| 摘要 |
A new continuous query to a data stream management system (DSMS) may use a silent relation whose source does not provide any heartbeats. During execution of any given operator, the DSMS processes data from one input (“active input”) using its time stamp as if the same time stamp is received from another input whose relation has fallen silent (“empty input”), if one or more predetermined conditions are met. One predetermined condition is that the empty input's operator has all its own inputs silent. And another predetermined condition is that a maximum time stamp that is currently present among all the inputs of the empty input's operator is equal to a time stamp that was last received from these same inputs. When both conditions are met, previously received data from the empty input is time stamped with the same time stamp as the most recently received data from the active input.
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