LogicalWindow is used internally. If you write a query with a windowed aggregate (say “SELECT SUM(x) OVER …”) it is converted to LogicalProject, which is converted by ProjectToWindowRule to a LogicalWindow, which is converted by other rules to a physical operator such as EnumerableWindow.
Initially we allow windowed aggregates (represented as RexOver) to be mixed in with other expressions in LogicalProject (just like in a SELECT clause) but later we segregate windowed aggregates into LogicalWindow. This means that other planner rules don’t have to worry about tripping up on a type of expression they don’t understand. Julian > On May 27, 2016, at 7:02 PM, Zhangrucong <[email protected]> wrote: > > Hi Julian: > Thank you very much for your reply. > > My question is this: > In the calcite code，there is a LogicalWindow. When to use it? > > I have another question, for window syntax, RANGE > numericOrIntervalExpression { PRECEDING | FOLLOWING }. How to understand > flowing for stream? Can you give me a example? > > Thanks in advance! > > > -----邮件原件----- > 发件人: Julian Hyde [mailto:[email protected]] > 发送时间: 2016年5月28日 8:51 > 收件人: [email protected] > 主题: Re: Some questions > > HepPlanner is a rule-based planner that applies a small set of rules in a > particular order to every relational expression in a tree. It is generally > used for quick once-over rewrites. > > VolcanoPlanner is a cost-based planner that applies all rules, generates new > relational expressions, and then keeps on firing the rules until nothing else > matches. It is easier to use (you don't have to specify which order the rules > will be applied) but it can be expensive, especially on complex queries, > because it is exhaustive. > > I recommend using VolcanoPlanner at first, then use a hybrid strategy when > you need to deal with complex queries (e.g. queries with more than about 6 > joins). > > I don't understand your question 2. Can you give an example of a query and > the plan it produces? > > Julian > > > > On Thu, May 26, 2016 at 11:23 PM, Zhangrucong <[email protected]> wrote: >> Hello everyone: >> >> Now I am learning calcite streamSQL. I have two questions. Anyone can help >> me. Thanks in advance. >> >> The questions are following: >> >> 1、 what is the difference between HepPlanner and VolcanoPlanner? For >> streamSQL ,which one is better? Are there have some materials to introduce >> two models? >> >> 2、 In the logic plan tree, window is combined with aggregate node or >> expression node. In which case, there is a lonely window node in logic plan?
