Package com.inductiveautomation.historian.gateway.query.execution

Class AggregateHistoryQueryExecutor

java.lang.Object

com.inductiveautomation.historian.gateway.query.execution.AggregateHistoryQueryExecutor

All Implemented Interfaces:

HistoryQueryExecutor, Comparator<HistoryQueryExecutor>

public class AggregateHistoryQueryExecutor
extends Object
implements HistoryQueryExecutor, Comparator<HistoryQueryExecutor>

This class is an aggregate history query executor. It will take a list of history query executors, and execute them in order. It will always execute the one with the lowest timestamp first. If two executors have the same timestamp, the one that has more data will be executed first. This class is useful for combining multiple history queries into one, and ensuring that the data is returned in the correct order. This is used to combine the history queries for the different providers into one query.

Constructor Summary

Constructors

Constructor	Description
AggregateHistoryQueryExecutor(Collection<? extends HistoryQueryExecutor> allLoaders, List<ResultNode> nodes)

Method Summary

Modifier and Type	Method	Description
int	compare(HistoryQueryExecutor o1, HistoryQueryExecutor o2)
static HistoryQueryExecutor	create(List<HistoryQueryExecutor> executors, List<ResultNode> nodes)	Convenience function that will create an aggregate executor if necessary, or return the single passed in executor if the list size is 1.
protected HistoryQueryExecutor	current()
void	endReading()	If startReading was called, this function must be called (that is, it should be in a finally block).
List<? extends ResultNode>	getColumnNodes()	Returns the HistoryNodes of this executor.
int	getEffectiveWindowSizeMS()	In this context, returns the minimum of the sub-loaders rates.
boolean	hasMore()	Returns TRUE if there is more data available to be written on call to processData()
void	initialize()	Initializes the query, performing any actions necessary to get the information required to run the query.
long	nextTime()	The timestamp of the next value.
long	processData()	Puts the next value(s) into the appropriate column, returning the latest timestamp loaded, or -1 if no data was loaded.
protected void	sort()	This ensures the the next loader to read from is in the head spot.
void	startReading()	Begins reading data.

Methods inherited from class java.lang.Object

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

Methods inherited from interface java.util.Comparator

equals, reversed, thenComparing, thenComparing, thenComparing, thenComparingDouble, thenComparingInt, thenComparingLong

Constructor Details

AggregateHistoryQueryExecutor

public AggregateHistoryQueryExecutor(Collection<? extends HistoryQueryExecutor> allLoaders,
 List<ResultNode> nodes)

Method Details

create

public static HistoryQueryExecutor create(List<HistoryQueryExecutor> executors,
 List<ResultNode> nodes)

Convenience function that will create an aggregate executor if necessary, or return the single passed in executor if the list size is 1. Since we must maintain the order of the history nodes, the sorted list must be passed in as well.

current

protected HistoryQueryExecutor current()

getColumnNodes

public List<? extends ResultNode> getColumnNodes()

Description copied from interface: HistoryQueryExecutor

Returns the HistoryNodes of this executor. There MUST be one for every tag path, and they must be in the same order as the paths provided to the executor when it was created. Also, these values must be available as soon as the executor is created. However, they won't be consulted for their data type until after initialize is called, so the normal procedure is to create and return DelegatingResultNodes, which get filled in later.

Specified by:

getColumnNodes in interface HistoryQueryExecutor

getEffectiveWindowSizeMS

public int getEffectiveWindowSizeMS()

In this context, returns the minimum of the sub-loaders rates.

Specified by:

getEffectiveWindowSizeMS in interface HistoryQueryExecutor

initialize

public void initialize()
                throws Exception

Description copied from interface: HistoryQueryExecutor

Initializes the query, performing any actions necessary to get the information required to run the query.

Specified by:

initialize in interface HistoryQueryExecutor

Throws:

Exception

startReading

public void startReading()
                  throws Exception

Description copied from interface: HistoryQueryExecutor

Begins reading data. IMPORTANT: endReading should always be called at some point after calling startReading.

Specified by:

startReading in interface HistoryQueryExecutor

Throws:

Exception

endReading

public void endReading()

Description copied from interface: HistoryQueryExecutor

If startReading was called, this function must be called (that is, it should be in a finally block).

Specified by:

endReading in interface HistoryQueryExecutor

hasMore

public boolean hasMore()

Description copied from interface: HistoryQueryExecutor

Returns TRUE if there is more data available to be written on call to processData()

Specified by:

hasMore in interface HistoryQueryExecutor

processData

public long processData()
                 throws Exception

Description copied from interface: HistoryQueryExecutor

Puts the next value(s) into the appropriate column, returning the latest timestamp loaded, or -1 if no data was loaded.

Specified by:

processData in interface HistoryQueryExecutor

Throws:

Exception

nextTime

public long nextTime()

Description copied from interface: HistoryQueryExecutor

The timestamp of the next value. -1 if no value is available.

Specified by:

nextTime in interface HistoryQueryExecutor

sort

protected void sort()

This ensures the the next loader to read from is in the head spot. It's also relatively inefficient right now. All we really need to do is push the head down until its ts > elem.timestamp

compare

public int compare(HistoryQueryExecutor o1,
 HistoryQueryExecutor o2)

Specified by:

compare in interface Comparator<HistoryQueryExecutor>