fix-slow-queries skill

Fix Slow Queries

Deliver a measured improvement with preserved behavior and a reviewable PR whose latest commit passes checks. A list of suspicious SQL or an unverified rewrite is an intermediate result. Respect a narrower request for diagnosis only.

1. Establish the target and finish line

owning repository, and local checkout. Read its AGENTS.md and scoped rules. Paperclip and the private paperclip-cloud control plane have different rules.

• Resolve the reported URL, environment, company/workspace, deployed revision,

checkout running a live server out of branch switching and benchmark setup.

• Work in a dedicated branch/worktree. Reuse suitable existing work; keep the

deferred candidates so discovery does not turn into an unbounded rewrite.

• Select a bounded batch, usually the top two or three query families. Record

proof, relevant regression coverage, and green checks on each final PR head. A concrete access or infrastructure blocker must be reported as incomplete.

• The finish line is: reproducible baseline, faster treatment, output/behavior

2. Find the actual database and rank the work

Read Cloud discovery when starting from a hosted workspace. Follow the chain from Paperclip Cloud fleet admin to the stack's Neon project, branch, endpoint, database, and runtime role. Record the corresponding application deployment and time window. Do not reuse IDs from a previous run.

Capture query text/fingerprint, calls, total execution time, mean time, rows, and available I/O, temporary-file, and lock-wait evidence. Rank both expensive individual calls and frequent work with high aggregate cost. Group variants by their actual caller; do not add unrelated query means into an endpoint latency.

Keep three claims separate:

Cumulative query statistics are not a recent-window trace. Capture reset times or two snapshots and calculate deltas. A large database-time total alone does not justify resizing Neon. Application CPU headroom also does not rule out a busy Node main thread.

3. Trace each candidate to its behavior

Use rg on distinctive SQL fragments, table names, JSON keys, and predicates. Trace the full path: route or scheduler → service → generated SQL → indexes. Record frequency, fan-out, page limits, redaction, authorization, and any second query the caller performs. Compare the deployed implementation with local code.

State a falsifiable cause and the contract the fix must preserve. Typical causes include casts on indexed columns, repeated detoasting of large JSON, broad candidate scans, unbounded result sets, duplicate reads, and unnecessary polling. Use plans and caller evidence to choose among them.

Inspect existing indexes and recent related fixes before adding another index. For advisory locks, identify the caller, key, transaction duration, and wait chain first. Preserve checkout, leases, ownership, recovery, and no-replay rules; removing a lock or polling loop is not a query optimization by itself.

4. Reproduce the baseline locally

Read Local proof before building or changing the benchmark. Use disposable real PostgreSQL and synthetic data with representative row counts, selectivity, and payload sizes. Record the PostgreSQL version and any difference from the hosted server.

Pin the pre-fix commit. Capture the complete SQL and parameters the real service generates, including projections, joins, ordering, limits, and relevant imported query helpers. Prove the baseline exhibits the suspected cost before editing. If it does not, improve the fixture or revise the hypothesis.

Save baseline results, timings, and EXPLAIN (ANALYZE, BUFFERS, FORMAT JSON). Define the performance acceptance criterion for this fixture before measuring the treatment. Avoid a brittle universal millisecond threshold.

5. Implement and prove both kinds of green

Make the smallest change supported by the measurements. Author the fix on our branch from source and evidence. Related community reports can supply leads; respect any instruction to keep the implementation independent of their code.

Run baseline and treatment against equivalent fixtures under the same settings:

and examine plan/buffer changes. Alternate order or repeat in reverse order when caching could explain the gain. Report neutral or slower paths honestly.

• Performance: use warmups and repeated samples, report medians and spread,

behavior. Preserve ordering, duplicates, nulls, tenant scope, and redaction. A faster wrong result fails even when row counts match.

• Correctness: compare every returned SQL column and the externally visible

When intentionally bounding history, compare query speed at the same result limit separately from the contract change. Test default/max limits and older record access. Do not call truncated output equivalent to the former full list.

