Which planner you use is generally going to depend on your goal in using the optimizer. HepPlanner applies a given list of optimization rules until none of those rules are applicable. VolcanoPlanner tries to estimate the cost of executing a query and explores applying different rules in an attempt to minimize this cost.
-- Michael Mior mm...@apache.org Le mer. 29 août 2018 à 15:21, Z. S. <zilvinas.sal...@gmail.com> a écrit : > Hi, > > I've been struggling to figure out how to do a very simple thing with > calcite. Hook it to a database, pass a query to a query planner and get > optimization rules applied to it. > > I couldn't find any documentation that shows start to end how to enable > some rule and get a query optimized. What we've been able to do so far is > to get a logical plan from calcite doing somehting like this: > > SqlNode sqlNode = planner.parse(query); > SqlNode validatedSqlNode = planner.validate(sqlNode); > RelRoot rel = planner.rel(validatedSqlNode); > RelNode project = rel.project(); > > We then create a HepPlanner and call findBestExp. I saw that Hive project > is doing something very similar here: > > https://github.com/apache/hive/blob/198487557d17d53fa9216a3e814b7eb073da4781/ql/src/java/org/apache/hadoop/hive/ql/parse/CalcitePlanner.java#L1843 > > But is it required to use HepPlanner? I see that once I call > planner.rel(validatedSqlNode) that the resulting RelNode already has a > volcanoPlanner attached. How do I actually apply some optimization rules to > it? A fully working example would be appreciated and something that would > be very useful on the documentation pages. > > Thanks a lot for any help with this. >
