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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]
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