pgsync

Sync data from one Postgres database to another (like pg_dump/pg_restore). Designed for:

• speed - tables are transferred in parallel
• security - built-in methods to prevent sensitive data from ever leaving the server
• flexibility - gracefully handles schema differences, like missing columns and extra columns
• convenience - sync partial tables, groups of tables, and related records

🍊 Battle-tested at Instacart

Installation

pgsync is a command line tool. To install, run:

gem install pgsync

This will give you the pgsync command. If installation fails, you may need to install dependencies.

Setup

In your project directory, run:

pgsync --init

This creates .pgsync.yml for you to customize. We recommend checking this into your version control (assuming it doesn’t contain sensitive information). pgsync commands can be run from this directory or any subdirectory.

How to Use

Sync all tables

pgsync

Note: pgsync assumes your schema is setup in your to database. See the schema section if that’s not the case.

Sync specific tables

pgsync table1,table2

Sync specific rows (existing rows are overwritten)

pgsync products "where store_id = 1"

You can also preserve existing rows

pgsync products "where store_id = 1" --preserve

Or truncate them

pgsync products "where store_id = 1" --truncate

Exclude Tables

pgsync --exclude users

To always exclude, add to .pgsync.yml.

exclude:
  - table1
  - table2

For Rails, you probably want to exclude schema migrations and Active Record metadata.

exclude:
  - schema_migrations
  - ar_internal_metadata

Groups

Define groups in .pgsync.yml:

groups:
  group1:
    - table1
    - table2

And run:

pgsync group1

You can also use groups to sync a specific record and associated records in other tables.

To get product 123 with its reviews, last 10 coupons, and store, use:

groups:
  product:
    products: "where id = {1}"
    reviews: "where product_id = {1}"
    coupons: "where product_id = {1} order by created_at desc limit 10"
    stores: "where id in (select store_id from products where id = {1})"

And run:

pgsync product:123

Schema

Note: pgsync is designed to sync data. You should use a schema migration tool to manage schema changes. The methods in this section are provided for convenience but not recommended.

Sync schema before the data

pgsync --schema-first

Note: This wipes out existing data

Specify tables

pgsync table1,table2 --schema-first

Or just the schema

pgsync --schema-only

pgsync does not try to sync Postgres extensions.

Sensitive Data

Prevent sensitive data like email addresses from leaving the remote server.

Define rules in .pgsync.yml:

data_rules:
  email: unique_email
  last_name: random_letter
  birthday: random_date
  users.auth_token:
    value: secret
  visits_count:
    statement: "(RANDOM() * 10)::int"
  encrypted_*: null

last_name matches all columns named last_name and users.last_name matches only the users table. Wildcards are supported, and the first matching rule is applied.

Options for replacement are:

• unique_email
• unique_phone
• unique_secret
• random_letter
• random_int
• random_date
• random_time
• random_ip
• value
• statement
• null
• untouched

Rules starting with unique_ require the table to have a primary key. unique_phone requires a numeric primary key.

Foreign Keys

Foreign keys can make it difficult to sync data. Three options are:

1. Manually specify the order of tables
2. Use deferrable constraints
3. Disable foreign key triggers, which can silently break referential integrity

When manually specifying the order, use --jobs 1 so tables are synced one-at-a-time.

pgsync table1,table2,table3 --jobs 1

If your tables have deferrable constraints, use:

pgsync --defer-constraints

To disable foreign key triggers and potentially break referential integrity, use:

pgsync --disable-integrity

Triggers

Disable user triggers with:

pgsync --disable-user-triggers

Append-Only Tables

For extremely large, append-only tables, sync in batches.

pgsync large_table --in-batches

The script will resume where it left off when run again, making it great for backfills.

Connection Security

Always make sure your connection is secure when connecting to a database over a network you don’t fully trust. Your best option is to connect over SSH or a VPN. Another option is to use sslmode=verify-full. If you don’t do this, your database credentials can be compromised.

Safety

To keep you from accidentally overwriting production, the destination is limited to localhost or 127.0.0.1 by default.

To use another host, add to_safe: true to your .pgsync.yml.

Multiple Databases

To use with multiple databases, run:

pgsync --init db2

This creates .pgsync-db2.yml for you to edit. Specify a database in commands with:

pgsync --db db2

Other Commands

Help

pgsync --help

Version

pgsync --version

List tables

pgsync --list

Scripts

Use groups when possible to take advantage of parallelism.

For Ruby scripts, you may need to do:

Bundler.with_unbundled_env do
  system "pgsync ..."
end

Dependencies

If installation fails, your system may be missing Ruby or libpq.

On Mac, run:

brew install postgresql

On Ubuntu, run:

sudo apt-get install ruby-dev libpq-dev build-essential

Upgrading

Run:

gem install pgsync

To use master, run:

gem install specific_install
gem specific_install https://github.com/ankane/pgsync.git

Related Projects

Also check out:

• Dexter - The automatic indexer for Postgres
• PgHero - A performance dashboard for Postgres
• pgslice - Postgres partitioning as easy as pie

Thanks

Inspired by heroku-pg-transfer.

Contributing

Everyone is encouraged to help improve this project. Here are a few ways you can help:

• Report bugs
• Fix bugs and submit pull requests
• Write, clarify, or fix documentation
• Suggest or add new features

To get started with development:

git clone https://github.com/ankane/pgsync.git
cd pgsync
bundle install

createdb pgsync_test1
createdb pgsync_test2
createdb pgsync_test3

bundle exec rake test