Read_Data_API.rst

API calls for Reading Data

FindDistinctValue()

Searches for data in a stream using the specified search mode. Null is returned if the data is not found. The mode parameter determines how the search for data is executed, as shown in the following table:

Search Mode	Enumeration Value	Action
Exact	1	Returns data if found at the index, otherwise returns null
ExactOrNext	2	Returns data if found at the index or searches forward for the next index with data
ExactOrPrevious	3	Returns data if found at the index or searches for the first previous index with data
Next	4	Searches forward (immediately after the index given) for the next index with data
Previous	5	Searches for the first previous index with data starting immediately behind the index given

Syntax

T FindDistinctValue<T>(string tenantId, string namespaceId, string streamId, string index, QiSearchMode mode);
T FindDistinctValue<T, T1>(string tenantId, string namespaceId, string streamId, T1 index, QiSearchMode mode);
T FindDistinctValue<T, T1, T2>(string tenantId, string namespaceId, string streamId, Tuple<T1, T2> index, QiSearchMode)
Task<T> FindDistinctValueAsync<T>(string tenantId, string namespaceId, string streamId, string index, QiSearchMode mode);
Task<T> FindDistinctValueAsync<T, T1>(string tenantId, string namespaceId, string streamId, T1 index, QiSearchMode mode);
Task<T> FindDistinctValueAsync<T, T1, T2>(string tenantId, string namespaceId, string streamId, Tuple<T1, T2> index, QiSearchMode mode);

Http GET Qi/{tenantId}/{namespaceId}/Streams/{streamId}/Data/FindDistinctValue?index={index}&mode={mode}

Parameters

string tenantID

The tenant identifier for the request

string namespaceId

The namespace identifier for the request

streamId

The stream identifier for the request.

index

The string representation of the index value at which to search.

mode

The search mode (see Operation below).

Optional parameters

None

Returns

A QiStream object

Security

Allowed by administrator and user accounts

Examples

Assume a type named TestType has been created (with a DateTime index parameter named TimeId and a double data parameter called Value). Assume that the stream identified by streamId was created with TestType.

The following example obtains the most recent event in the stream by starting at the index Now and searching backwards until a value is found. Note that if the stream is empty a null is returned in readEvent:

searchMode = QiSearchMode.ExactOrPrevious;
string index = DateTime.Now.ToString(“o”);
var  readEvent = _service.FindDistinctValue<TestType>(namespaceId, streamId, index, searchMode);

The next example does the same thing as the previous example, while illustrating the use of the generic overload allowing DateTime to be used directly as the index instead of a string:

searchMode = QiSearchMode.ExactOrPrevious;
DateTime indexDT = DateTime.Now;
var  readEvent = _service.FindDistinctValue<TestType, DateTime>(namespaceId, streamId, indexDT, searchMode);

The next example uses tuples to indicate the index. Using tuples is useful for stream types with a compound index, such as a DateTime and an Integer.

searchMode = QiSearchMode.ExactOrPrevious;
var tupleId = new Tuple<DateTime, int>(DateTime.Now, 0);
var  readEvent = _service.FindDistinctValue<TestType, DateTime, int>(namespaceId, streamId, tupleId, searchMode);

GetDistinctValue()

Returns an event from the specified stream at the specified index. An exception is thrown if no event exists at the index.

Syntax

T GetDistinctValue<T>(string tenantId, string namespaceId, string streamId, string index);
T GetDistinctValue<T, T1>(string tenantId, string namespaceId, string streamId, T1 index);
T GetDistinctValue<T, T1, T2>(string tenantId, string namespaceId, string streamId, Tuple<T1, T2> index);
Task<T> GetDistinctValueAsync<T>(string tenantId, string namespaceId, string streamId, string index);
Task<T> GetDistinctValueAsync<T, T1>(string tenantId, string namespaceId, string streamId, T1 index);
Task<T> GetDistinctValueAsync<T, T1, T2>(string tenantId, string namespaceId, string streamId, Tuple<T1, T2> index);

Http

GET Qi/{tenantId}/{namespaceId}/Streams/{streamId}/Data/GetDistinctValue?index={index}

Parameters

string tenantID

The tenant identifier for the request

string namespaceId

The namespace identifier for the request

streamId

The stream identifier for the request.

index

A string representation of the index value at which to search.

