[15721] Query Rewrite

[zhaoguoquan94]

This PR adds support for query rewriting optimizations that are oblivious to the cost model in Peloton.

• Transitive predicates (optimized in OptimizeLoop)
• Constant folding (optimized in PostgresParser).

We implement query rewrite rules using the current optimizer framework:

• Transitive predicates: we implemented this rule by adding a new step to the beginning OptimizerLoop using a TopDownRewriter. We added rules to take predicates from nodes, generating all possible predicates by taking a transitive closure and add the new ones;

• Trivial predicate simplification: we used the same framework as in the transitive predicates rewrite. This method removes trivial predicates like a = a, some of which are generated by the transitive predicates rule;

Constant folding can transform queries like select * from table where t.column1 = 3*(2-1) to select * from table where t.column1 = 3. These transformation are done in parser level instead of optimizer level because of implementation simplicity. And we don't really lose any information. It support 3 type of constant folding

1. Operators like +-*/
2. Comparison operators like >=, NOT, is null,
3. Conjunctions : AND OR.

[apavlo]

Closing. We will have @Zeninma build this in the fall with a proper rewrite layer.