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Looking for help on query optimization statistics


I'm working on comparing the query plan generated by Calcite with that from a DBMS I'm developing.

In particular, I can generate some TPC-H data and a SQL query, and I want to let Calcite generate as good query plan as it can. So far, I haven't passed any statistics to Calcite, so the query plan it generates is just a baseline. 

Now I wonder how I could pass statistics to Calcite. What I don't understand is that since Calcite does not load the data until query plan is actually executed, how could I pass statistics to it?
I fail to find any document talking about how to do that in detail. The last paragraphs of  http://calcite.apache.org/docs/adapter.html do mention it but are not so clear. 

Would you please help me?

Thanks a lot.

Tian Ye