Aggregate Operator:
Tuple-Based Dimension Options
With a tuple-based dimension, a new window is established and evaluated based on the
number of arriving tuples. For example, a tuple containing the results of the
aggregation is emitted and the window closed when it contains a specified number of
tuples.
The following table describes the options available in the Edit Dimension dialog for
tuple-based dimensions.
TYPE = TUPLE
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Category
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Options and Meaning
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Opening policy:
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Select one of these options:
-
Do not open window based on this
dimension: When selected, this dimension cannot cause the
opening of a new window for the Aggregate.
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Open per Advance: Specify an integer
number of tuples that will cause a new window to open. Think of this
setting as a slider for multiple sliding
windows.
It is a typechecking error to try to specify a value of Advance greater than the value of Window size.
The Offset option is disabled for
tuple-based Aggregates, because each window is simply populated by a
given number of tuples, rather than sets of tuples based on a field's
value or arrival time.
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Window size:
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Select one of these options:
-
Do not close window based on this
dimension: When selected, this dimension cannot cause the
closing of a new window for the Aggregate. If a new window is never
opened, and Do not close is selected,
this creates an infinite sized window that never closes for the life
of the StreamBase Server instance.
-
Close and emit after [number] tuples:
Specify an integer number of tuples that defines the size of each
window. When this number of tuples is exceeded, the window is closed
and an aggregation results tuple is emitted.
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Emission policy:
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Select one of these options:
-
No intermediate emissions based on this
dimension: When selected, this dimension does not force an
immediate emission of a results tuple.
-
Intermediate emission every [number]
tuples: When selected, allows tuples to be emitted before the
window closes. For example, you could emit a results tuple for every
second tuple that arrives within a 30-tuple window, instead of
waiting for 30 tuples to arrive and produce a close event.
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Optional windows:
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For tuple-based aggregates, the only available option in this section is
Create partial windows.
When this check box is cleared (the default setting), the first window is
not created until the specified Window size
is reached, and the operator emits tuples only when windows meet the
criteria above.
Selecting this check box only has an effect when the Advance value is less than the Window size value. In this case, the results depend on
whether you specify any group-by fields in the Group
Options tab:
-
With no grouping specified, this option's effect is to open the first
window immediately and begin to accumulate any tuples that arrive
before the Window size is reached. One
or more extra tuples are emitted at the beginning.
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With groups specified, this option's effect is to open the first
window immediately as above, and to emit extra tuples for partial,
intermediate windows.
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