemented with lock‑free pending‑read queues that offload reads, writes, and protocol parsing to worker threads while keeping command execution single‑threaded—and demonstrates through a simple benchmark that using four I/O threads roughly doubles GET/SET throughput compared with Redis 5.
Since MySQL 5.7 InnoDB builds secondary indexes using a bottom‑up, sorted‑index approach, the article explains the three build phases, presents a step‑by‑step B‑tree construction example with SQL code, and discusses the innodb_fill_factor setting, its impact, advantages, and drawbacks.
Starting with MySQL 8.0.17, Group Replication introduces patch‑level version compatibility policies that govern primary‑member election, write‑ability, donor selection, and upgrade procedures for mixed‑version clusters, ensuring safe operation during rolling upgrades and multi‑primary mode transitions.
This article explains how MySQL's case‑sensitivity differs between Windows and Linux, why table‑name mismatches cause errors, and how to use the lower_case_file_system and lower_case_table_names variables to control behavior, with practical examples and migration tips.
The article demonstrates a simple Java ThreadTest class that enables concurrent database updates during Android UIAutomator and Selenium‑Java test cases, showing how to control execution with key flags, integrate the thread into test methods, and optionally use join() to avoid exceptions.
This article explains the two‑layer architecture of NewLife.Redis, demonstrates basic and advanced usage with code examples, shares stress‑test results achieving hundreds of thousands of operations per second, and provides practical tips and FAQs for high‑performance Redis deployments.
This article explores the challenges of building layered, flexible database queries in Go, compares GORM, sqlx, and squirrel, and proposes a custom, option‑based query‑builder pattern that stays idiomatic and extensible for complex search scenarios.
This article introduces the global data replication market, explains synchronous and asynchronous replication, and details five typical replication techniques—host‑based, application/middleware‑based, database‑based, storage‑gateway‑based, and storage‑media‑based—highlighting their principles, advantages, and trade‑offs for disaster‑recovery planning.
This article presents practical MySQL performance tricks—including smarter LIMIT usage, avoiding implicit type conversion, rewriting UPDATE/DELETE with JOIN, handling mixed ordering, replacing EXISTS with JOIN, pushing down conditions, narrowing result sets early, and leveraging WITH clauses—to dramatically reduce query execution times.
The article explains how using the KEYS command on millions of Redis keys blocks the single‑threaded server, causing outages, and demonstrates how the incremental SCAN command with cursor, MATCH, and COUNT options provides a safe, non‑blocking way to iterate large keyspaces.
This guide provides step‑by‑step Oracle commands for creating and dropping databases, performing full and selective backups, restoring data locally or remotely, managing tables—including creation, deletion, renaming, column alterations, primary keys, indexes, and views—as well as querying, inserting, updating, deleting, and copying data efficiently.
This article explains how MySQL's LATERAL join and recursive CTE can be used to compute the number of direct and indirect reports for each employee, demonstrating lateral external references, non‑lateral references, query execution details, and EXPLAIN output in MySQL 8.0.14 and later.
The article outlines comprehensive MySQL database standards covering naming conventions, table and column design, index strategies, SQL development practices, and operational guidelines to improve performance, maintainability, and security, including recommendations on data types, character sets, reserved fields, binary data storage, and safe query patterns.
This article explains how to replace the nth occurrence of a substring in MySQL, comparing a custom stored function, an export‑sed‑import workflow, and the built‑in REGEXP_REPLACE and REGEXP_INSTR functions introduced in MySQL 8.0, with examples for both ASCII and multibyte strings.
The article describes a Java performance testing framework that was refactored from a request‑based to a method‑based design, introducing a ThreadBase class and specialized adapters for HTTP requests, database queries, and concurrent execution, and discusses the advantages of code‑based concurrency and Groovy.
MySQL 8.0.17 introduces server cloning via MySQL Shell, multi‑value indexes for JSON arrays, enhanced JSON schema validation, optimizer and Volcano iterator upgrades, new collations, replication and routing enhancements, plus numerous bug fixes and deprecations, all detailed in the official release notes.
A developer recounts how a misconfigured production environment led to the accidental deletion of both content and user databases, the frantic scramble to diagnose the issue, the discovery of a backup oversight, and the hard‑earned lessons on backups, testing, and authentication security.
This comprehensive guide covers MySQL basics, including the definition of MySQL, transaction concepts and ACID properties, isolation levels, common concurrency issues, index structures and usage, storage engine differences, lock mechanisms, and practical techniques for optimizing large tables and improving performance.
The article traces Taobao's backend architecture evolution—from a single‑machine setup through caching, load balancing, database sharding, microservices, containerization, and cloud deployment—illustrating the technologies and design principles needed to scale from hundreds to tens of millions of concurrent users.
