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Document default database behavior (#13)

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* Document default database behavior
This commit is contained in:
Joel Feinstein
2021-01-17 14:46:50 -05:00
committed by GitHub
parent d4c2e967ee
commit 79c708b645
1 changed files with 10 additions and 1 deletions
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11
Transactions.md
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@@ -39,7 +39,7 @@ val documentsWithContent = transaction {
### Working with a multiple databases
_This functionality supported since 0.10.1 version_
When you want to work with different databases then you have to store database reference returned by `Database.connect()` and provide it to `transaction` function as first parameter. As before 0.10.1, `transaction` block without parameters will work with the latest _connected_ database.
When you want to work with different databases then you have to store database reference returned by `Database.connect()` and provide it to `transaction` function as first parameter.
```kotlin
val db1 = connect("jdbc:h2:mem:db1;DB_CLOSE_DELAY=-1;", "org.h2.Driver", "root", "")
val db2 = connect("jdbc:h2:mem:db2;DB_CLOSE_DELAY=-1;", "org.h2.Driver", "root", "")
@@ -55,6 +55,15 @@ transaction(db1) {
Entities (see [[DAO API|DAO]] page) `stick` to a transaction that was used to load that entity. That means that all changes persist to the same database and what cross-database references are prohibited and will throw exceptions.
### Setting default database
`transaction` block without parameters will use the default database.
As before 0.10.1 this will be the latest _connected_ database.
It is also possible to set the default database explicitly.
```kotlin
val db = Database.connect()
TransactionManager.defaultDatabase = db
```
### Using nested transactions
Since Exposed 0.16.1 it is possible to use nested transactions. To enable this feature you should set `useNestedTransactions` on desire `Database` instance to `true`.