Optional parameters

None

Returns

A QiStream object

Security

Allowed by administrator and user accounts

Examples The following example obtains the event in the stream at the index defined by Now. An exception is thrown if there is no event at that index:

string index = DateTime.Now.ToString(“o”);
try
{
    var  readEvent = _service.GetDistinctValue<TestType>(namespaceId, streamId, index);
}
Catch (exception e)
{
    //handle exception
}

Overloads

T GetDistinctValue(string tenantId, string namespaceId, string streamId, T1 index);

Can be used to supply the index of the call as a different type.

T GetDistinctValue(string tenantId, string namespaceId, string streamId, Tuple index);

Can be used to supply the index of the call as a tuple (for compound indexes).

See the *FindDistinctValue( )* examples for an illustration of these.

GetFirstValue()

Returns the first data event in the stream. Returns null if the stream has no data (no exception is thrown).

Syntax

T GetFirstValue<T>(string tenantId, string namespaceId, string streamId);
Task<T> GetFirstValueAsync<T>(string tenantId, string namespaceId, string streamId);

Http

GET Qi/{tenantId}/{namespaceId}/Streams/{streamId}/Data/GetFirstValue

Parameters

string tenantID

The tenant identifier for the request

string namespaceId

The namespace identifier for the request.

streamId

The stream identifier for the request.

Optional parameters

None

Returns

An IEnumerable of all behavior objects

Security

Allowed by administrator and user accounts

GetLastValue()

Returns the last data event in the stream. Returns null if the stream has no data (no exception is thrown).

Syntax

T GetLastValue<T>(string tenantId, string namespaceId, string streamId);
Task<T> GetLastValueAsync<T>(string tenantId, string namespaceId, string streamId);

Http

GET Qi/{tenantId}/{namespaceId}/Streams/{streamId}/Data/GetLastValue

Parameters

string tenantID

The tenant identifier for the request

string namespaceId

The namespace identifier for the request

streamId

The stream identifier for the request.

Optional parameters

None

Returns

An IEnumerable of all behavior objects

Security

Allowed by administrator and user accounts

GetRangeValues()

Retrieves events from a stream based on a starting index and a specified number of events. Optionally, you can specify search direction, number of events to skip, special boundary handling for startIndex, and an event filter by using overloads. Events returned by GetRangeValues( ) are stored events, not calculated events, with the exception of the starting event if ExactOrCalculated is specified for boundaryType.

Syntax

Qi Client Library

IEnumerable<T> GetRangeValues<T>(string tenantId, string namespaceId, string streamId, string startIndex, int count);
IEnumerable<T> GetRangeValues<T>(string tenantId, string namespaceId, string streamId, string startIndex, int count, bool reversed);
IEnumerable<T> GetRangeValues<T>(string tenantId, string namespaceId, string streamId, string startIndex, int count, QiBoundaryType boundaryType);
IEnumerable<T> GetRangeValues<T>(string tenantId, string namespaceId, string streamId, string startIndex, int skip, int count, bool reversed, QiBoundaryType boundaryType);
IEnumerable<T> GetRangeValuesAsync<T>(string tenantId, string namespaceId, string streamId, string startIndex, int skip, int count, bool reversed, QiBoundaryType boundaryType, string filterExpression);
Task<IEnumerable<T>> GetRangeValuesAsync<T>(string tenantId, string namespaceId, string streamId, string startIndex, int count);
Task<IEnumerable<T>> GetRangeValuesAsync<T>(string tenantId, string namespaceId, string streamId, string startIndex, int count, bool reversed);
Task<IEnumerable<T>> GetRangeValuesAsync<T>(string tenantId, string namespaceId, string streamId, string startIndex, int count, QiBoundaryType boundaryType);
Task<IEnumerable<T>> GetRangeValuesAsync<T>(string tenantId, string namespaceId, string streamId, string startIndex, int skip, int count, bool reversed, QiBoundaryType boundaryType);
Task<IEnumerable<T>> GetRangeValuesAsync<T>(string tenantId, string namespaceId, string streamId, string startIndex, int skip, int count, bool reversed, QiBoundaryType boundaryType, string filterExpression);

