Sliding windows are so different from tumbling windows that it doesn’t make sense to give them a “window key”. With sliding windows, every row has its own window. So, given a row R you determine what rows are in R’s window based on its windowing criteria, e.g. “rows between 5 preceding and 5 following partition by productId”, or “order by rowtime range ‘1’ minute preceding”.
There is no instantaneous flush of a hash table, as occurs in tumbling windows. Julian On May 5, 2015, at 4:04 PM, Yi Pan <nickpa...@gmail.com> wrote: > Hi, Julian, > > Great! I am looking forward to it. Could you help to answer my question > regarding to the sliding windows in the previous email? > > Thanks a lot! > > -Yi > > On Tue, May 5, 2015 at 10:46 AM, Julian Hyde <jul...@hydromatic.net> wrote: > >> >> On May 4, 2015, at 10:52 AM, Yi Pan <nickpa...@gmail.com> wrote: >> >>> Just one observation that I wanted to add in: I noted that actually any >>> range-based query clause on an ordered stream essentially means the need >>> for a windowing method in the ordered stream scan. Is it possible to >>> identify a common syntax expression from the query parser in Calcite for >>> any range-based clauses on a StreamScan operator and extract the window >>> spec like: >>> LogicalProject(...) >>> StreamScan(table=[[STREAMS, ORDERS]], fields=[[0,1,2,3]]) >>> >>> To: >>> LogicalProject(...) >>> LogicalWindow(<WindowSpec from the range defining expression in >>> LogicalProject>) >>> StreamScan(table=[[STREAMS, ORDERS]], fields=[[0,1,2,3]]) >> >> Yes, I plan to do this. >> >> Calcite treats LogicalWindow is a bit differently from the other logical >> operators. A query that contains a windowed aggregate such as “SUM(units) >> OVER <window>” is first translated to a LogicalProject that contains >> windowed aggregates as if they were ordinary function calls, then >> ProjectToWindowRule converts that LogicalProject to a LogicalWindow. >> >> But by the time Samza sees the relational expressions you can assume that >> all windowed aggregates have been moved into a LogicalWindow. >> >> I have logged https://issues.apache.org/jira/browse/CALCITE-713. >> >> Julian >> >>
