A guide for copying data from PostgreSQL, MySQL, Oracle, or Microsoft SQL Server into CockroachDB with the molt fetch command. It covers direct transfers and transfers through cloud or local storage.

Use it to configure a database migration, choose storage, control how target tables are handled, authenticate with cloud storage, and connect the migration to verification.

It provides a documented way to move large amounts of data and handle failed or resumable transfers.

molt-fetch — Skill for Claude Code and Codex by cockroachlabs

Install

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.

Any agent

npx skills add cockroachlabs/cockroachdb-skills --skill molt-fetch

Clone the repo

git clone --depth 1 https://github.com/cockroachlabs/cockroachdb-skills

Made for: Claude Code, Codex.

Wrote 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.

README.md

[![agentmods](https://agentmods.dev/badge/skills/cockroachlabs/cockroachdb-skills/molt-fetch/github.svg)](https://agentmods.dev/skills/cockroachlabs/cockroachdb-skills/molt-fetch)

Your own site

<a href="https://agentmods.dev/skills/cockroachlabs/cockroachdb-skills/molt-fetch"><img src="https://agentmods.dev/badge/skills/cockroachlabs/cockroachdb-skills/molt-fetch/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.

Your own site · 80×15

<a href="https://agentmods.dev/skills/cockroachlabs/cockroachdb-skills/molt-fetch"><img src="https://agentmods.dev/badge/skills/cockroachlabs/cockroachdb-skills/molt-fetch.svg" alt="Reviewed on agentmods" width="80" height="20"></a>

Per session 53 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.

When invoked 1,287 The whole file, excluding the scripts and references it only reads on demand.

Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.

Origin original No closer match found in the catalogue.

Token cost

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	$0.00053	$0.01287
Opus 5.5	$0.00021	$0.00515
Sonnet 5.5	$0.00011	$0.00257
Haiku 4.5	$0.00005	$0.00129

Measured 2mo ago against content hash d5e3630a1eaa, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

molt-fetch 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 2mo 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.

Origin

Copies of this mod

2 near-identical copies found in the catalogue:

molt-fetch — 100% identical, 0 lines differ
molt-fetch — 100% identical, 0 lines differ

skills/cockroachdb-onboarding-and-migrations/molt-fetch/SKILL.md · 132 lines

How it starts

The opening of the file, as written. The whole thing — 132 lines — stays where its author put it; the contents beside it link to each section on GitHub.

molt fetch

Bulk data migration from source databases (PostgreSQL, MySQL, Oracle, MSSQL) to CockroachDB.

Basic Structure

molt fetch \
  --source "<source-conn>" \
  --target "<crdb-conn>" \
  --bucket-path "s3://bucket/prefix"   # or --direct-copy or --local-path
  [options]

Storage Backends (pick one)

Option	When to use
`--bucket-path "s3://..."`	AWS S3 (also `gs://` for GCS, `azure://` for Azure)
`--direct-copy`	No intermediate storage; fastest for accessible networks
`--local-path "/tmp/molt"` + `--local-path-listen-addr "0.0.0.0:9005"`	CRDB must reach the listen addr

Cloud auth: pass --use-implicit-auth for IAM/ADC/managed identity, or set AWS_ACCESS_KEY_ID/GOOGLE_APPLICATION_CREDENTIALS env vars.

Table Handling (`--table-handling`)

Value	Behavior
`none` (default)	Append to existing tables
`drop-on-target-and-recreate`	Drop + recreate from source schema; enables auto schema creation. Destroys existing target tables and their data, so use only on fresh or empty targets
`truncate-if-exists`	Truncate before loading; errors if table missing

Import Mode

IMPORT INTO (default): Table goes OFFLINE during load. Highest throughput.

COPY FROM (--use-copy): Table stays ONLINE. Use with --direct-copy. Cannot use compression.

# Zero-downtime load
molt fetch --source "..." --target "..." --direct-copy --use-copy

Key Flags

# Filtering
--table-filter "customers|orders"      # POSIX regex for tables to include
--table-exclusion-filter "temp_.*"     # exclude pattern
--schema-filter "public"               # PostgreSQL only

# Performance
--table-concurrency 4                  # parallel tables (default: 4)
--export-concurrency 4                 # export threads (default: 4)
--row-batch-size 100000                # rows per SELECT (default: 100k)

# Schema
--type-map-file "types.json"           # custom type mappings
--transformations-file "transforms.json"  # column exclusions, table aliases

# Logging
--log-file "migration.log"             # or "stdout"
--logging debug                        # info (default), debug, trace
--metrics-listen-addr "0.0.0.0:3030"  # Prometheus scrape endpoint

Read the full file on GitHub · 132 lines

Files

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.

references/flags.md 4.6 KB

Changes

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.

2mo ago First seen · 132 lines · 53 tokens per session scan A d5e3630a1eaa

Subscribe to this mod's changes

molt-fetch is a skill published in the GitHub repository cockroachlabs/cockroachdb-skills (23 stars, last pushed 3mo ago), licensed Apache-2.0. It adds 53 tokens to every session and 1,287 once invoked, about $0.0002 per session on Opus 5.5. 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.

Databases PostgreSQL

molt-fetch next to 6 skills from other repositories
Mod	Type	Stars	Last push	Licence	Scan	Tokens	Works with
molt-fetchcockroachlabs/cockroachdb-skills	Skill	23	3mo ago	Apache-2.0	A	53	Claude Code, Codex
alloydb-basicsgoogle/skills	Skill	22k	yesterday	Apache-2.0	A	72	Claude Code, Codex
postgresql-table-designwshobson/agents	Skill	42k	yesterday	MIT	A	37	Claude Code
db-repairgarrytan/gbrain	Skill	32k	yesterday	MIT	A	96	Claude Code
volcengine-rds-postgresqlbytedance/agentkit-samples	Skill	484	today	Apache-2.0	A	63	Claude Code, Codex
dsqlawslabs/agent-plugins	Skill	937	yesterday	Apache-2.0	A	246	Claude Code
analyzing-insights-across-teamsPostHog/posthog-foss	Skill	728	yesterday	MIT	A	115	Claude Code, Codex