@@ -2,50 +2,56 @@
22
33[](https://github.com/fabianlindfors/reshape/actions/workflows/test.yaml) [](https://github.com/fabianlindfors/reshape/releases)
44
5−Reshape is an easy-to-use, zero-downtime schema migration tool for Postgres. It automatically handles complex migrations that would normally require downtime or manual multi-step changes. During a migration, Reshape ensures both the old and new schema are available at the same time, allowing you to gradually roll out your application. It will also perform all changes without excessive locking, avoiding downtime caused by blocking other queries.
5+> Also check out [ReshapeDB](https://reshapedb.com), a new database built from the ground up to make zero-downtime schema and data migrations as simple and safe as possible. If you'd like to chat about it, please [reach out](contact@reshapedb.com)!
66
7−Reshape is designed for Postgres 12 and later.
7+Reshape is an easy-to-use, zero-downtime schema migration tool for Postgres. It automatically handles complex migrations that would normally require downtime or manual multi-step changes. During a migration, Reshape ensures both the old and new schema are available at the same time, allowing you to gradually roll out your application. It will also perform all changes without excessive locking, avoiding downtime caused by blocking other queries. For a more thorough introduction to Reshape, check out the [introductory blog post](https://fabianlindfors.se/blog/schema-migrations-in-postgres-using-reshape/).
88
9−*Note: Reshape is **experimental** and should not be used in production. It can (and probably will) break your application.*
9+Designed for Postgres 12 and later.
1010
1111- [How it works](#how-it-works)
1212- [Getting started](#getting-started)
13− - [Installation](#installation)
14− - [Creating your first migration](#creating-your-first-migration)
15− - [Preparing your application](#preparing-your-application)
16− - [Running your migration](#running-your-migration)
17− - [Using during development](#using-during-development)
13+ - [Installation](#installation)
14+ - [Creating your first migration](#creating-your-first-migration)
15+ - [Preparing your application](#preparing-your-application)
16+ - [Running your migration](#running-your-migration)
17+ - [Using during development](#using-during-development)
1818- [Writing migrations](#writing-migrations)
19− - [Basics](#basics)
20− - [Tables](#tables)
21− - [Create table](#create-table)
22− - [Rename table](#rename-table)
23− - [Remove table](#remove-table)
24− - [Columns](#columns)
25− - [Add column](#add-column)
26− - [Alter column](#alter-column)
27− - [Remove column](#remove-column)
28− - [Indices](#indices)
29− - [Add index](#add-index)
30− - [Remove index](#remove-index)
19+ - [Basics](#basics)
20+ - [Tables](#tables)
21+ - [Create table](#create-table)
22+ - [Rename table](#rename-table)
23+ - [Remove table](#remove-table)
24+ - [Add foreign key](#add-foreign-key)
25+ - [Remove foreign key](#remove-foreign-key)
26+ - [Columns](#columns)
27+ - [Add column](#add-column)
28+ - [Alter column](#alter-column)
29+ - [Remove column](#remove-column)
30+ - [Indices](#indices)
31+ - [Add index](#add-index)
32+ - [Remove index](#remove-index)
33+ - [Enums](#enums)
34+ - [Create enum](#create-enum)
35+ - [Remove enum](#remove-enum)
36+ - [Custom](#custom)
37+ - [Complex changes across tables](#complex-changes-across-tables)
3138- [Commands and options](#commands-and-options)
32− - [`reshape migrate`](#reshape-migrate)
33− - [`reshape complete`](#reshape-complete)
34− - [`reshape abort`](#reshape-abort)
35− - [`reshape generate-schema-query`](#reshape-generate-schema-query)
36− - [Connection options](#connection-options)
39+ - [`reshape migration start`](#reshape-migration-start)
40+ - [`reshape migration complete`](#reshape-migration-complete)
41+ - [`reshape migration abort`](#reshape-migration-abort)
42+ - [`reshape schema-query`](#reshape-schema-query)
43+ - [Connection options](#connection-options)
3744- [License](#license)
3845
39−
4046## How it works
4147
4248Reshape works by creating views that encapsulate the underlying tables, which your application will interact with. During a migration, Reshape will automatically create a new set of views and set up triggers to translate inserts and updates between the old and new schema. This means that every deployment is a three-phase process:
4349
44−1. **Start migration** (`reshape migrate`): Sets up views and triggers to ensure both the new and old schema are usable at the same time.
