feat: add JSON type support

bindings/ffi_bindings.ml

@@ -97,6 +97,7 @@ module Types (F: Ctypes.TYPE) = struct
     let date = constant "MYSQL_TYPE_DATE" int
     let datetime = constant "MYSQL_TYPE_DATETIME" int
     let timestamp = constant "MYSQL_TYPE_TIMESTAMP" int
+    let json = constant "MYSQL_TYPE_JSON" int
   end
 
   module Stmt_attr = struct

examples/async/nonblocking_async_example.ml

@@ -77,6 +77,7 @@ let print_row row =
             (M.Time.hour t)
             (M.Time.minute t)
             (M.Time.second t)
+      | `Json j -> printf "%s\n%!" j
       | `Null -> printf "NULL\n%!")
     row
     ();

examples/blocking/blocking_example.ml

@@ -28,6 +28,7 @@ let print_row row =
             (M.Time.hour t)
             (M.Time.minute t)
             (M.Time.second t)
+      | `Json j -> printf "%s\n%!" j
       | `Null -> printf "NULL\n%!")
     row
 

examples/lwt/nonblocking_lwt_example.ml

@@ -63,6 +63,7 @@ let print_row row =
             (M.Time.hour t)
             (M.Time.minute t)
             (M.Time.second t)
+      | `Json j -> Lwt_io.printf "%s\n%!" j
       | `Null -> Lwt_io.printf "NULL\n%!")
     row
     Lwt.return_unit

examples/select/nonblocking_select_example.ml

@@ -66,6 +66,7 @@ let print_row row =
             (M.Time.hour t)
             (M.Time.minute t)
             (M.Time.second t)
+      | `Json j -> printf "%s\n%!" j
       | `Null -> printf "NULL\n%!")
     row;
   return ()

lib/bind.ml

@@ -35,6 +35,7 @@ type buffer_type =
   | `Date
   | `Datetime
   | `Timestamp
+  | `Json
   ]
 
 let buffer_type_of_int i =
@@ -61,6 +62,7 @@ let buffer_type_of_int i =
   else if i = date         then `Date
   else if i = datetime     then `Datetime
   else if i = timestamp    then `Timestamp
+  else if i = json         then `Json
   else invalid_arg @@ "unknown buffer type " ^ (string_of_int i)
 
 let yes = '\001'
@@ -187,3 +189,14 @@ let time b param ~at =
     ~mysql_type:(type_of_time_kind param.Time.kind)
     ~unsigned:no
     ~at
+
+let json b param ~at =
+  let len = String.length param in
+  let p = allocate_n char ~count:len in
+  String.iteri (fun i c -> (p +@ i) <-@ c) param;
+  bind b
+    ~buffer:(coerce (ptr char) (ptr void) p)
+    ~size:len
+    ~mysql_type:T.Type.string
+    ~unsigned:no
+    ~at

lib/common.ml

@@ -338,7 +338,8 @@ module Stmt = struct
             | `Float x -> Bind.float b x ~at
             | `String s -> Bind.string b s ~at
             | `Bytes s -> Bind.blob b s ~at
-            | `Time t -> Bind.time b t ~at)
+            | `Time t -> Bind.time b t ~at
+            | `Json j -> Bind.json b j ~at)
           params;
         if B.mysql_stmt_bind_param stmt.raw b.Bind.bind then
           `Ok stmt
@@ -354,7 +355,7 @@ module Stmt = struct
     | `Int24 | `Long | `Float -> 4
     | `Long_long | `Double -> 8
     | `Decimal | `New_decimal | `String | `Var_string
-    | `Tiny_blob | `Blob | `Medium_blob | `Long_blob | `Bit -> -1
+    | `Tiny_blob | `Blob | `Medium_blob | `Long_blob | `Bit | `Json -> -1
     | `Time | `Date | `Datetime | `Timestamp -> Ctypes.sizeof T.Time.t
 
   let malloc count =

lib/field.ml

@@ -9,6 +9,7 @@ type value =
   | `String of string
   | `Bytes of bytes
   | `Time of Time.t
+  | `Json of string
   ]
 
 type t =
@@ -65,7 +66,7 @@ let to_time field kind =
   ; kind
   }
 
-type to_string = [`Decimal | `New_decimal | `String | `Var_string | `Bit]
+type to_string = [`Decimal | `New_decimal | `String | `Var_string | `Bit | `Json]
 type to_blob   = [`Tiny_blob | `Blob | `Medium_blob | `Long_blob]
 type to_time   = [`Time | `Date | `Datetime | `Timestamp]
 
