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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 do mention it but are not so clear. 

Would you please help me?

Thanks a lot.

Tian Ye