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63 lines
2.4 KiB
Markdown
63 lines
2.4 KiB
Markdown
# Axum App with multi-database Database
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This example project involves three crates, each owning a different schema in one database,
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with their own set of migrations.
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* The main crate, a simple binary simulating the action of a REST API.
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* Owns the `public` schema (tables are referenced unqualified).
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* Migrations are moved to `src/migrations` using config key `migrate.migrations-dir`
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to visually separate them from the subcrate folders.
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* `accounts`: a subcrate simulating a reusable account-management crate.
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* Owns schema `accounts`.
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* `payments`: a subcrate simulating a wrapper for a payments API.
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* Owns schema `payments`.
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## Note: Schema-Qualified Names
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This example uses schema-qualified names everywhere for clarity.
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It can be tempting to change the `search_path` of the connection (MySQL, Postgres) to eliminate the need for schema
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prefixes, but this can cause some really confusing issues when names conflict.
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This example will generate a `_sqlx_migrations` table in three different schemas; if `search_path` is set
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to `public,accounts,payments` and the migrator for the main application attempts to reference the table unqualified,
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it would throw an error.
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# Setup
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This example requires running three different sets of migrations.
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Ensure `sqlx-cli` is installed with Postgres and `sqlx.toml` support:
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```
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cargo install sqlx-cli --features postgres,sqlx-toml
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```
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Start a Postgres server (shown here using Docker, `run` command also works with `podman`):
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```
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docker run -d -e POSTGRES_PASSWORD=password -p 5432:5432 --name postgres postgres:latest
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```
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Create `.env` with the various database URLs or set them in your shell environment;
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```
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DATABASE_URL=postgres://postgres:password@localhost/example-multi-database
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ACCOUNTS_DATABASE_URL=postgres://postgres:password@localhost/example-multi-database-accounts
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PAYMENTS_DATABASE_URL=postgres://postgres:password@localhost/example-multi-database-payments
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```
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Run the following commands:
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```
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(cd accounts && sqlx db setup)
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(cd payments && sqlx db setup)
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sqlx db setup
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```
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It is an open question how to make this more convenient; `sqlx-cli` could gain a `--recursive` flag that checks
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subdirectories for `sqlx.toml` files, but that would only work for crates within the same workspace. If the `accounts`
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and `payments` crates were instead crates.io dependencies, we would need Cargo's help to resolve that information.
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An issue has been opened for discussion: <https://github.com/launchbadge/sqlx/issues/3761>
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