@@ -85,6 +86,7 @@ let convert field typ unsigned =
   | `Long_long,       false -> `Int (Int64.to_int (cast_to int64_t field))
   | `Float,               _ -> `Float (cast_to float field)
   | `Double,              _ -> `Float (cast_to double field)
+  | `Json,                _ -> `Json (Bytes.to_string (to_bytes field))
   | #to_string,           _ -> `String (Bytes.to_string (to_bytes field))
   | #to_blob,             _ -> `Bytes (to_bytes field)
   | #to_time as t,        _ -> `Time (to_time field t)
@@ -124,6 +126,11 @@ let time field =
   | `Time t -> t
   | _ -> err field ~info:"a time value"
 
+let json field =
+  match value field with
+  | `Json j -> j
+  | _ -> err field ~info:"a json value"
+
 let int_opt field =
   match value field with
   | `Int i -> Some i
@@ -153,3 +160,9 @@ let time_opt field =
   | `Time t -> Some t
   | `Null -> None
   | _ -> err field ~info:"a nullable time value"
+
+let json_opt field =
+  match value field with
+  | `Json j -> Some j
+  | `Null -> None
+  | _ -> err field ~info:"a nullable json value"

lib/mariadb.ml

@@ -33,6 +33,7 @@ module type S = sig
       | `String of string
       | `Bytes of bytes
       | `Time of Time.t
+      | `Json of string
       ]
 
     val name : t -> string
@@ -45,12 +46,14 @@ module type S = sig
     val string : t -> string
     val bytes : t -> bytes
     val time : t -> Time.t
+    val json : t -> string
 
     val int_opt : t -> int option
     val float_opt : t -> float option
     val string_opt : t -> string option
     val bytes_opt : t -> bytes option
     val time_opt : t -> Time.t option
+    val json_opt : t -> string option
   end
 
   module Row : sig

lib/mariadb.mli

@@ -55,6 +55,7 @@ module type S = sig
       | `String of string
       | `Bytes of bytes
       | `Time of Time.t
+      | `Json of string
       ]
 
     val name : t -> string
@@ -85,12 +86,14 @@ module type S = sig
     val string : t -> string
     val bytes : t -> bytes
     val time : t -> Time.t
+    val json : t -> string
 
     val int_opt : t -> int option
     val float_opt : t -> float option
     val string_opt : t -> string option
     val bytes_opt : t -> bytes option
     val time_opt : t -> Time.t option
+    val json_opt : t -> string option
   end
 
   (** A module representing database rows. Rows can be retrieved as different
@@ -401,6 +404,7 @@ module Nonblocking : sig
         | `String of string
         | `Bytes of bytes
         | `Time of Time.t
+        | `Json of string
         ]
 
       val name : t -> string
@@ -413,12 +417,14 @@ module Nonblocking : sig
       val string : t -> string
       val bytes : t -> bytes
       val time : t -> Time.t
+      val json : t -> string
 
       val int_opt : t -> int option
       val float_opt : t -> float option
       val string_opt : t -> string option
       val bytes_opt : t -> bytes option
       val time_opt : t -> Time.t option
+      val json_opt : t -> string option
     end
 
     module Row : sig

lib/nonblocking.ml

@@ -413,6 +413,7 @@ module type S = sig
       | `String of string
       | `Bytes of bytes
       | `Time of Time.t
+      | `Json of string
       ]
 
     val name : t -> string
@@ -425,12 +426,14 @@ module type S = sig
     val string : t -> string
     val bytes : t -> bytes
     val time : t -> Time.t
+    val json : t -> string
 
     val int_opt : t -> int option
     val float_opt : t -> float option
     val string_opt : t -> string option
     val bytes_opt : t -> bytes option
     val time_opt : t -> Time.t option
+    val json_opt : t -> string option
   end
 
   module Row : sig

tests/nonblocking/nonblocking_testsuite.ml

@@ -92,6 +92,7 @@ struct
     | `String s -> sprintf "(%S : string)" s
     | `Bytes s -> sprintf "(%S : bytes)" (Bytes.to_string s)
     | `Time t -> string_of_timestamp t
+    | `Json j -> sprintf "(%S : json)" j
 
   let equal_float x x' =
     abs_float (x -. x') /. (abs_float (x +. x') +. epsilon_float) < 1e-6
@@ -117,6 +118,8 @@ struct
     | `Bytes s, `Bytes s' -> s = s'
     | `Bytes _, _ | _, `Bytes _ -> false
     | `Time t, `Time t' -> equal_time t t'
+    | `Json j, `Json j' -> j = j'
+    | `Json _, _ | _, `Json _ -> false
 
   let assert_field_equal v v' =
     if not (equal_field v v') then begin
@@ -345,10 +348,102 @@ struct
     in
     (test_integer, test_bigint)
 
