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In action
Full scans, non-sargable filters and accidental cartesian joins — named in plain language and ranked by impact.
Try SQL Optimizer3–8× faster · 2 full-table scans eliminated
Rewrote comma join to explicit JOIN, removed function wrap on email column
CREATE INDEX statements built from your real filters and join keys — not generic advice you have read ten times.
Plain-language diagnosis of every performance issue, ranked by impact
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Same results, fewer bottlenecks — sargable predicates, tightened joins and projection instead of SELECT star.
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Function wrapping prevents the index on email from being used — rewrite as email = lower($1).
SELECT
o.id, o.amount, o.status,
c.email, c.name
FROM orders o
JOIN customers c ON o.customer_id = c.id
WHERE c.email = lower($1)
AND o.status <> 'cancelled'
ORDER BY o.created_at DESCCREATE INDEX ON customers (lower(email));
CREATE INDEX ON orders (customer_id, status, created_at DESC);Validate the rewrite returns identical rows before replacing anything in production.