50+1. **Start migration** (`reshape migration start`): Sets up views and triggers to ensure both the new and old schema are usable at the same time.
45512. **Roll out application**: Your application can be gradually rolled out without downtime. The existing deployment will continue using the old schema whilst the new deployment uses the new schema.
46−3. **Complete migration** (`reshape complete`): Removes the old schema and any intermediate data and triggers.
52+3. **Complete migration** (`reshape migration complete`): Removes the old schema and any intermediate data and triggers.
4753
48−If the application deployment fails, you should run `reshape abort` which will roll back any changes made by `reshape migrate` without losing data.
54+If the application deployment fails, you should run `reshape migration abort` which will roll back any changes made by `reshape migration start` without losing data.
4955
5056## Getting started
5157
@@ -57,7 +63,7 @@ Binaries are available for macOS and Linux under [Releases](https://github.com/f
5763
5864#### Cargo
5965
60−Reshape can be installed using [Cargo](https://doc.rust-lang.org/cargo/):
66+Reshape can be installed using [Cargo](https://doc.rust-lang.org/cargo/) (requires Rust 1.58 or later):
6167
6268```shell
6369cargo install reshape
@@ -65,10 +71,10 @@ cargo install reshape
6571
6672#### Docker
6773
68−Reshape is available as a Docker image on [Docker Hub](https://hub.docker.com/repository/docker/fabianlindfors/reshape).
74+Reshape is available as a Docker image on [Docker Hub](https://hub.docker.com/repository/docker/fabianlindfors/reshape).
6975
7076```shell
71−docker run -v $(pwd):/usr/share/app fabianlindfors/reshape reshape migrate
77+docker run -v $(pwd):/usr/share/app fabianlindfors/reshape reshape migration start
7278```
7379
7480### Creating your first migration
@@ -97,9 +103,14 @@ This is the equivalent of running `CREATE TABLE users (id INTEGER GENERATED ALWA
97103
98104### Preparing your application
99105
100−Reshape relies on your application using a specific schema. When establishing the connection to Postgres in your application, you need to run a query to select the most recent schema. This query can be generated using: `reshape generate-schema-query`.
106+Reshape relies on your application using a specific schema. When establishing the connection to Postgres in your application, you need to run a query to select the most recent schema. The simplest way to do this is to use one of the helper libraries:
107+
108+- [Rust](https://github.com/fabianlindfors/reshape-helper)
109+- [Ruby (and Rails)](https://github.com/fabianlindfors/reshape-ruby)
110+- [Python (and Django)](https://github.com/fabianlindfors/reshape-python)
111+- [Go](https://github.com/leourbina/reshape-helper)
101112
102−To pass it along to your application, you can for example use an environment variable in your run script: `RESHAPE_SCHEMA_QUERY=$(reshape generate-schema-query)`. Then in your application:
113+If your application is not using one of the languages with an available helper library, you can instead generate the query with the command: `reshape schema-query`. To pass it along to your application, you can for example use an environment variable in your run script: `RESHAPE_SCHEMA_QUERY=$(reshape schema-query)`. Then in your application:
103114
104115```python
105116# Example for Python
@@ -112,16 +123,16 @@ db.execute(reshape_schema_query)
112123To create your new `users` table, run:
113124
114125```bash
115−reshape migrate
126+reshape migration start --complete
116127```
117128
118−As this is the first migration, Reshape will automatically complete it. For subsequent migrations, you will need to first run `reshape migrate`, roll out your application and then complete the migration using `reshape complete`.
