performance-optimization

SKILL.md

| includes | Most cases (Rails chooses best strategy) | | preload | Forcing separate queries, large datasets | | eagerload | Filtering on association, need single query | | joins | Only need to filter, don't need association data |

| Foreign keys | accountid, userid | | Columns in WHERE | WHERE status = 'active' | | Columns in ORDER BY | ORDER BY createdat DESC | | Columns in JOIN | JOIN ON events.venueid | | Unique constraints | email, uuid |

| N+1 on belongsto | includes(:association) | | N+1 on hasmany | includes(:association) | | Slow COUNT | Add countercache | | Loading all columns | Use select or pluck | | Large dataset iteration | Use findeach | | Missing index on FK | Add index on id columns | | Slow WHERE clause | Add index on filtered column |

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