Optimizer

Cost model

For each plan we keep the following information

• a set of flat query nodes
• a set of unflat query nodes
• one cardinality for all flat query nodes
• one extension rate for each unflat query nodes

We consider the cost of following operator

• EXTEND cost = cardinality of bound node
• FLATTEN cost = cardinality of flatten node

For FILTER, unless it a equal comparsion on primary key, we assume nothing gets filtered by default.