129+We use the `--complete` flag to automatically complete the migration. During a production deployment, you should first run `reshape migration start` followed by `reshape migration complete` once your application has been fully rolled out.
119130
120131If nothing else is specified, Reshape will try to connect to a Postgres database running on `localhost` using `postgres` as both username and password. See [Connection options](#connection-options) for details on how to change the connection settings.
121132
122133### Using during development
123134
124−When adding new migrations during development, we recommend running `reshape migrate` but skipping `reshape complete`. This way, the new migrations can be iterated on by updating the migration file and running `reshape abort` followed by `reshape migrate`.
135+When adding new migrations during development, we recommend running `reshape migration start` but skipping `reshape migration complete`. This way, the new migrations can be iterated on by updating the migration file and running `reshape migration abort` followed by `reshape migration start`.
125136
126137## Writing migrations
127138
@@ -156,9 +167,9 @@ Every action has a `type`. The supported types are detailed below.
156167
157168#### Create table
158169
159−The `create_table` action will create a new table with the specified columns, indices and constraints.
170+The `create_table` action will create a new table with the specified columns, indices and constraints. You can optionally provide an `up` option to backfill values from an existing table.
160171
161−*Example: create a `customers` table with a few columns and a primary key*
172+_Example: create a `customers` table with a few columns and a primary key_
162173
163174```toml
164175[[actions]]
@@ -176,13 +187,13 @@ primary_key = ["id"]
176187 type = "TEXT"
177188
178189 # Columns default to nullable
179− nullable = false
190+ nullable = false
180191
181192 # default can be any valid SQL value, in this case a string literal
182− default = "'PLACEHOLDER'"
193+ default = "'PLACEHOLDER'"
183194```
184195
185−*Example: create `users` and `items` tables with a foreign key between them*
196+_Example: create `users` and `items` tables with a foreign key between them_
186197
187198```toml
188199[[actions]]
@@ -215,11 +226,34 @@ primary_key = ["id"]
215226 referenced_columns = ["id"]
216227```
217228
229+_Example: create `profiles` table based on existing `users` table_
230+
231+```toml
232+[[actions]]
233+type = "create_table"
234+name = "profiles"
235+primary_key = ["user_id"]
236+
237+ [[actions.columns]]
238+ name = "user_id"
239+ type = "INTEGER"
240+
241+ [[actions.columns]]
242+ name = "user_email"
243+ type = "TEXT"
244+
245+ # Backfill from `users` table and copy `users.email` to `user_email` column
246+ # This will perform an upsert based on the primary key to avoid duplicate rows
247+ [actions.up]
248+ table = "users"
249+ values = { user_id = "id", user_email = "email" }
250+```
251+
218252#### Rename table
219253
220254The `rename_table` action will change the name of an existing table.
221255
222−*Example: change name of `users` table to `customers`*
256+_Example: change name of `users` table to `customers`_
223257
224258```toml
225259[[actions]]
@@ -232,7 +266,7 @@ new_name = "customers"
232266
233267The `remove_table` action will remove an existing table.
234268
235−*Example: remove `users` table*
269+_Example: remove `users` table_
236270
237271```toml
238272[[actions]]
@@ -240,13 +274,43 @@ type = "remove_table"
240274table = "users"
241275```
242276
277+#### Add foreign key
278+
279+The `add_foreign_key` action will add a foreign key between two existing tables. The migration will fail if the existing column values aren't valid references.
280+
281+_Example: create foreign key from `items` to `users` table_
282+
283+```toml
284+[[actions]]
285+type = "add_foreign_key"
286+table = "items"
287+
288+ [actions.foreign_key]
289+ columns = ["user_id"]
290+ referenced_table = "users"
291+ referenced_columns = ["id"]
292+```
293+
294+#### Remove foreign key
295+
296+The `remove_foreign_key` action will remove an existing foreign key. The foreign key will only be removed once the migration is completed, which means that your new application must continue to adhere to the foreign key constraint.
