Package org.h2.mvstore

Class MVMap.DecisionMaker<V>

java.lang.Object

org.h2.mvstore.MVMap.DecisionMaker<V>

Type Parameters:

V - value type of the map

Enclosing class:

MVMap<K,V>

public abstract static class MVMap.DecisionMaker<V>
extends java.lang.Object

Class DecisionMaker provides callback interface (and should become a such in Java 8) for MVMap.operate() method. It provides control logic to make a decision about how to proceed with update at the point in execution when proper place and possible existing value for insert/update/delete key is found. Revised value for insert/update is also provided based on original input value and value currently existing in the map.

Constructor Summary

Constructors

Constructor	Description
DecisionMaker()

Method Summary

Modifier and Type	Method	Description
<K> CursorPos<K,V>	decide(CursorPos<K,V> tip, K key, V providedValue)	Makes a page-level decision about how to proceed with the operation.
abstract MVMap.Decision	decide(V existingValue, V providedValue)	Makes a decision about how to proceed with the update.
MVMap.Decision	decide(V existingValue, V providedValue, CursorPos<?,?> tip)	Makes entry-level decision about how to proceed with the update.
static <V> MVMap.DecisionMaker<V>	defaultDecision()	Decision maker for transaction rollback.
static <V> MVMap.DecisionMaker<V>	ifAbsentDecision()	Decision maker for putIfAbsent() key/value.
static <V> MVMap.DecisionMaker<V>	ifPresentDecision()	Decision maker for replace().
void	onPageReplaced()	DecisionMaker gets notified when proposed updated page was successfully injected into the B-tree to provide opportunity for internal state maintenance.
static <V> MVMap.DecisionMaker<V>	putDecision()	Decision maker for put().
static <V> MVMap.DecisionMaker<V>	removeDecision()	Decision maker for remove().
void	reset()	Resets internal state (if any) of this DecisionMaker to it's initial state.
<T extends V> T	selectValue(T existingValue, T providedValue)	Provides revised value for insert/update based on original input value and value currently existing in the map.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

DecisionMaker

public DecisionMaker()

Method Detail

defaultDecision

public static <V> MVMap.DecisionMaker<V> defaultDecision()

Decision maker for transaction rollback.

Type Parameters:

V - value type of the map

Returns:

decision maker

putDecision

public static <V> MVMap.DecisionMaker<V> putDecision()

Decision maker for put().

Type Parameters:

V - value type of the map

Returns:

decision maker

removeDecision

public static <V> MVMap.DecisionMaker<V> removeDecision()

Decision maker for remove().

Type Parameters:

V - value type of the map

Returns:

decision maker

ifAbsentDecision

public static <V> MVMap.DecisionMaker<V> ifAbsentDecision()

Decision maker for putIfAbsent() key/value.

Type Parameters:

V - value type of the map

Returns:

decision maker

ifPresentDecision

public static <V> MVMap.DecisionMaker<V> ifPresentDecision()

Decision maker for replace().

Type Parameters:

V - value type of the map

Returns:

decision maker

decide

public <K> CursorPos<K,V> decide(CursorPos<K,V> tip,
                                       K key,
                                       V providedValue)

Makes a page-level decision about how to proceed with the operation. This default implementation delegates decision to entry-level call decide(Object, Object, CursorPos)

Type Parameters:

K - type of the key

Parameters:

tip - path from the leaf page, which is targeted by this operation - contains specified key or holds it's position

key - for the operation

providedValue - value for the operation

Returns:

up to three attributes, which are contained within CursorPos object. Possible values are:

• null, if operation should be re-tried;
• original tip, if operation should be aborted without any changes;
• path from an updated page to tree root, where index attribute (irrelevant in this context) is reused as memory size adjustment for an updated page;

decide

public MVMap.Decision decide(V existingValue,
                             V providedValue,
                             CursorPos<?,?> tip)

Makes entry-level decision about how to proceed with the update.

Parameters:

existingValue - the old value

providedValue - the new value

tip - the cursor position

Returns:

the decision

decide

public abstract MVMap.Decision decide(V existingValue,
                                      V providedValue)

Makes a decision about how to proceed with the update.

Parameters:

existingValue - value currently exists in the map

providedValue - original input value

Returns:

PUT if a new value need to replace existing one or a new value to be inserted if there is none REMOVE if existing value should be deleted ABORT if update operation should be aborted or repeated later REPEAT if update operation should be repeated immediately

selectValue

public <T extends V> T selectValue(T existingValue,
                                   T providedValue)

Provides revised value for insert/update based on original input value and value currently existing in the map. This method is only invoked after call to decide(), if it returns PUT.

Type Parameters:

T - value type

Parameters:

existingValue - value currently exists in the map

providedValue - original input value

Returns:

value to be used by insert/update

reset

public void reset()

Resets internal state (if any) of this DecisionMaker to it's initial state. This method is invoked whenever concurrent update failure is encountered, so we can re-start update process.

onPageReplaced

public void onPageReplaced()

DecisionMaker gets notified when proposed updated page was successfully injected into the B-tree to provide opportunity for internal state maintenance.