This weekly digest summarizes the latest MySQL 8.0.17 enhancements, Redis 6's new RESP3 protocol, free Mycat diagnostics, DBLE and DTLE weekly reports, original technical articles on MySQL fragmentation, dynamic permissions and TempTable engine, plus details of the upcoming Shanghai 3306π meetup.
This article explains Redis string basics, its mutable SDS implementation, common commands, internal memory layout, and the three encoding formats (int, embstr, raw) that determine how strings are stored and optimized in the database.
The article explains MySQL 8.0’s new iterator‑based executor, detailing the underlying iterator model, its advantages over the legacy executor, the specific RowIterator classes introduced, supported query features, and future enhancements for more advanced algebraic operations.
This article explains the differences between NULL and empty strings in MySQL, covering how NULL is stored, its impact on numeric and string operations, ordering, grouping, aggregation functions, and provides practical code examples and recommendations for schema design.
This article provides a detailed technical analysis of Phoenix's native index creation and maintenance mechanisms, the underlying source code for index building, the role of coprocessors, and the complete SQL compilation pipeline from parsing to execution, highlighting how hints and optimizers influence index usage.
Tencent Cloud’s database evolution progressed from early open‑source integration to self‑developed, cloud‑native solutions, producing the distributed, high‑availability TDSQL and the compute‑storage‑separated, log‑sinking CynosDB, each featuring advanced scheduling, sharding, cost‑based optimization, and asynchronous log replay to deliver scalable, low‑latency performance for diverse workloads.
The article investigates intermittent slow update performance in a Tencent Cloud internal system caused by massive lock_wait_thread contention, analyzes the underlying InnoDB lock mechanisms and thread behavior, implements a fix by disabling lock_wait_suspend_thread triggers, and demonstrates substantial latency reduction through benchmark results.
This article explains how MySQL 8.0.16's new --validate-config option can be used to test server configuration files, detect deprecated or unknown options, and obtain warnings or errors without fully starting the server.
This article examines Druid 1.1.5 connection‑pool settings—maxWait, connectionProperties, keepAlive, maxActive—illustrates real‑world cases of misconfiguration, provides recommended values, and shares a step‑by‑step investigation of a DB slow‑query incident to help engineers prevent performance and stability issues.
The article investigates why a DELETE without a WHERE clause on a 500k‑row MySQL table takes over ten hours to replay on a slave, analyzes row‑mode binlog replay mechanisms, compares different slave_rows_search_algorithms, presents test results, and offers practical recommendations for improving replication performance.
The 2019 QInfrarch technical carnival in Suzhou gathered nearly 160 engineers from Qunar and partner companies to share in‑depth sessions on private cloud databases, real‑time hotel computation, AI‑driven ticket customer service, and OceanBase architecture, concluding with networking, tea breaks, and a lucky‑draw for attendees.
This article demonstrates how to achieve ranking and pagination in MySQL using pre‑8.0 techniques such as session variables and GROUP_CONCAT, then shows the simpler native window function syntax introduced in MySQL 8.0, with complete examples, sample data, and queries for finding low‑scoring students.
Over two months, I interviewed with multiple companies for Java backend roles, sharing detailed experiences from technical rounds—covering JVM, concurrency, distributed locks, databases, and system design—to highlight key questions, effective answers, and practical advice for succeeding in similar backend development interviews.
This article provides an in‑depth technical overview of Alibaba's X‑Engine storage engine, explaining its LSM‑based architecture, compaction optimizations, transaction pipeline, caching strategies, and how these innovations enable low‑cost, high‑throughput OLTP for large‑scale e‑commerce workloads.
This article explains MongoDB 4.0's multi-document transaction support, covering replica set limitations, transaction semantics, required settings, read/write concerns, important configuration parameters, client driver versions, and provides practical shell and Python code examples.
This article explains core data‑warehouse concepts—including DB, DW, ODS, OLTP, OLAP, BI, and the differing meanings of DM—as well as their relationships, integration examples, and why OLAP cannot replace data mining, providing a concise reference for beginners in data analytics.
The article explains how MongoDB Change Streams, introduced in version 3.6 and expanded in 4.0, enable near‑real‑time subscription to collection, database, and cluster changes, discusses implementation details, options, code examples in the mongo shell and Python, and provides practical testing insights and driver compatibility notes.
The article explains how using the KEYS command on large Redis datasets can block the single‑threaded server and cause outages, and demonstrates how the incremental SCAN command safely retrieves keys without impacting performance, including syntax, options, and practical examples.
