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 skills add sandeepmvl/rails-skills --skill 21-db-migration-postgres-mysqlgit clone --depth 1 https://github.com/sandeepmvl/rails-skillsWrote 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/sandeepmvl/rails-skills/21-db-migration-postgres-mysql)<a href="https://agentmods.dev/skills/sandeepmvl/rails-skills/21-db-migration-postgres-mysql"><img src="https://agentmods.dev/badge/skills/sandeepmvl/rails-skills/21-db-migration-postgres-mysql/github.svg" alt="Measured on agentmods" height="20"></a>Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.
<a href="https://agentmods.dev/skills/sandeepmvl/rails-skills/21-db-migration-postgres-mysql"><img src="https://agentmods.dev/badge/skills/sandeepmvl/rails-skills/21-db-migration-postgres-mysql.svg" alt="Reviewed on agentmods" width="80" 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 5.1 | $0.00129 | $0.01929 |
| Opus 5 | $0.00064 | $0.00964 |
| Sonnet 5 | $0.00026 | $0.00386 |
| Haiku 4.5 | $0.00013 | $0.00193 |
Grade A, and why
db-migration-postgres-mysql 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 11d 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.
How it starts
The opening of the file, as written. The whole thing — 229 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Postgres → MySQL Migration
Going from Postgres to MySQL is a downgrade in feature set. Plan for what you'll lose (JSONB-style operators, array columns, partial indexes, rich
CHECKconstraints, generated columns until 8.0, true sequences) and design around it.
The opinion
Don't do this unless forced. Postgres is the Rails-community default for good reason. If forced (vendor mandate, hosting choice, cost), use
pgloaderfor the bulk migration, dual-write during cutover, and audit every column-type-specific feature in the schema before flipping.
Counter-position: MySQL 8.0+ has closed many gaps (JSON functions, generated columns, CHECK constraints enforced). For simple Rails schemas, the migration is straightforward. The complexity is per-feature.
Pre-migration audit
# Catalog every Postgres-specific feature in your schema
grep -E "jsonb|ARRAY|generated as identity|::regclass|@>|<@|tsvector" db/structure.sql
| Feature | Postgres | MySQL 8 equivalent | Migration impact |
|---|---|---|---|
JSONB |
Yes — indexed, queryable | JSON (no GIN indexes) |
Lose @> containment operator; queries via JSON_CONTAINS |
ARRAY columns (integer[]) |
Yes | None | Move to a join table or serialized text |
Partial indexes (WHERE x IS NULL) |
Yes | No (use generated columns + index) | Per-index migration |
CHECK constraints |
Yes, enforced | 8.0.16+ enforced | Verify MySQL version |
tsvector / full-text |
Yes | MySQL has its own; different API | Rewrite full-text queries |
UUID type |
Yes (uuid) |
CHAR(36) or BINARY(16) |
App-side normalization |
| Sequences | Yes | AUTO_INCREMENT only | Single-PK sequences fine; named/multi-table sequences need redesign |
| Case sensitivity (LIKE) | Case-sensitive | Case-insensitive by default | Migrate to LIKE BINARY for strict; or accept the change |
Core patterns
Pattern 1: Schema conversion via pgloader
# Install pgloader
brew install pgloader
# Migration script
cat > migrate.load <<EOF
LOAD DATABASE
FROM postgresql://user:pass@source-host/myapp_production
INTO mysql://user:pass@target-host/myapp_production
WITH include drop, create tables, create indexes, reset sequences,
workers = 8, concurrency = 1
SET MySQL PARAMETERS
net_buffer_length to '16M',
max_allowed_packet to '128M'
CAST type jsonb to json,
type uuid to varchar(36)
;
EOF
pgloader migrate.load
What ships with it
1 file beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.
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.
- 11d ago First seen · 229 lines · 129 tokens per session scan A 6048c6c8f9e8
db-migration-postgres-mysql is a skill published in the GitHub repository sandeepmvl/rails-skills (21 stars, last pushed 3mo ago), licensed MIT. It adds 129 tokens to every session and 1,929 once invoked, about $0.0006 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.
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