wip: drl executor

1 files changed, 25 insertions, 0 deletions

diff --git a/lib/drl/ast.ml b/lib/drl/ast.ml
new file mode 100644
index 0000000..f94965d
--- /dev/null
+++ b/lib/drl/ast.ml
@@ -0,0 +1,25 @@
+open Sexplib.Std
+
+(** Literal values for Const nodes *)
+type value =
+  | Int   of int
+  | Float of float
+  | Str   of string
+  | Bool  of bool
+[@@deriving sexp]
+
+type direction = Asc | Desc
+[@@deriving sexp]
+
+type query =
+  | Base    of string                          (** base relation by name *)
+  | Const   of (string * value) list           (** constant single-tuple relation *)
+  | Select  of query * query                   (** σ semijoin: (filter, source) *)
+  | Join    of string list * query * query     (** ⋈ natural equijoin on named attrs *)
+  | Cartesian of query * query                 (** × Cartesian product *)
+  | Project of string list * query             (** π restrict columns *)
+  | Rename  of (string * string) list * query  (** ρ rename (old,new) pairs *)
+  | Union   of query * query                   (** ∪ — compatible schemas assumed *)
+  | Diff    of query * query                   (** − *)
+  | Take    of int * query                     (** τ *)
+[@@deriving sexp]