+  let test_json () =
+    connect () >>= or_die "connect" >>= fun dbh ->
+
+    (* Create a test table with JSON column *)
+    M.prepare dbh
+      "CREATE TEMPORARY TABLE ocaml_mariadb_json_test (id integer PRIMARY KEY AUTO_INCREMENT, data JSON)"
+      >>= or_die "prepare create json table"
+      >>= fun create_table_stmt ->
+    execute_no_data create_table_stmt >>= fun () ->
+
+    (* Test inserting JSON data *)
+    M.prepare dbh "INSERT INTO ocaml_mariadb_json_test (data) VALUES (?)"
+      >>= or_die "prepare insert json"
+      >>= fun insert_stmt ->
+
+    (* Test various JSON types *)
+    let test_cases = [
+      {|{"name": "John", "age": 30}|};
+      {|[1, 2, 3, "four"]|};
+      {|"simple string"|};
+      {|42|};
+      {|true|};
+      {|null|}
+    ] in
+
+    (* Insert all test cases *)
+    iter_s_list (fun json_data ->
+      M.Stmt.execute insert_stmt [| `Json json_data |] >>= or_die "insert json"
+      >|= fun _ -> ()
+    ) test_cases >>= fun () ->
+
+    (* Select and verify we can retrieve JSON data *)
+    M.prepare dbh "SELECT id, data FROM ocaml_mariadb_json_test ORDER BY id"
+      >>= or_die "prepare select json"
+      >>= fun select_stmt ->
+    M.Stmt.execute select_stmt [||] >>= or_die "execute select json" >>= fun res ->
+
+    (* Verify we can fetch and access JSON fields *)
+    let rec verify_rows count =
+      M.Res.fetch (module M.Row.Array) res >>= or_die "fetch json row" >>= function
+      | Some row ->
+          assert (Array.length row = 2);
+          (* Test that we can access the JSON field using different methods *)
+          let json_value = match M.Field.value row.(1) with
+            | `Json j -> j
+            | `String s -> s  (* TiDB/MySQL might return as string *)
+            | _ -> failwith "Expected JSON or String field"
+          in
+          (* Verify we got some data back *)
+          assert (String.length json_value > 0);
+
+          (* Test accessor functions *)
+          let json_direct = M.Field.json row.(1) in
+          let json_opt = M.Field.json_opt row.(1) in
+          assert (json_opt = Some json_direct);
+          assert (String.length json_direct > 0);
+
+          verify_rows (count + 1)
+      | None ->
+          (* We should have retrieved all our test cases *)
+          assert (count = List.length test_cases);
+          return ()
+    in
+
+    verify_rows 0 >>= fun () ->
+
+    (* Test JSON functions if supported (optional) *)
+    (try
+      M.prepare dbh "SELECT JSON_TYPE(data) FROM ocaml_mariadb_json_test LIMIT 1"
+        >>= or_die "prepare json type"
+        >>= fun json_func_stmt ->
+      M.Stmt.execute json_func_stmt [||] >>= or_die "execute json type" >>= fun res ->
+      M.Res.fetch (module M.Row.Array) res >>= or_die "fetch json type" >>= function
+      | Some row ->
+          let json_type = match M.Field.value row.(0) with
+            | `Json j -> j
+            | `String s -> s
+            | _ -> failwith "Expected JSON or String from JSON_TYPE"
+          in
+          (* JSON_TYPE should return something like "OBJECT", "ARRAY", etc. *)
+          assert (String.length json_type > 0);
+          M.Stmt.close json_func_stmt >>= or_die "close json func stmt"
+      | None -> return ()
+    with
+    | _ -> return () (* JSON functions might not be supported in all versions *)
+    ) >>= fun () ->
+
+    M.Stmt.close select_stmt >>= or_die "close select stmt" >>= fun () ->
+    M.Stmt.close insert_stmt >>= or_die "close insert stmt" >>= fun () ->
+    M.close dbh
+
   let main () =
     test_server_properties () >>= fun () ->
     test_insert_id () >>= fun () ->
     test_txn () >>= fun () ->
+    test_json () >>= fun () ->
     test_many_select () >>= fun () ->
     test_integer () >>= fun () -> test_bigint ()
 end