IsolationLevel (Carbonado 1.2.3 API)

java.lang.Object
+
- java.lang.Enum<IsolationLevel>
- +
  - com.amazon.carbonado.IsolationLevel
  +
+

+
+
All Implemented Interfaces:
+
java.io.Serializable, java.lang.Comparable<IsolationLevel>
+
+
+
+
```
public enum IsolationLevel
+extends java.lang.Enum<IsolationLevel>
```
+
Describes a transaction isolation level. Transaction levels, in order from + lowest to highest are: + +
- READ_UNCOMMITTED +
- READ_COMMITTED +
- REPEATABLE_READ +
- SNAPSHOT +
- SERIALIZABLE +
+ + A transaction's isolation level is usually READ_COMMITTED or + REPEATABLE_READ by default. Forcing a lower level, like + READ_COMMITTED, is useful when performing a long cursor + iteration. It releases locks during iteration rather than holding on to them + until the transaction exits. + +
SNAPSHOT isolation is special in that it uses multiversion + concurrency control (MVCC). A commit may fail with an OptimisticLockException. Few repositories are expected to support this + level, however.
+
Author:
+
Brian S O'Neill
+
See Also:
Repository.enterTransaction(IsolationLevel), +Transaction
+

+ +

Enum Constant Summary

+ + + + + + + + + + + + + + + + + + + + + + + +

Enum Constants
Enum Constant and Description
`NONE` + Indicates that no actual transaction is in progress. +
`READ_COMMITTED` + Indicates that dirty reads are prevented. +
`READ_UNCOMMITTED` + Indicates that dirty reads, non-repeatable reads and phantom reads can + occur. +
`REPEATABLE_READ` + Indicates that dirty reads and non-repeatable reads are prevented. +
`SERIALIZABLE` + Indicates that dirty reads, non-repeatable reads and phantom reads are + prevented. +
`SNAPSHOT` + Indicates that dirty reads, non-repeatable reads and phantom reads are + prevented. +

+ +

+ + +

Method Summary

+ + + + + + + + + + + + + + + + + + + + + + + + + + + + + + +

Methods
Modifier and Type	Method and Description
`IsolationLevel`	`highestCommon(IsolationLevel level)` + Returns the highest common isolation level between this and the one + given. +
`boolean`	`isAtLeast(IsolationLevel level)` + Returns true if this isolation level is at least as high as the one + given. +
`boolean`	`isAtMost(IsolationLevel level)` + Returns true if this isolation level is no higher than the one given. +
`IsolationLevel`	`lowestCommon(IsolationLevel level)` + Returns the lowest common isolation level between this and the one + given. +
`static IsolationLevel`	`valueOf(java.lang.String name)` + Returns the enum constant of this type with the specified name. +
`static IsolationLevel[]`	`values()` + Returns an array containing the constants of this enum type, in +the order they are declared. +

+ + +
Methods inherited from class java.lang.Enum
+clone, compareTo, equals, finalize, getDeclaringClass, hashCode, name, ordinal, toString, valueOf

+ + +
Methods inherited from class java.lang.Object
+getClass, notify, notifyAll, wait, wait, wait

+ +
- + + +
  Enum Constant Detail
  + + + +
  - +
    NONE
    +
```
public static final IsolationLevel NONE
```
    +
    Indicates that no actual transaction is in progress. If this level is + specified when entering a transaction, it uses auto-commit mode.
    +
  + + + +
  - +
    READ_UNCOMMITTED
    +
```
public static final IsolationLevel READ_UNCOMMITTED
```
    +
    Indicates that dirty reads, non-repeatable reads and phantom reads can + occur. This level allows modifications by one transaction to be read by + another transaction before any changes have been committed (a "dirty + read"). If any of the changes are rolled back, the second transaction + will have retrieved an invalid modification. + +
    This level is also known as degree 1 isolation.
    +
  + + + +
  - +
    READ_COMMITTED
    +
```
public static final IsolationLevel READ_COMMITTED
```
    +
    Indicates that dirty reads are prevented. Non-repeatable reads and + phantom reads can occur. This level only prohibits a transaction from + reading modifications with uncommitted changes in it. + +
    This level is also known as degree 2 isolation.
    +
  + + + +
  - +
    REPEATABLE_READ
    +
```
public static final IsolationLevel REPEATABLE_READ
```
    +
    Indicates that dirty reads and non-repeatable reads are prevented. + Phantom reads can occur. This level prohibits a transaction from reading + uncommitted changes, and it also prohibits the situation where one + transaction reads a record, a second transaction alters the record, and + the first transaction rereads the record, getting different values the + second time (a "non-repeatable read").
    +
  + + + +
  - +
    SNAPSHOT
    +
```
public static final IsolationLevel SNAPSHOT
```
    +
    Indicates that dirty reads, non-repeatable reads and phantom reads are + prevented. Commits can still fail however, as snapshot isolation avoids + using locks.
    +
  + + + +
  - +
    SERIALIZABLE
    +
```
public static final IsolationLevel SERIALIZABLE
```
    +
    Indicates that dirty reads, non-repeatable reads and phantom reads are + prevented. Phantoms are records returned as a result of a search, but + which were not seen by the same transaction when the identical search + criteria was previously used. For example, another transaction may have + inserted records which match the original search. + +
    This level is also known as degree 3 isolation.
    +
  +
+ +
- + + +
  Method Detail
  + + + +
  - +
    values
    +
```
public static IsolationLevel[] values()
```
    +
    Returns an array containing the constants of this enum type, in +the order they are declared. This method may be used to iterate +over the constants as follows: +
```
+for (IsolationLevel c : IsolationLevel.values())
+    System.out.println(c);
+
```
    +
    Returns:
    an array containing the constants of this enum type, in +the order they are declared
    +
  + + + +
  - +
    valueOf
    +
```
public static IsolationLevel valueOf(java.lang.String name)
```
    +
    Returns the enum constant of this type with the specified name. +The string must match exactly an identifier used to declare an +enum constant in this type. (Extraneous whitespace characters are +not permitted.)
    +
    Parameters:
    name - the name of the enum constant to be returned.
    +
    Returns:
    the enum constant with the specified name
    +
    Throws:
    +
    java.lang.IllegalArgumentException - if this enum type has no constant +with the specified name
    +
    java.lang.NullPointerException - if the argument is null
    +
  + + + +
  - +
    isAtLeast
    +
```
public boolean isAtLeast(IsolationLevel level)
```
    +
    Returns true if this isolation level is at least as high as the one + given.
    +
  + + + +
  - +
    isAtMost
    +
```
public boolean isAtMost(IsolationLevel level)
```
    +
    Returns true if this isolation level is no higher than the one given.
    +
  + + + +
  - +
    lowestCommon
    +
```
public IsolationLevel lowestCommon(IsolationLevel level)
```
    +
    Returns the lowest common isolation level between this and the one + given.
    +
  + + + +
  - +
    highestCommon
    +
```
public IsolationLevel highestCommon(IsolationLevel level)
```
    +
    Returns the highest common isolation level between this and the one + given.
    +
  +
+

Enum IsolationLevel

Enum Constant Summary

Method Summary

Methods inherited from class java.lang.Enum

Methods inherited from class java.lang.Object

Enum Constant Detail

NONE

READ_UNCOMMITTED

READ_COMMITTED

REPEATABLE_READ

SNAPSHOT

SERIALIZABLE

Method Detail

values

valueOf

isAtLeast

isAtMost

lowestCommon

highestCommon