Reject or revise the change if either proof fails. Keep the reproducible harness with the source where repository conventions allow it; keep bulky evidence out of git. Exhaust viable query/caller changes and existing indexes before proposing an exceptional migration. Document the serious reason and why migration-free alternatives are insufficient. Do not add startup scripts, boot-time DDL, or recurring backfills to bypass the migration constraint.

If a migration remains necessary, follow the database migration rules and the production-size timing procedure in Local proof. Measure the complete migration, including index builds, backfills, and lock waits. First optimize a migration exceeding the roughly one-to-two-minute budget; if it cannot be brought within an acceptable duration, flag it for human review with the measured timings and alternatives before presenting it as deployable.

6. Verify the blast radius

Choose checks from the caller graph and affected contracts, not only the edited function. Relevant cases from this workflow include:

Use real database tests for SQL semantics. Exercise assembled services/routes and actual UI components when those are affected. Update query mocks when the builder shape changes; a broken mock is not evidence that runtime SQL is wrong.

Run focused checks first, then the owning repository's required pre-PR checks. For this repo, consult AGENTS.md for typecheck, full tests, build, and conditional map/token/migration gates. Capture command, commit, exit status, and log location. Do not call an interrupted suite a pass. Preserve its partial evidence and state what completed locally versus on the final commit in CI.

7. Create the PR and carry it through checks

Use prepare-paperclip-pr for public Paperclip changes, check-pr for feedback, and prcheckloop for checks. Follow the owning repository's workflow instead when the fix belongs in paperclip-cloud.

revision, fixture, before/after timings, equality evidence, regression results, and remaining risks. Label synthetic local timings as local SQL measurements. For an exceptional migration, include its justification, production-size fixture, complete duration, blocking time, optimization attempts, and any human decision still needed. Query speedup does not establish acceptable migration cost.

• Use the full PR template. Include cause, contract, benchmark command, baseline

dependencies. Attach every created PR to the current chat/task where supported.

• Split independent fixes into independently reviewable PRs; disclose actual

rerun affected local proof, and wait for fresh review and all expected checks on that SHA. Follow this repo's Greptile 5/5/no-unresolved-findings requirement.

• After each push, refresh the head SHA. Address actionable reviews and failures,

demonstrated transient failure once. Cancel obsolete runs only after verifying they belong to this work and an older head; never terminate unrelated jobs.

• Distinguish code failures from runner shutdowns or external outages. Rerun a

or report the exact blocker, check URL, attempts, and next action. An empty check list, an old review score, or a draft-only subset of checks is not green.

• Do not finish with "CI pending." Continue the loop within its repair bounds,

Thanking contributors and closing their PRs requires explicit authorization. When authorized, explain which report our verified PR covers, acknowledge any uncovered scope, and leave unrelated PRs open. This skill does not itself grant permission to comment, close, merge, deploy, resize, or mutate a hosted database.

Constraints

• your solution should not require a migration script to be run unless there is a serious reason - in almost all cases a migration script is a non starter
• similarly you should not add some new boot script - e.g. dont' work around migration scripts by running the migration on every boot
• if you add migrations, you should also have a sense on the time it will take on a large paperclip instance with thousands of tasks. the best option is to test on a clone of a production-size database and time it. if you don't have that you should make one. migrations that take an unacceptably large time to run (e.g. more than 1 or 2 minutes) must be flagged - first try to optimize the migration and then flag for a human if that's impossible

8. Hand off the evidence

Report each PR URL and final head, measured gains and neutral paths, correctness comparison, completed local checks, latest-head CI/review status, and limitations. If working from a Paperclip issue, attach evidence/work products using the repository's artifact workflow. Keep private identifiers and tenant data out of public PRs. State whether anything was deployed.

If rollout is authorized, verify the deployed revision and compare a fresh, comparable query-statistics window and request timing. Until then, production latency improvement remains unverified even when local SQL is much faster.