Http

GET Qi/{tenantId}/{namespaceId}/Streams/{streamId}/Data/GetRangeValues?startIndex={startIndex}&count={count}
GET Qi/{tenantId}/{namespaceId}/Streams/{streamId}/Data/GetRangeValues?startIndex={startIndex}&count={count}&reversed={reversed}
GET Qi/{tenantId}/{namespaceId}/Streams/{streamId}/Data/GetRangeValues?startIndex={startIndex}&count={count}&boundaryType={boundaryType}
GET Qi/{tenantId}/{namespaceId}/Streams/{streamId}/Data/GetRangeValues?startIndex={startIndex}&skip={skip}&count={count}&reversed={reversed}&boun GET daryType={boundaryType}
GET Qi/{tenantId}/{namespaceId}/Streams/{streamId}/Data/GetRangeValues?startIndex={startIndex}&skip={skip}&count={count}&reversed={reversed}&boun GET daryType={boundaryType}&filterExpression={filterExpression}
GET Qi/{tenantId}/{namespaceId}/Streams/{streamId}/Data/GetRangeValues?startIndex={startIndex}&count={count}
GET Qi/{tenantId}/{namespaceId}/Streams/{streamId}/Data/GetRangeValues?startIndex={startIndex}&count={count}&reversed={reversed}
GET Qi/{tenantId}/{namespaceId}/Streams/{streamId}/Data/GetRangeValues?startIndex={startIndex}&count={count}&boundaryType={boundaryType}
GET Qi/{tenantId}/{namespaceId}/Streams/{streamId}/Data/GetRangeValues?startIndex={startIndex}&skip={skip}&count={count}&reversed={reversed}&boun GET daryType={boundaryType}
GET Qi/{tenantId}/{namespaceId}/Streams/{streamId}/Data/GetRangeValues?startIndex={startIndex}&skip={skip}&count={count}&reversed={reversed}&boundaryType={boundaryType}&filterExpression={filterExpression}

Parameters

string tenantID

The tenant identifier for the request

string namespaceId

The namespace identifier for the request

streamId

The stream identifier for the request.

startIndex

The string representation of the starting index value.

count

The maximum number of events to return.

reversed

The order of event retrieval; true to retrieve events in reverse order.

skip

The number of events to skip; skipped events are not returned or counted. (Applied after filterExpression. )

boundaryType

Enumeration indicating how to handle boundary events.

filterExpression

A string containing an OData filter expression (see Operation section below).

Optional parameters

None

Returns

An IEnumerable of all behavior objects

Security

Allowed by administrator and user accounts

Notes GetRangeValues( ) searches FORWARD if the reverse parameter is false and reverse if the reverse parameter is true. For overloads that do not include the reverse parameter, the default is forward.

The skip parameter indicates the number of events that the call skips over before it collects events for the response.

BoundaryType has the following possible values: • Exact • ExactOrCalculated • Inside • Outside

The BoundaryType determines how to specify the first value in from the stream starting at the start index. This is also affected by the direction of the method. The table below indicates how the first value is determined for GetRangeValues( ) for a FORWARD search of the BoundaryTypes shown:

Boundary Type	First value obtained
Exact	The first value at or after the startIndex
ExactOrCalculated	If a value exists at the startIndex it is used, otherwise a value is ‘calculated’ according to the Stream Behavior setting
Inside	The first value after the startIndex
Outside	The first value before the startIndex

The table below indicates how the first value is determined for GetRangeValues( ) for a reverse search of the BoundaryTypes shown:

Boundary Type	First value obtained
Exact	The first value at or before the startIndex
ExactOrCalculated	If a value exists at the startIndex it is used, otherwise a value is ‘calculated’ according to the Stream Behavior setting. See the Calculated startIndex topic below.
Inside	The first value before the startIndex
Outside	The first value after the startIndex

The order of execution first determines the direction of the method and the starting event using the BoundaryType. After the starting event is determined, the filterExpression is applied in the direction requested to determine potential return values. Then, skip is applied to pass over the specified number of events, including any calculated events. Finally, events up to the number specified by count are returned.