297+
298+_Example: remove foreign key `items_user_id_fkey` from `users` table_
299+
300+```toml
301+[[actions]]
302+type = "remove_foreign_key"
303+table = "items"
304+foreign_key = "items_user_id_fkey"
305+```
306+
243307### Columns
244308
245309#### Add column
246310
247−The `add_column` action will add a new column to an existing table. You can optionally provide an `up` setting. This should be an SQL expression which will be run for all existing rows to backfill the new column.
311+The `add_column` action will add a new column to an existing table. You can optionally provide an `up` setting. This should be an SQL expression which will be run for all existing rows to backfill the new column. `up` may also reference another table to perform cross-table migrations (see ["Complex changes across tables"](#complex-changes-across-tables)).
248312
249−*Example: add a new column `reference` to table `products`*
313+_Example: add a new column `reference` to table `products`_
250314
251315```toml
252316[[actions]]
@@ -260,7 +324,7 @@ table = "products"
260324 default = "10"
261325```
262326
263−*Example: replace an existing `name` column with two new columns, `first_name` and `last_name`*
327+_Example: replace an existing `name` column with two new columns, `first_name` and `last_name`_
264328
265329```toml
266330[[actions]]
@@ -296,14 +360,48 @@ column = "name"
296360down = "first_name || ' ' || last_name"
297361```
298362
363+_Example: extract nested value from unstructured JSON `data` column to new `name` column_
364+
365+```toml
366+[[actions]]
367+type = "add_column"
368+table = "users"
369+
370+# #>> '{}' converts the JSON string value to TEXT
371+up = "data['path']['to']['value'] #>> '{}'"
372+
373+ [actions.column]
374+ name = "name"
375+ type = "TEXT"
376+```
377+
378+_Example: duplicate `email` column from `users` to `profiles` table_
379+
380+```toml
381+# `profiles` has `user_id` column which maps to `users.id`
382+[[actions]]
383+type = "add_column"
384+table = "profiles"
385+
386+ [actions.column]
387+ name = "email"
388+ type = "TEXT"
389+ nullable = false
390+
391+ # When `users` is updated in the old schema, we write the email value to `profiles`
392+ [actions.up]
393+ table = "users"
394+ value = "email"
395+ where = "user_id = id"
396+```
299397
300398#### Alter column
301399
302400The `alter_column` action enables many different changes to an existing column, for example renaming, changing type and changing existing values.
303401
304−When performing more complex changes than a rename, `up` and `down` must be provided. These should be SQL expressions which determine how to transform between the new and old version of the column. Inside those expressions, you can reference the current column value by the column name.
402+When performing more complex changes than a rename, `up` and `down` should be provided. These should be SQL expressions which determine how to transform between the new and old version of the column. Inside those expressions, you can reference the current column value by the column name.
305403
306−*Example: rename `last_name` column on `users` table to `family_name`*
404+_Example: rename `last_name` column on `users` table to `family_name`_
307405
308406```toml
309407[[actions]]
@@ -315,7 +413,7 @@ column = "last_name"
315413 name = "family_name"
316414```
317415
318−*Example: change the type of `reference` column from `INTEGER` to `TEXT`*
416+_Example: change the type of `reference` column from `INTEGER` to `TEXT`_
319417
320418```toml
321419[[actions]]
@@ -330,7 +428,7 @@ down = "CAST(reference AS INTEGER)" # Converts from text value to integer
330428 type = "TEXT" # Previous type was 'INTEGER'
331429```
332430
333−*Example: increment all values of an `index` column by one*
431+_Example: increment all values of an `index` column by one_
334432
335433```toml
336434[[actions]]
@@ -345,7 +443,22 @@ down = "index - 1" # Decrement to revert for old schema
345443 name = "index"
346444```
347445
348−*Example: change default value of `created_at` column to current time*
446+_Example: make `name` column not nullable_
447+
448+```toml
449+[[actions]]
450+type = "alter_column"
451+table = "users"
452+column = "name"
453+
454+# Use "N/A" for any rows that currently have a NULL name
455+up = "COALESCE(name, 'N/A')"
456+
457+ [actions.changes]
458+ nullable = false
459+```
460+
461+_Example: change default value of `created_at` column to current time_
349462
350463```toml
351464[[actions]]
@@ -359,9 +472,11 @@ column = "created_at"
359472
360473#### Remove column
361474
362−The `remove_column` action will remove an existing column from a table. You can optionally provide a `down` setting. This should be an SQL expression which will be used to determine values for the old schema when inserting or updating rows using the new schema. The `down` setting must be provided when the removed column is `NOT NULL` or doesn't have a default value.
