Tag

index scan

1 views collected around this technical thread.

Aikesheng Open Source Community
Aikesheng Open Source Community
Feb 24, 2025 · Databases

MySQL EXPLAIN EXTRA: Interpreting SEMI JOIN Hints and Related Optimizations

This article explains how to read MySQL's EXPLAIN EXTRA column, covering SEMI JOIN hints such as FirstMatch, Start/End temporary, LooseScan, and the Range‑checked‑for‑each‑record optimization, with concrete examples and command‑line output to illustrate each case.

EXPLAINMySQLQuery Optimization
0 likes · 9 min read
MySQL EXPLAIN EXTRA: Interpreting SEMI JOIN Hints and Related Optimizations
Aikesheng Open Source Community
Aikesheng Open Source Community
Jul 8, 2024 · Databases

Optimizing MySQL GROUP BY with Index Scans: Loose vs Tight Index Scan

This article explains how MySQL GROUP BY queries can be dramatically accelerated by using appropriate index scans, compares Loose Index Scan and Tight Index Scan, shows practical test data, execution plans, and provides guidelines for when each method is most effective.

GROUP BYLoose Index ScanMySQL
0 likes · 15 min read
Optimizing MySQL GROUP BY with Index Scans: Loose vs Tight Index Scan
Architecture Digest
Architecture Digest
Jan 17, 2020 · Databases

Optimizing MySQL LIMIT OFFSET Queries by Reducing Unnecessary Row Scans

This article demonstrates how rewriting a MySQL LIMIT OFFSET query to first fetch primary keys in a sub‑query and then join the main table can cut execution time from over 16 seconds to under one second by avoiding massive random I/O and buffer‑pool pollution.

Buffer PoolLimit OffsetMySQL
0 likes · 7 min read
Optimizing MySQL LIMIT OFFSET Queries by Reducing Unnecessary Row Scans
Aikesheng Open Source Community
Aikesheng Open Source Community
Sep 11, 2019 · Databases

MySQL Replication: How Slave Row Search Algorithms Influence Data Lookup

This article explains how MySQL's slave_rows_search_algorithms setting and the presence of primary or unique indexes affect the way a replica locates rows for DELETE operations, compares index‑scan, table‑scan, and hash‑scan methods, and provides practical guidance to reduce replication lag.

HASH_SCANMySQLReplication
0 likes · 11 min read
MySQL Replication: How Slave Row Search Algorithms Influence Data Lookup
360 Tech Engineering
360 Tech Engineering
Jan 7, 2019 · Databases

SQL Query Analysis and Access Path Strategies

This article explains how relational optimizers validate, analyze, and transform SQL statements into executable code, detailing the four-step optimization process, query‑analysis factors, cost‑based access‑path selection, table scans, index lookups, and the role of data prefetching in improving performance.

Access PathCost-Based OptimizerQuery Optimization
0 likes · 12 min read
SQL Query Analysis and Access Path Strategies