The filter expression uses OData query language. Most of the query language is supported. More information about OData Filter Expressions can be found in Filter expressions

Calculated startIndex When the startIndex for GetRangeValues( ) lands before, after, or in-between data in the stream, and the ExactOrCalculated boundaryType is used, the stream behavior determines whether an additional calculated event is created and returned in the response.

The table below indicates when an event will be calculated and included in the GetRangeValues( ) response for a startIndex before or after all data in the stream. (This data is for FORWARD search modes):

Stream Behavior Mode	Stream Behavior QiStreamExtrapolation	When start index is before all data	When start index is after all data
Continuous	All	Event is calculated*	Event is calculated*
	None	No event calculated	No event calculated
	Backward	Event is calculated*	No event calculated
	Forward	No event calculated	Event is calculated*
Discrete	All	No event calculated	No event calculated
	None	No event calculated	No event calculated
	Backward	No event calculated	No event calculated
	Forward	No event calculated	No event calculated
ContinuousLeading	All	No event calculated	Event is calculated*
	None	No event calculated	No event calculated
	Backward	No event calculated	No event calculated
	Forward	No event calculated	Event is calculated*
ContinuousTrailing	All	Event is calculated*	No event calculated
	None	No event calculated	No event calculated
	Backward	Event is calculated*	No event calculated
	Forward	No event calculated	No event calculated

*Events is calculated using startIndex and the value of the first event

When the startIndex falls between data:

Stream Behavior Mode	Calculated Event
Continuous	Event is calculated using the index and a value interpolated from the surrounding index values
Discrete	No event calculated
ContinuousLeading	Event is calculated using the index and previous event values
ContinuousTrailing	Event is calculated using the index and next event values

GetValue()

Retrieves a value at the specified index. If there is a value at the index, the call returns that event.

If the specified index is before or after all events, the value returned with that index is determined by the stream behavior (specifically, the stream behavior extrapolation setting).

If the specified index is between events, the event returned is determined by the stream behavior and any behavior overrides.

If the stream contains no data, null is returned regardless of the stream behavior.

Syntax

Qi Client Library

T GetValue<T>(string tenantId, string namespaceId, string streamId, string index);
T GetValue<T, T1>(string tenantId, string namespaceId, string streamId, T1 index);
T GetValue<T, T1, T2>(string tenantId, string namespaceId, string streamId, Tuple<T1, T2> index);
Task<T> GetValueAsync<T>(string tenantId, string namespaceId, string streamId, string index);
Task<T> GetValueAsync<T, T1>(string tenantId, string namespaceId, string streamId, T1 index);
Task<T> GetValueAsync<T, T1, T2>(string tenantId, string namespaceId, string streamId, Tuple<T1, T2> index);

Http

GET Qi/{tenantId}/{namespaceId}/Streams/{streamId}/Data/GetValue?index={index}

Parameters

string tenantID

The tenant identifier for the request

string namespaceId

The namespace identifier for the request.

streamId

The stream identifier for the request.

index

A string representation of the index value for GetValue or IEnumerable of index values requested for GetValues.

Optional parameters

None

Returns

An IEnumerable of all behavior objects

Security

Allowed by administrator and user accounts

Examples The following example obtains the event in the stream at the index defined by Now. If no event exists at that index the result is determined by the stream behavior.

string index = DateTime.Now.ToString(“o”);
try
{
    var  readEvent = _service.GetValue<TestType>(namespaceId, streamId, index);
}
Catch (exception e)
{
    //handle exception
}

Overloads

T GetValue(string tenantId, string namespaceId, string streamId, T1 index);

Can be used to supply the index of the call as a different type

T GetValue(string tenantId, string namespaceId, string streamId, Tuple index);

Can be used to supply the index of the call as a tuple (for compound indexes)

See the *FindDistinctValue( )* examples for an illustration of these.