475+The `remove_column` action will remove an existing column from a table. You can optionally provide a `down` setting. This should be an SQL expression which will be used to determine values for the old schema when inserting or updating rows using the new schema. `down` may also reference another table to perform cross-table migrations (see ["Complex changes across tables"](#complex-changes-across-tables)) . The `down` setting must be provided when the removed column is `NOT NULL` or doesn't have a default value.
476+
477+Any indices that cover the column will be removed.
363478
364−*Example: remove column `name` from table `users`*
479+_Example: remove column `name` from table `users`_
365480
366481```toml
367482[[actions]]
@@ -373,18 +488,34 @@ column = "name"
373488down = "'N/A'"
374489```
375490
491+_Example: remove `email` column from `users` table and use column from `profiles` table instead_
492+
493+```toml
494+[[actions]]
495+type = "remove_column"
496+table = "users"
497+column = "email"
498+
499+ # Our application will use the `profiles.email` column instead
500+ # For backwards compatibility, we will write back to the removed `email` column whenever `profiles` is changed
501+ [actions.down]
502+ table = "profiles"
503+ value = "profiles.email"
504+ where = "users.id = profiles.user_id"
505+```
506+
376507### Indices
377508
378509#### Add index
379510
380511The `add_index` action will add a new index to an existing table.
381512
382−*Example: create a `users` table with a unique index on the `name` column*
513+_Example: create a `users` table with a unique index on the `name` column_
383514
384515```toml
385516[[actions]]
386517type = "create_table"
387−table = "users"
518+name = "users"
388519primary_key = "id"
389520
390521 [[actions.columns]]
@@ -408,7 +539,7 @@ table = "users"
408539 unique = true
409540```
410541
411−*Example: add GIN index to `data` column on `products` table*
542+_Example: add GIN index to `data` column on `products` table_
412543
413544```toml
414545[[actions]]
@@ -427,7 +558,7 @@ table = "products"
427558
428559The `remove_index` action will remove an existing index. The index won't actually be removed until the migration is completed.
429560
430−*Example: remove the `name_idx` index*
561+_Example: remove the `name_idx` index_
431562
432563```toml
433564[[actions]]
@@ -435,61 +566,205 @@ type = "remove_index"
435566index = "name_idx"
436567```
437568
569+### Enums
570+
571+#### Create enum
572+
573+The `create_enum` action will create a new [enum type](https://www.postgresql.org/docs/current/datatype-enum.html) with the specified values.
574+
575+_Example: add a new `mood` enum type with three possible values_
576+
577+```toml
578+[[actions]]
579+type = "create_enum"
580+name = "mood"
581+values = ["happy", "ok", "sad"]
582+```
583+
584+#### Remove enum
585+
586+The `remove_enum` action will remove an existing [enum type](https://www.postgresql.org/docs/current/datatype-enum.html). Make sure all usages of the enum has been removed before running the migration. The enum will only be removed once the migration is completed.
587+
588+_Example: remove the `mood` enum type_
589+
590+```toml
591+[[actions]]
592+type = "remove_enum"
593+enum = "mood"
594+```
595+
596+### Custom
597+
598+The `custom` action lets you create a migration which runs custom SQL. It should be used with great care as it provides no guarantees of zero-downtime and will simply run whatever SQL is provided. Use other actions whenever possible as they are explicitly designed for zero downtime.
