How do you optimize a slow SQLite query?

Optimization generally follows a consistent sequence: understand what the query planner is actually doing, then address the specific gap that's causing it to do more work than necessary.

1. Run EXPLAIN QUERY PLAN to see whether the query is using an index (SEARCH) or scanning the whole table (SCAN).
2. Add an index on columns used in WHERE, JOIN conditions, or ORDER BY, if a full scan shows up where a targeted lookup would be expected.
3. Consider a covering index that includes every column the query needs, letting SQLite skip the second B-tree traversal to fetch the full row.
4. Run ANALYZE if the planner seems to be choosing a poor index despite one existing — stale or missing statistics can lead it astray.
5. Avoid functions on indexed columns in WHERE clauses (like WHERE lower(name) = 'ada'), since that typically prevents the index on name from being used at all, unless an expression index is created specifically for that expression.

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