GetValues()

Returns calculated events at the requested index values in index, or count number of evenly spaced calculated events between startIndex and endIndex.

Syntax

IEnumerable<T> GetValues<T>(string tenantId, string namespaceId, string streamId, IEnumerable<string> index);
IEnumerable<T> GetValues<T, T1>(string tenantId, string namespaceId, string streamId, IEnumerable<T1> index);
IEnumerable<T> GetValues<T, T1, T2>(string tenantId, string namespaceId, string streamId, IEnumerable<Tuple<T1, T2>> index);
IEnumerable<T> GetValues<T>(string tenantId, string namespaceId, string streamId, string filterExpression);
IEnumerable<T> GetValues<T>(string tenantId, string namespaceId, string streamId, string startIndex, string endIndex, int count);
IEnumerable<T> GetValues<T, T1>(string tenantId, string namespaceId, string streamId, T1 startIndex, T1 endIndex, int count);
IEnumerable<T> GetValues<T, T1, T2>(string tenantId, string namespaceId, string streamId, Tuple<T1, T2> startIndex, Tuple<T1, T2> endIndex, int count);
Task<IEnumerable<T>> GetValuesAsync<T>(string tenantId, string namespaceId, string streamId, IEnumerable<string> index);
Task<IEnumerable<T>> GetValuesAsync<T, T1>(string tenantId, string namespaceId, string streamId, IEnumerable<T1> index);
Task<IEnumerable<T>> GetValuesAsync<T, T1, T2>(string tenantId, string namespaceId, string streamId, IEnumerable<Tuple<T1, T2>> index);
Task<IEnumerable<T>> GetValuesAsync<T>(string tenantId, string namespaceId, string streamId, string filterExpression);
Task<IEnumerable<T>> GetValuesAsync<T>(string tenantId, string namespaceId, string streamId, string startIndex, string endIndex, int count);
Task<IEnumerable<T>> GetValuesAsync<T, T1>(string tenantId, string namespaceId, string streamId, T1 startIndex, T1 endIndex, int count);
Task<IEnumerable<T>> GetValuesAsync<T, T1, T2>(string tenantId, string namespaceId, string streamId, Tuple<T1, T2> startIndex, Tuple<T1, T2> endIndex, int count);

Http

GET Qi/{tenantId}/{namespaceId}/Streams/{streamId}/Data/GetValues?startIndex={startIndex}&endIndex={endIndex}&count={count}

Parameters

string tenantID

The tenant identifier for the request

string namespaceId

The namespace identifier for the request.

streamId

The stream identifier for the request.

index

IEnumerable of index values at which to return calculated events.

startIndex

A string representation of the starting index value.

endIndex

A string representation of the ending index value.

count

Number of equally-spaced calculated events to return within the startIndex and endIndex boundaries.

Optional parameters

None

Returns

An IEnumerable of all behavior objects

Security

Allowed by administrator and user accounts

Notes

For GetValues( ) overloads that include a streamId and IEnumberable index, the call behaves like multiple GetValue( ) calls. For the GetValues( ) overloads that include startIndex, endIndex and count, these parameters are used to generate a list of indexes for which to obtain values. Events returned for each index are determined according to the QiStreamBehavior assigned to the stream being read.

For GetValues( ) overloads that include the filterExpression parameters are used to create a list of indexes that match the OData filter text used. More information on OData Filter Expressions can be found in Filter expressions

GetWindowValues()

Returns stored events within a specified index range.

