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pg-explain

Use when a Postgres query is slow or EXPLAIN shows a sequential scan, an endpoint is slow because of SQL, or you are adding a query against a large table.

Skill by Srimukh99

IndexedMIT
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Works with Claude Code, Claude apps, Codex, Cursor, Gemini CLI, GitHub Copilot, VS Code, OpenCode, Goose, Windsurf. Read the repository before you give any tool access to your data.

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About

Use when a Postgres query is slow or EXPLAIN shows a sequential scan, an endpoint is slow because of SQL, or you are adding a query against a large table. Reads the plan and fixes the cause with measured before and after timings.

Use cases: backend, data

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What this skill can do and what it asks for, from its SKILL.md. Checked Oct 25, 2026.

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Network hosts it talks to 1

  • codeload.github.com · found in install command

Files it touches

  • ~/.claude/skills/pg-explain

What's inside

Skill name
pg-explain
Description
Use when a Postgres query is slow or EXPLAIN shows a sequential scan, an endpoint is slow because of SQL, or you are adding a query against a large table. Reads the plan and fixes the cause with measured before and after timings.
License
MIT
Instructions
29 lines in SKILL.md · view on GitHub

Files (1)

  • SKILL.md

SKILL.md (first lines)

# pg-explain

## 1. Find the query

Use `pg_stat_statements` ordered by `total_exec_time` to find the top offenders, or take the query from the slow log or trace.

## 2. Get the real plan

`EXPLAIN (ANALYZE, BUFFERS) <query>;` on production-like data. `ANALYZE` executes the query, so wrap writes in `BEGIN; ... ROLLBACK;`.

## 3. Read it

| You see | Likely cause | Try |
| --- | --- | --- |
| Estimated rows far from actual (10x+) | Stale or missing statistics | `ANALYZE <table>`; extended statistics for correlated columns |
| Seq Scan on a big table with a selective filter | Missing or unusable index | Index on the filter columns; avoid functions on the column or add an expression index |
| Nested Loop with a large outer side | Bad estimate or missing join index | Fix stats; index the join key |
| Sort or Hash with `external merge` / disk | Not enough memory or no index for order | Index matching `ORDER BY`; raise `work_mem` for that query only |
| High `shared read` buffers | Data not cached, too much scanned | Narrow the query; covering index (`INCLUDE`) |

## 4. Choose the index type

B-tree for equality and ranges; GIN for JSONB, arrays and full-text; GiST for geometry and ranges; BRIN for huge append-only tables ordered by time. Partial indexes when queries always filter the same subset.

## 5. Prove it

Change one thing, re-run `EXPLAIN ANALYZE`, and report before and after execution time (`ship`). New indexes on live tables go through `pg-migrate`. Check that you're not duplicating an existing index; each one slows writes.

From Srimukh99/rubric, MIT.

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Last commit (this folder)
Oct 4, 2026 (25 days ago)

From GitHub (fetched Oct 24, 2026).

Details

License
MIT
Repository
github.com/Srimukh99/rubric
First seen
Oct 24, 2026
Last checked
Oct 24, 2026
Source
GitHubgithub-graphql

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pg-explain skill. Agent Mart. https://agentmart.dev/skills/srimukh99-pg-explain (last updated 2026-10-24)