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ent/doc: add documentation and exmples to offline migrate

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Summary: https://pxl.cl/Knr4

Reviewed By: alexsn

Differential Revision: D17253380

fbshipit-source-id: 517985f1b912c68e379da3412863b5d14927aedc
This commit is contained in:
Ariel Mashraki
2019-09-09 01:18:52 -07:00
committed by Facebook Github Bot
parent b2cedc6c95
commit 5fb8c081f3
1 changed files with 70 additions and 1 deletions
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doc/md/migrate.md
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@@ -112,4 +112,73 @@ func main() {
and store this information in a table named `ent_types`. For example, type `A` will have the range
of `[1,4294967296)` for its IDs, and type `B` will have the range of `[4294967296,8589934592)`, etc.
Note that if this option is enabled, the maximum number of possible tables is **65535**.
Note that if this option is enabled, the maximum number of possible tables is **65535**.
## Offline Mode
Offline mode allows you to write the schema changes to an `io.Writer` before executing them on the database.
It's useful for verifying the SQL commands before they're executed on the database, or to get an SQL script
to run manually.
**Print changes**
```go
package main
import (
"context"
"log"
"os"
"<project>/ent"
"<project>/ent/migrate"
"github.com/facebookincubator/ent/dialect/sql"
)
func main() {
db, err := sql.Open("mysql", "root:pass@tcp(localhost:3306)/test")
if err != nil {
log.Fatalf("failed connecting to mysql: %v", err)
}
ctx := context.Background()
client := ent.NewClient(ent.Driver(db))
// Dump migration changes to stdout.
if err := client.Schema.WriteTo(ctx, os.Stdout); err != nil {
log.Fatalf("failed printing schema changes: %v", err)
}
}
```
**Write changes to file**
```go
package main
import (
"context"
"log"
"os"
"<project>/ent"
"<project>/ent/migrate"
"github.com/facebookincubator/ent/dialect/sql"
)
func main() {
db, err := sql.Open("mysql", "root:pass@tcp(localhost:3306)/test")
if err != nil {
log.Fatalf("failed connecting to mysql: %v", err)
}
ctx := context.Background()
client := ent.NewClient(ent.Driver(db))
// Dump migration changes to an SQL script.
f, err := os.Create("migrate.sql")
if err != nil {
log.Fatalf("create migrate file: %v", err)
}
defer f.Close()
if err := client.Schema.WriteTo(ctx, f); err != nil {
log.Fatalf("failed printing schema changes: %v", err)
}
}
```