599+
600+There are three optional settings available which all accept SQL queries. All queries need to be idempotent, for example by using `IF NOT EXISTS` wherever available.
601+
602+- `start`: run when a migration is started using `reshape migration start`
603+- `complete`: run when a migration is completed using `reshape migration complete`
604+- `abort`: run when a migration is aborted using `reshape migration abort`
605+
606+_Example: enable PostGIS and pg_stat_statements extensions_
607+
608+```toml
609+[[actions]]
610+type = "custom"
611+
612+start = """
613+ CREATE EXTENSION IF NOT EXISTS postgis;
614+ CREATE EXTENSION IF NOT EXISTS pg_stat_statements;
615+"""
616+
617+abort = """
618+ DROP EXTENSION IF EXISTS postgis;
619+ DROP EXTENSION IF EXISTS pg_stat_statements;
620+"""
621+```
622+
623+### Complex changes across tables
624+
625+The `up` and `down` options available when creating tables, adding columns and removing columns can also perform more complex changes that span tables.
626+
627+_Example: move `email` column from `users` to `profiles` table_
628+
629+```toml
630+[[actions]]
631+type = "add_column"
632+table = "profiles"
633+
634+ [actions.column]
635+ name = "email"
636+ type = "TEXT"
637+ nullable = false
638+
639+ # When `users` is updated in the old schema, we write the email value to `profiles`
640+ [actions.up]
641+ table = "users"
642+ value = "users.email"
643+ where = "profiles.user_id = users.id"
644+
645+[[actions]]
646+type = "remove_column"
647+table = "users"
648+column = "email"
649+
650+ # When `profiles` is changed in the new schema, we write the email address back to the removed column
651+ [actions.down]
652+ table = "profiles"
653+ value = "profiles.email"
654+ where = "users.id = profiles.user_id"
655+```
656+
657+_Example: turn a 1:N relationship between `users` and `accounts` into N:M and change the format of the associated `role`_
658+
659+```toml
660+# Add `user_account_connections` as a junction table
661+[[actions]]
662+type = "create_table"
663+name = "user_account_connections"
664+primary_key = ["account_id", "user_id"]
665+
666+ [[actions.columns]]
667+ name = "account_id"
668+ type = "INTEGER"
669+
670+ [[actions.columns]]
671+ name = "user_id"
672+ type = "INTEGER"
673+
674+ # `role` is currently stored directly on the `users` table but is part of the relationship
675+ [[actions.columns]]
676+ name = "role"
677+ type = "TEXT"
678+ nullable = false
679+
680+ # Backfill the new table from `users` and uppercase the `role`
681+ [actions.up]
682+ table = "users"
683+ values = { user_id = "id", account_id = "account_id", role = "UPPER(account_role)" }
684+ where = "user_account_connections.user_id = users.id"
685+
686+[[actions]]
687+type = "remove_column"
688+table = "users"
689+column = "account_id"
690+
691+ # When `user_account_connections` is updated, we write the `account_id` back to `users`
692+ [actions.down]
693+ table = "user_account_connections"
694+ value = "user_account_connections.account_id"
695+ where = "users.id = user_account_connections.user_id"
696+
697+[[actions]]
698+type = "remove_column"
699+table = "users"
700+column = "account_role"
701+
702+ # When `user_account_connections` is updated, we write the lowercase role back to `users`
703+ [actions.down]
704+ table = "user_account_connections"
705+ value = "LOWER(user_account_connections.role)"
706+ where = "users.id = user_account_connections.user_id"
707+```
708+
438709## Commands and options
439710
440−### `reshape migrate`
711+### `reshape migration start`
441712
442−Starts a new migration, applying all migrations under `migrations/` that haven't yet been applied. After the command has completed, both the old and new schema will be usable at the same time. When you have rolled out the new version of your application which uses the new schema, you should run `reshape complete`.