Syntax

Qi Client Library

IEnumerable<T> GetWindowValues<T>(string tenantId, string namespaceId, string streamId, string startIndex, string endIndex);
IEnumerable<T> GetWindowValues<T>(string tenantId, string namespaceId, string streamId, string startIndex, string endIndex, QiBoundaryType boundaryType);
IEnumerable<T> GetWindowValues<T>(string tenantId, string namespaceId, string streamId, string startIndex, string endIndex, QiBoundaryType boundaryType, string filterExpression);
IEnumerable<T> GetWindowValues<T>(string tenantId, string namespaceId, string streamId, string startIndex, QiBoundaryType startBoundaryType, string endIndex, QiBoundaryType endBoundaryType, string filterExpression);
QiResultPage<T> GetWindowValues<T>(string tenantId, string namespaceId, string streamId, string startIndex, string endIndex, QiBoundaryType boundaryType, int count, string continuationToken);
IEnumerable<T> GetWindowValues<T>(string tenantId, string namespaceId, string streamId, string startIndex, QiBoundaryType startBoundaryType, string endIndex, QiBoundaryType endBoundaryType, string filterExpression, string selectExpression);
QiResultPage<T> GetWindowValues<T>(string tenantId, string namespaceId, string streamId, string startIndex, string endIndex, QiBoundaryType boundaryType, string filterExpression, int count, string continuationToken);
Task<IEnumerable<T>> GetWindowValuesAsync<T>(string tenantId, string namespaceId, string streamId, string startIndex, string endIndex);
Task<IEnumerable<T>> GetWindowValuesAsync<T>(string tenantId, string namespaceId, string streamId, string startIndex, string endIndex, QiBoundaryType boundaryType);
Task<IEnumerable<T>> GetWindowValuesAsync<T>(string tenantId, string namespaceId, string streamId, string startIndex, string endIndex, QiBoundaryType boundaryType, string filterExpression);
Task<IEnumerable<T>> GetWindowValuesAsync<T>(string tenantId, string namespaceId, string streamId, string startIndex, QiBoundaryType startBoundaryType, string endIndex, QiBoundaryType endBoundaryType, string filterExpression);
Task<QiResultPage<T>> GetWindowValuesAsync<T>(string tenantId, string namespaceId, string streamId, string startIndex, string endIndex, QiBoundaryType boundaryType, int count, string continuationToken);
Task<IEnumerable<T>> GetWindowValuesAsync<T>(string tenantId, string namespaceId, string streamId, string startIndex, QiBoundaryType startBoundaryType, string endIndex, QiBoundaryType endBoundaryType, string filterExpression, string selectExpression);
Task<QiResultPage<T>> GetWindowValuesAsync<T>(string tenantId, string namespaceId, string streamId, string startIndex, string endIndex, QiBoundaryType boundaryType, string filterExpression, int count, string continuationToken);

Http

GET Qi/{tenantId}/{namespaceId}/Streams/{streamId}/Data/GetWindowValues?startIndex={startIndex}&endIndex={endIndex}
GET Qi/{tenantId}/{namespaceId}/Streams/{streamId}/Data/GetWindowValues?startIndex={startIndex}&endIndex={endIndex}&boundaryType={boundaryType}
GET Qi/{tenantId}/{namespaceId}/Streams/{streamId}/Data/GetWindowValues?startIndex={startIndex}&endIndex={endIndex}&boundaryType={boundaryType}&filterExpression={filterExpression}
GET Qi/{tenantId}/{namespaceId}/Streams/{streamId}/Data/GetWindowValues?startIndex={startIndex}&&endIndex={endIndex}&boundaryType={boundaryType}&count={count}&continuationToken={continuationToken}
GET Qi/{tenantId}/{namespaceId}/Streams/{streamId}/Data/GetWindowValues?startIndex={startIndex}&startBoundaryType={startBoundaryType}&endIndex={endIndex}&endBoundaryType={endBoundaryType}&filterExpression={filterExpression}&selectExpression={selectExpression}
GET Qi/{tenantId}/{namespaceId}/Streams/{streamId}/Data/GetWindowValues?startIndex={startIndex}&&endIndex={endIndex}&boundaryType={boundaryType}&count={count}&continuationToken={continuationToken}

Parameters

string tenantID

The tenant identifier for the request

string namespaceId

The namespace identifier for the request.

streamId

The stream identifier for the request.

startIndex

String representation of the starting index value, must be less than endIndex.

endIndex

String representation of the ending index value.

boundaryType

Enumeration describing how to handle boundary events.

filterExpression

OData filter expression.

count

Maximum of events to return within the specified index range. For paging through data.

continuationToken

Continuation token for handling multiple return data sets.

startBoundaryType

How to handle startIndex boundary events.

endBoundaryType

How to handle endIndex boundary events.

selectExpression

Expression designating which fields of the stream's type should make up the return events.

