CP-307947: [maintenance]: add .mli files to all database modules (#6460)

ocaml-lsp-server's 'Action->Infer interface' was used for this, and then
removed internal/unused entries.

Having an mli file is useful:
* can find dead code more easily if it is clear which functions are
internal to a module and which aren't
* the impact of refactoring changes is more obvious (did we have to
change an mli at all?)
* makes it easier to understand what a module does

There are some .ml files which only contain types, these are instead
renamed to .mli and dune's `modules_without_implementation` feature is
used.
Executables get an empty .mli (recent versions of dune already do the
equivalent of this, but this makes it more obvious).

Drop code from .ml files that now show up as unused.

Eventually we can also add some documentation, this will be done in
followup PRs for new code.

Author: edwintorok

ocaml/database/block_device_io.mli

@@ -0,0 +1 @@
+(* this file is empty on purpose: this is an executable file *)

ocaml/database/block_device_io_errors.mli

@@ -0,0 +1,19 @@
+(*
+ * Copyright (C) Cloud Software Group
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published
+ * by the Free Software Foundation; version 2.1 only. with the special
+ * exception on linking described in file LICENSE.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Lesser General Public License for more details.
+ *)
+
+val timeout_error_msg : string
+
+val not_enough_space_error_msg : string
+
+val not_initialised_error_msg : string

ocaml/database/database_server_main.mli

@@ -0,0 +1 @@
+(* this file is empty on purpose: this is an executable file *)

ocaml/database/db_action_helper.ml

@@ -20,16 +20,5 @@ let __callback :
 
 let events_register f = __callback := Some f
 
-let events_unregister () = __callback := None
-
 let events_notify ?snapshot ty op ref =
   match !__callback with None -> () | Some f -> f ?snapshot ty op ref
-
-(*
-exception Db_set_or_map_parse_fail of string
-
-let parse_sexpr s : SExpr.t list =
-  match SExpr_TS.of_string s with
-    | SExpr.Node xs -> xs
-    | _ -> raise (Db_set_or_map_parse_fail s)
-*)

ocaml/database/db_action_helper.mli

@@ -0,0 +1,18 @@
+(*
+ * Copyright (C) Cloud Software Group
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published
+ * by the Free Software Foundation; version 2.1 only. with the special
+ * exception on linking described in file LICENSE.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Lesser General Public License for more details.
+ *)
+
+val events_register :
+  (?snapshot:Rpc.t -> string -> string -> string -> unit) -> unit
+
+val events_notify : ?snapshot:Rpc.t -> string -> string -> string -> unit

ocaml/database/db_cache.mli

@@ -0,0 +1,17 @@
+(*
+ * Copyright (C) Cloud Software Group
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published
+ * by the Free Software Foundation; version 2.1 only. with the special
+ * exception on linking described in file LICENSE.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Lesser General Public License for more details.
+ *)
+
+val get : Db_ref.t -> (module Db_interface.DB_ACCESS)
+
+val apply_delta_to_cache : Redo_log.t -> Db_ref.t -> unit

ocaml/database/db_cache_test.mli

@@ -0,0 +1 @@
+(* this file is empty on purpose: this is an executable file *)

ocaml/database/db_connections.mli

@@ -0,0 +1,29 @@
+(*
+ * Copyright (C) Cloud Software Group
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published
+ * by the Free Software Foundation; version 2.1 only. with the special
+ * exception on linking described in file LICENSE.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Lesser General Public License for more details.
+ *)
+
+val get_dbs_and_gen_counts : unit -> (int64 * Parse_db_conf.db_connection) list
+
+val choose :
+  Parse_db_conf.db_connection list -> Parse_db_conf.db_connection option
+
+val preferred_write_db : unit -> Parse_db_conf.db_connection
+
+val exit_on_next_flush : bool ref
+
+val inc_db_flush_thread_refcount : unit -> unit
+
+val flush_dirty_and_maybe_exit :
+  Parse_db_conf.db_connection -> int option -> bool
+
+val flush : Parse_db_conf.db_connection -> Db_cache_types.Database.t -> unit

ocaml/database/db_exn.mli

@@ -0,0 +1,39 @@
+(*
+ * Copyright (C) Cloud Software Group
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published
+ * by the Free Software Foundation; version 2.1 only. with the special
+ * exception on linking described in file LICENSE.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Lesser General Public License for more details.
+ *)
+
+(** class * field * uuid * key *)
+exception Duplicate_key of string * string * string * string
+
+(** message * class * key *)
+exception DBCache_NotFound of string * string * string
+
+(** class * field * key *)
+exception Uniqueness_constraint_violation of string * string * string
+
+(** class * field * value *)
+exception Integrity_violation of string * string * string
+
+(** class * _ * uuid *)
+exception Read_missing_uuid of string * string * string
+
+(** class * _ * uuid *)
+exception Too_many_values of string * string * string
+
+exception Remote_db_server_returned_unknown_exception
+
+exception Remote_db_server_returned_bad_message
+
+exception Empty_key_in_map
+
+exception Invalid_value

ocaml/database/db_filter.ml

@@ -18,33 +18,6 @@
 
 open Db_filter_types
 
-let string_of_val = function
-  | Field x ->
-      "Field " ^ x
-  | Literal x ->
-      "Literal " ^ x
-
-let rec string_of_expr =
-  let binexpr name a b =
-    Printf.sprintf "%s (%s, %s)" name (string_of_expr a) (string_of_expr b)
-  in
-  let binval name a b =
-    Printf.sprintf "%s (%s, %s)" name (string_of_val a) (string_of_val b)
-  in
-  function
-  | True ->
-      "True"
-  | False ->
-      "False"
-  | Not x ->
-      Printf.sprintf "Not ( %s )" (string_of_expr x)
-  | And (a, b) ->
-      binexpr "And" a b
-  | Or (a, b) ->
-      binexpr "Or" a b
-  | Eq (a, b) ->
-      binval "Eq" a b
-
 exception XML_unmarshall_error
 
 let val_of_xml xml =