713+Starts a new migration, applying all migrations under `migrations/` that haven't yet been applied. After the command has completed, both the old and new schema will be usable at the same time. When you have rolled out the new version of your application which uses the new schema, you should run `reshape migration complete`.
443714
444715#### Options
445716
446−*See also [Connection options](#connection-options)*
717+_See also [Connection options](#connection-options)_
447718
448−| Option | Default | Description |
449−| ------ | ------- | ----------- |
450−| `--complete`, `-c` | `false` | Automatically complete migration after applying it. |
451−| `--dirs` | `migrations/` | Directories to search for migration files. Multiple directories can be specified using `--dirs dir1 dir2 dir3`. |
719+| Option | Default | Description |
720+| ------------------ | ------------- | --------------------------------------------------------------------------------------------------------------- |
721+| `--complete`, `-c` | `false` | Automatically complete migration after applying it. |
722+| `--dirs` | `migrations/` | Directories to search for migration files. Multiple directories can be specified using `--dirs dir1 dir2 dir3`. |
452723
453−### `reshape complete`
724+### `reshape migration complete`
454725
455−Completes migrations previously started with `reshape complete`.
726+Completes migrations previously started with `reshape migration complete`.
456727
457728#### Options
458729
459730See [Connection options](#connection-options)
460731
461−### `reshape abort`
732+### `reshape migration abort`
462733
463−Aborts any migrations which haven't yet been completed.
734+Aborts any migrations which haven't yet been completed.
464735
465736#### Options
466737
467738See [Connection options](#connection-options)
468739
469−### `reshape generate-schema-query`
740+### `reshape schema-query`
470741
471742Generates the SQL query you need to run in your application before using the database. This command does not require a database connection. Instead it will generate the query based on the latest migration in the `migrations/` directory (or the directories specified by `--dirs`).
472743
744+If your application is written in Rust, we recommend using the [Rust helper library](https://github.com/fabianlindfors/reshape-helper/) instead.
745+
473746The query should look something like `SET search_path TO migration_1_initial_migration`.
474747
475748#### Options
476749
477−| Option | Default | Description |
478−| ------ | ------- | ----------- |
750+| Option | Default | Description |
751+| -------- | ------------- | --------------------------------------------------------------------------------------------------------------- |
479752| `--dirs` | `migrations/` | Directories to search for migration files. Multiple directories can be specified using `--dirs dir1 dir2 dir3`. |
480753
481754### Connection options
482755
483−The options below can be used with all commands that communicate with Postgres. Use either a connection URL or specify each connection option individually.
756+The options below can be used with all commands that communicate with Postgres. Use either a [connection URL](https://www.postgresql.org/docs/current/libpq-connect.html#LIBPQ-CONNSTRING) or specify each connection option individually.
757+
758+All options can also be set using environment variables instead of flags. If a `.env` file exists, then variables will be automatically loaded from there.
484759
485−| Option | Default | Description |
486−| ------ | ------- | ----------- |
487−| `--url` | | URI to connect to your Postgres database.<br>Can also be provided with the environment variable `DATABASE_URL`. |
488−| `--host` | `localhost` | Hostname to use when connecting to Postgres |
489−| `--port` | `5432` | Port which Postgres is listening on |
490−| `--database` | `postgres` | Database name |
491−| `--username` | `postgres` | Postgres username |
492−| `--password` | `postgres` | Postgres password |
760+| Option | Default | Environment variable | Description |
761+| ------------ | ----------- | -------------------- | ------------------------------------------- |
762+| `--url` | | `DB_URL` | URL to your Postgres database |
763+| `--host` | `localhost` | `DB_HOST` | Hostname to use when connecting to Postgres |
764+| `--port` | `5432` | `DB_PORT` | Port which Postgres is listening on |
765+| `--database` | `postgres` | `DB_NAME` | Database name |
766+| `--username` | `postgres` | `DB_USERNAME` | Postgres username |
767+| `--password` | `postgres` | `DB_PASSWORD` | Postgres password |
493768
494769## License
495770