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We would like to propose 4 kinds of window TVF: tumbling, hopping, cumulative, session. The return value of window TVF is a relation that includes all columns of data as well as additional one column named window
to indicate the assigned window. The window column is a composite ROW
type consists of 3 columns named window_start, window_end
and , window_time
columns. The to indicate the assigned window. The window_time
field is a time attribute of the record after window TVF, it alwsays equal to "window_end - 1"
.
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The table-valued function TUMBLE
assigns a window for each row of a relation based on a time attribute column. The return value of TUMBLE
is a relation that includes all columns of data as well as additional a ROW
type column named window
to 3 columns named window_start, window_end, window_time
to indicate the assigned window. The original row time attribute "timecol" will be a regular timestamp column after window TVF. All assigned windows have the same length, and that’s why tumbling sometimes is named as “fixed windowing”.
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The table-valued function HOP
assigns windows that cover rows within the interval of size and shifting every slide based on a timestamp column. The return value of HOP
is a relation that includes all columns of data as well as additional a ROW
type column named window
additional 3 columns named window_start, window_end, window_time
to indicate the assigned window. The original row time attribute "timecol" will be a regular timestamp column after window TVF. Windows assigned could have overlapping so hopping sometime is named as “sliding windowing”.
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The table-valued function CUMULATE
assigns windows that cover rows within an initial interval of step size, and expanding to one more step size (keep window start fixed) every step until to the max window size. The return value of CUMULATE
is a relation that includes all columns of data as well as additional a ROW
type column named window
3 columns named window_start, window_end, window_time
to indicate the assigned window. The original row time attribute "timecol" will be a regular timestamp column after window TVF. Windows assigned could have overlapping.
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The table-valued function SESSION
assigns windows that cover rows based on datetime. Within a session window, distances of rows are less than interval. Session window is applied per key. The return value of SE
is a relation that includes all columns of data as well as additional a ROW
type column named window
additional 3 columns named window_start, window_end, window_time
to indicate the assigned window. The original row time attribute "timecol" will be a regular timestamp column after window TVF.
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