mirror of
https://github.com/ent/ent.git
synced 2026-05-22 09:31:45 +03:00
95d878d3c6
Summary: {F206501895}
Reviewed By: alexsn
Differential Revision: D17182079
fbshipit-source-id: 9311fc8b3f2608b9cd5ae5cd0a805b0cf73c4029
115 lines
3.0 KiB
Markdown
Executable File
115 lines
3.0 KiB
Markdown
Executable File
---
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id: migrate
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title: Database Migration
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---
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The migration support for `ent` provides the option for keeping the database schema
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aligned with the schema objects defined in `ent/migrate/schema.go` under the root of your project.
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## Auto Migration
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Run the auto-migration logic in the initialization of the application:
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```go
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if err := client.Schema.Create(ctx); err != nil {
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log.Fatalf("failed creating schema resources: %v", err)
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}
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```
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`Create` creates all database resources needed for your `ent` project. By default, `Create` works
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in an *"append-only"* mode; which means, it only creates new tables and indexes, appends columns to tables or
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extends column types. For example, changing `int` to `bigint`.
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What about dropping columns or indexes?
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## Drop Resources
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`WithDropIndex` and `WithDropColumn` are 2 options for dropping table columns and indexes.
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```go
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package main
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import (
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"context"
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"log"
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"<project>/ent"
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"<project>/ent/migrate"
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"github.com/facebookincubator/ent/dialect/sql"
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)
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func main() {
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db, err := sql.Open("mysql", "root:pass@tcp(localhost:3306)/test")
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if err != nil {
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log.Fatalf("failed connecting to mysql: %v", err)
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}
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ctx := context.Background()
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client := ent.NewClient(ent.Driver(db))
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// Run migration.
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err = client.Schema.Create(
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ctx,
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migrate.WithDropIndex(true),
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migrate.WithDropColumn(true),
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)
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if err != nil {
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log.Fatalf("failed creating schema resources: %v", err)
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}
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}
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```
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In order to run the migration in debug mode (printing all SQL queries), run:
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```go
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err := client.Debug().Schema.Create(
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ctx,
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migrate.WithDropIndex(true),
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migrate.WithDropColumn(true),
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)
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if err != nil {
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log.Fatalf("failed creating schema resources: %v", err)
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}
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```
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## Universal IDs
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By default, SQL primary-keys start from 1 for each table; which means that multiple entities of different types
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can share the same ID. Unlike AWS Neptune, where vertex IDs are UUIDs.
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This does not work well if you work with [GraphQL](https://graphql.org/learn/schema/#scalar-types), which requires
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the object ID to be unique.
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To enable the Universal-IDs support for your project, pass the `WithGlobalUniqueID` option to the migration.
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```go
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package main
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import (
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"context"
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"log"
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"<project>/ent"
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"<project>/ent/migrate"
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"github.com/facebookincubator/ent/dialect/sql"
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)
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func main() {
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db, err := sql.Open("mysql", "root:pass@tcp(localhost:3306)/test")
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if err != nil {
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log.Fatalf("failed connecting to mysql: %v", err)
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}
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ctx := context.Background()
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client := ent.NewClient(ent.Driver(db))
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// Run migration.
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if err := client.Schema.Create(ctx, migrate.WithGlobalUniqueID(true)); err != nil {
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log.Fatalf("failed creating schema resources: %v", err)
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}
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}
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```
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**How does it work?** `ent` migration allocates a 1<<32 range for the IDs of each entity (table),
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and store this information in a table named `ent_types`. For example, type `A` will have the range
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of `[1,4294967296)` for its IDs, and type `B` will have the range of `[4294967296,8589934592)`, etc.
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Note that if this option is enabled, the maximum number of possible tables is **65535**. |