Externalize test cases.
Fix distinct/all default on union/intersect/except
Add/rename a few readers on nodes.
Replace Nadic/nadic? by SetOperator/set_operator?, dyadic
Moved Cog#rewrite inside the compiler itself
Fix SemiJoin when set operators are involved.
Delegate other query methods from with_exp to select_exp
Avoid 'select *' without from_clause.
Comment compilation of summarize for now.
Fix bench, only run tests on sql-izable queries.
Refactor to use Alf::Test tools.
Simplify test infrastructure.
Add flattener of common table expressions.
Fix compilation of multiple joins.
Gemfile on adequate repos.