/psql-query

name: psql-query
description: Run ad-hoc PostgreSQL analytics queries against dev/test database

PostgreSQL Analytics

Run analytics queries against the local database using psql or `mix run`.

Rules

• NEVER run against production
• Use READ-ONLY queries (SELECT only)
• For complex analysis, use `Repo.query/2` in a Mix task
• Format results as ASCII tables or pipe to `column -t`

Tidewave Integration

If Tidewave MCP is available, prefer it over psql/mix run:

• `mcp__tidewave__execute_sql_query` for direct SQL queries
• `mcp__tidewave__project_eval` for Ecto-based queries via `Repo.query!/2` or `Repo.all/1`

Fall back to psql/mix run only if Tidewave is not detected.

Workflow

1. Check if Tidewave MCP is available — if yes, use `mcp__tidewave__execute_sql_query` 2. Otherwise, detect database URL from `config/dev.exs` or `DATABASE_URL` 3. Run query via: `psql $DATABASE_URL -c "YOUR QUERY" --expanded` 4. For Ecto: `mix run -e 'MyApp.Repo.query!("SELECT ...") |> IO.inspect()'` 5. Summarize results

Example prompts

• "How many users signed up this week?"
• "Show me the slowest queries from pg_stat_statements"
• "What's the table size distribution?"
• "Show index usage stats"