Optional parameters

None

Returns

An IEnumerable of all behavior objects

Security

Allowed by administrator and user accounts

Notes

If count and continuationToken are used, up to count events are returned within the specified index range along with a continuation token that may be passed into a subsequent GetWindowValues( ) call to obtain the next count events. Note that count need not stay the same through multiple GetWindowValues( ) calls with continuationToken.

Boundary events at or near startIndex and endIndex are handled according to boundaryType or startBoundaryType and endBoundaryType, which have the following possible values: • Exact • ExactOrCalculated • Inside • Outside

The table below indicates how the first value is determined for GetWindowValues ( ) for the startBoundaryType shown:

startBoundaryType	First value obtained
Exact	The first value at or after the startIndex
ExactOrCalculated	If a value exists at the startIndex it is used, else a value is calculated according to the stream's behavior setting
Inside	The first value after the startIndex
Outside	The first value before the startIndex

This chart indicates how the last value is determined for GetWindowValues( ) for the endBoundaryType shown:

endBoundaryType	First value obtained
Exact	The first value at or before the endIndex
ExactOrCalculated	If a value exists at the endIndex it is used, else a value is calculated according to the stream's behavior setting
Inside	The first value before the endIndex
Outside	The first value after the endIndex

Calls against an empty stream always return a single null regardless of boundary type used.

The filter expression uses OData syntax. More information on OData Filter Expressions can be found in Filter expressions

The select expression is a CSV list of strings that indicate which fields of the stream type are being requested. By default all type fields are included in the response. Select may improve the performance of the call by avoiding management of the unneeded fields. Note that the index is always included in the returned results.

Selection is applied before filtering; therefore, any fields that are used in the filter expression must be included by the select statement.

Calculated startIndex and endIndex When the startIndex or endIndex of GetWindowValues( ) does not fall on an event in the stream, and the boundaryType of ExactOrCalculated is used, an event may be created and returned in the GetWindowValues call response.

The table below indicates when a calculated event is created for indexes before or after stream data:

QiStreamBehavior Mode	QiStreamBehavior ExtrapolationMode	When start index is before all data	When start index is after all data
Continuous	All	Event is calculated*	Event is calculated*
	None	No event calculated	No event calculated
	Backward	Event is calculated*	No event calculated
	Forward	No event calculated	Event is calculated*
Discrete	All	No event calculated	No event calculated
	None	No event calculated	No event calculated
	Backward	No event calculated	No event calculated
	Forward	No event calculated	No event calculated
ContinuousLeading	All	No event calculated	Event is calculated*
	None	No event calculated	No event calculated
	Backward	No event calculated	No event calculated
	Forward	No event calculated	Event is calculated*
ContinuousTrailing	All	Event is calculated*	No event calculated
	None	No event calculated	No event calculated
	Backward	Event is calculated*	No event calculated
	Forward	No event calculated	No event calculated

*When a startIndex event is calculated, the created event has the startIndex and the value of the first data event in the stream. When an endIndex is calculated, the created event uses the endIndex along with the value from the stream’s last data event. Any calculated events are returned along with the result of the GetWindowValues( ) call.

If an index (startIndex or endIndex) in GetWindowValues( ) lands between data in the stream, and the BoundaryT Type is set to ExactOrCalculated, and event is created according to the following table:

Stream Behavior Mode	Calculated Event
Continuous	The event is calculated using the index and a value that is interpolated from the surrounding index values.
Discrete	No event is calculated.
ContinuousLeading	The event is calculated using the index and the previous event values.
ContinuousTrailing	Event is calculated using the index and next event values