Getting it into your agent
One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.
npx agentmods add skills/thibautbaissac/rails_ai_agents/postgres-patternsnpx skills add ThibautBaissac/rails_ai_agents --skill postgres-patternsgit clone --depth 1 https://github.com/ThibautBaissac/rails_ai_agentsWrote this? Show the measurements
A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.
[](https://agentmods.dev/skills/thibautbaissac/rails_ai_agents/postgres-patterns)<a href="https://agentmods.dev/skills/thibautbaissac/rails_ai_agents/postgres-patterns"><img src="https://agentmods.dev/badge/skills/thibautbaissac/rails_ai_agents/postgres-patterns.svg" alt="Measured on agentmods" height="20"></a>What it costs to keep this loaded
Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5 | $0.00021 | $0.00984 |
| Opus 5 | $0.00010 | $0.00492 |
| Sonnet 5 | $0.00004 | $0.00197 |
| Haiku 4.5 | $0.00002 | $0.00098 |
Grade A, and why
postgres-patterns scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 5d ago.
A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.
Nothing flagged
None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.
This is a copy
77% identical to postgres-patterns — 23 lines differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.
How it starts
The opening of the file, as written. The whole thing — 143 lines — stays where its author put it; the contents beside it link to each section on GitHub.
PostgreSQL Patterns
Quick reference for PostgreSQL best practices. For detailed guidance, use the database-reviewer agent.
When to Activate
- Writing SQL queries or migrations
- Designing database schemas
- Troubleshooting slow queries
- Implementing Row Level Security
- Setting up connection pooling
Quick Reference
Index Cheat Sheet
| Query Pattern | Index Type | Example |
|---|---|---|
WHERE col = value |
B-tree (default) | CREATE INDEX idx ON t (col) |
WHERE col > value |
B-tree | CREATE INDEX idx ON t (col) |
WHERE a = x AND b > y |
Composite | CREATE INDEX idx ON t (a, b) |
WHERE jsonb @> '{}' |
GIN | CREATE INDEX idx ON t USING gin (col) |
WHERE tsv @@ query |
GIN | CREATE INDEX idx ON t USING gin (col) |
| Time-series ranges | BRIN | CREATE INDEX idx ON t USING brin (col) |
Data Type Quick Reference
| Use Case | Correct Type | Avoid |
|---|---|---|
| IDs | bigint |
int, random UUID |
| Strings | text |
varchar(255) |
| Timestamps | timestamptz |
timestamp |
| Money | numeric(10,2) |
float |
| Flags | boolean |
varchar, int |
Common Patterns
Composite Index Order:
-- Equality columns first, then range columns
CREATE INDEX idx ON orders (status, created_at);
-- Works for: WHERE status = 'pending' AND created_at > '2024-01-01'
Covering Index:
CREATE INDEX idx ON users (email) INCLUDE (name, created_at);
-- Avoids table lookup for SELECT email, name, created_at
Partial Index:
CREATE INDEX idx ON users (email) WHERE deleted_at IS NULL;
-- Smaller index, only includes active users
RLS Policy (Optimized):
CREATE POLICY policy ON orders
USING ((SELECT auth.uid()) = user_id); -- Wrap in SELECT!
UPSERT:
INSERT INTO settings (user_id, key, value)
VALUES (123, 'theme', 'dark')
ON CONFLICT (user_id, key)
DO UPDATE SET value = EXCLUDED.value;
Cursor Pagination:
SELECT * FROM products WHERE id > $last_id ORDER BY id LIMIT 20;
-- O(1) vs OFFSET which is O(n)
What this file has done since we first saw it
Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.
- 5d ago First seen · 143 lines · 21 tokens per session scan A f339f595f68e
postgres-patterns is a skill published in the GitHub repository ThibautBaissac/rails_ai_agents (659 stars, last pushed 3mo ago), licensed MIT. It adds 21 tokens to every session and 984 once invoked, about $0.0001 per session on Opus 5. A static security scan graded it A with 0 findings. It is 77% identical to postgres-patterns, differing in 23 lines, and is treated as a copy.
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