com.orientechnologies.orient.core.metadata.function

Class ODatabaseFunction

java.lang.Object

com.orientechnologies.orient.core.metadata.function.ODatabaseFunction

All Implemented Interfaces:

OSQLFunction

public class ODatabaseFunction
extends Object
implements OSQLFunction

Dynamic function factory bound to the database's functions

Author:

Luca Garulli

Constructor Summary

Constructors

Constructor and Description
ODatabaseFunction(OFunction f)

Method Summary

Modifier and Type	Method and Description
boolean	aggregateResults() A function can make calculation on several records before returning a result.
void	config(Object[] configuredParameters) Configure the function.
Object	execute(Object iThis, OIdentifiable iCurrentRecord, Object iCurrentResult, Object[] iFuncParams, OCommandContext iContext) Process a record.
boolean	filterResult() A function can act both as transformation or filtering records.
int	getMaxParams() Maximum number of parameter this function can handle.
int	getMinParams() Minimum number of parameter this function must have.
String	getName() Function name, the name is used by the sql parser to identify a call this function.
Object	getResult() Only called when function aggregates results after all records have been passed to the function.
String	getSyntax() Returns a convinient SQL String representation of the function.
Object	mergeDistributedResult(List<Object> resultsToMerge) This method correspond to distributed query execution
void	setResult(Object iResult) Called by OCommandExecutor, given parameter is the number of results.
boolean	shouldMergeDistributedResult() This method correspond to distributed query execution

Methods inherited from class java.lang.Object

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

Constructor Detail

ODatabaseFunction

public ODatabaseFunction(OFunction f)

Method Detail

execute

public Object execute(Object iThis,
                      OIdentifiable iCurrentRecord,
                      Object iCurrentResult,
                      Object[] iFuncParams,
                      OCommandContext iContext)

Description copied from interface: OSQLFunction

Process a record.

Specified by:

execute in interface OSQLFunction

iCurrentRecord - : current record

iCurrentResult - TODO

iFuncParams - : function parameters, number is ensured to be within minParams and maxParams.

iContext - : object calling this function

Returns:

function result, can be null. Special cases : can be null if function aggregate results, can be null if function filter results : this mean result is excluded

aggregateResults

public boolean aggregateResults()

Description copied from interface: OSQLFunction

A function can make calculation on several records before returning a result.

Example of such function : sum, count, max, min ...

The final result of the aggregation is obtain by calling OSQLFunction.getResult()

Specified by:

aggregateResults in interface OSQLFunction

Returns:

true if function aggregate results

filterResult

public boolean filterResult()

Description copied from interface: OSQLFunction

A function can act both as transformation or filtering records. If the function may reduce the number final records than it must return true.

Function should return null for the execute method if the record must be excluded.

Specified by:

filterResult in interface OSQLFunction

Returns:

true if the function acts as a record filter.

getName

public String getName()

Description copied from interface: OSQLFunction

Function name, the name is used by the sql parser to identify a call this function.

Specified by:

getName in interface OSQLFunction

Returns:

String , function name, never null or empty.

getMinParams

public int getMinParams()

Description copied from interface: OSQLFunction

Minimum number of parameter this function must have.

Specified by:

getMinParams in interface OSQLFunction

Returns:

minimum number of parameters

getMaxParams

public int getMaxParams()

Description copied from interface: OSQLFunction

Maximum number of parameter this function can handle.

Specified by:

getMaxParams in interface OSQLFunction

Returns:

maximum number of parameters ??? -1 , negative or Integer.MAX_VALUE for unlimited ???

getSyntax

public String getSyntax()

Description copied from interface: OSQLFunction

Returns a convinient SQL String representation of the function.

Example :

  myFunction( param1, param2, [optionalParam3])
 

This text will be used in exception messages.

Specified by:

getSyntax in interface OSQLFunction

Returns:

String , never null.

getResult

public Object getResult()

Description copied from interface: OSQLFunction

Only called when function aggregates results after all records have been passed to the function.

Specified by:

getResult in interface OSQLFunction

Returns:

Aggregation result

setResult

public void setResult(Object iResult)

Description copied from interface: OSQLFunction

Called by OCommandExecutor, given parameter is the number of results. ??? strange ???

Specified by:

setResult in interface OSQLFunction

config

public void config(Object[] configuredParameters)

Description copied from interface: OSQLFunction

Configure the function.

Specified by:

config in interface OSQLFunction

shouldMergeDistributedResult

public boolean shouldMergeDistributedResult()

Description copied from interface: OSQLFunction

This method correspond to distributed query execution

Specified by:

shouldMergeDistributedResult in interface OSQLFunction

Returns:

true if results that comes from different nodes need to be merged to obtain valid one, false otherwise

mergeDistributedResult

public Object mergeDistributedResult(List<Object> resultsToMerge)

Description copied from interface: OSQLFunction

This method correspond to distributed query execution

Specified by:

mergeDistributedResult in interface OSQLFunction

Parameters:

resultsToMerge - is the results that comes from different nodes

Returns:

is the valid merged result