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.brain/.agent/skills/database-optimization/mysql/references/fulltext-indexes.md

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+---
+title: Fulltext Search Indexes
+description: Fulltext index guide
+tags: mysql, fulltext, search, indexes, boolean-mode
+---
+
+# Fulltext Indexes
+
+Fulltext indexes are useful for keyword text search in MySQL. For advanced ranking, fuzzy matching, or complex document search, prefer a dedicated search engine.
+
+```sql
+ALTER TABLE articles ADD FULLTEXT INDEX ft_title_body (title, body);
+
+-- Natural language (default, sorted by relevance)
+SELECT *, MATCH(title, body) AGAINST('database performance') AS score
+FROM articles WHERE MATCH(title, body) AGAINST('database performance');
+
+-- Boolean mode: + required, - excluded, * suffix wildcard, "exact phrase"
+WHERE MATCH(title, body) AGAINST('+mysql -postgres +optim*' IN BOOLEAN MODE);
+```
+
+## Key Gotchas
+- **Min word length**: default 3 chars (`innodb_ft_min_token_size`). Shorter words are ignored. Changing this requires rebuilding the FULLTEXT index (drop/recreate) to take effect.
+- **Stopwords**: common words excluded. Control stopwords with `innodb_ft_enable_stopword` and customize via `innodb_ft_user_stopword_table` / `innodb_ft_server_stopword_table` (set before creating the index, then rebuild to apply changes).
+- **No partial matching**: unlike `LIKE '%term%'`, requires whole tokens (except `*` in boolean mode).
+- **MATCH() columns must correspond to an index definition**: `MATCH(title, body)` needs a FULLTEXT index that covers the same column set (e.g. `(title, body)`).
+- Boolean mode without required terms (no leading `+`) can match a very large portion of the index and be slow.
+- Fulltext adds write overhead — consider Elasticsearch/Meilisearch for complex search needs.