CP-49140: [prep] database: use separate types, not string everywhere

Currently all of these are strings, but it may change:
* table
* db_ref
* field_name
* field
* uuid

This enables changing the `field` type from `string`
and avoiding costly serialization/deserialization when not needed.

No functional change.

Signed-off-by: Edwin Török <edwin.torok@cloud.com>

Author: edwintorok

ocaml/database/db_cache_impl.ml

@@ -271,7 +271,7 @@ let read_refs t tblname =
   Table.fold (fun r _ _ acc -> r :: acc) tbl []
 
 (* Return a list of all the refs for which the expression returns true. *)
-let find_refs_with_filter_internal db (tblname : string)
+let find_refs_with_filter_internal db (tblname : Db_interface.table)
     (expr : Db_filter_types.expr) =
   let tbl = TableSet.find tblname (Database.tableset db) in
   let eval_val row = function

ocaml/database/db_interface.ml

@@ -23,79 +23,92 @@ module type RPC = sig
   (** [rpc request] transmits [request] and receives a response *)
 end
 
+type table = string
+
+type field_name = string
+
+type field = string
+
+type db_ref = string
+
+type uuid = string
+
+type regular_fields = (field_name * field) list
+
+type associated_fields = (field_name * db_ref list) list
+
 (** dictionary of regular fields x dictionary of associated set_ref values *)
-type db_record = (string * string) list * (string * string list) list
+type db_record = regular_fields * associated_fields
 
 (** The client interface to the database *)
 module type DB_ACCESS = sig
   val initialise : unit -> unit
   (** [initialise ()] must be called before any other function in this
       		interface *)
 
-  val get_table_from_ref : Db_ref.t -> string -> string option
-  (** [get_table_from_ref ref] returns [Some tbl] if [ref] is a
+  val get_table_from_ref : Db_ref.t -> db_ref -> table option
+  (** [get_table_from_ref ref tbl] returns [Some tbl] if [ref] is a
       		valid reference; None otherwise *)
 
-  val is_valid_ref : Db_ref.t -> string -> bool
+  val is_valid_ref : Db_ref.t -> db_ref -> bool
   (** [is_valid_ref ref] returns true if [ref] is valid; false otherwise *)
 
-  val read_refs : Db_ref.t -> string -> string list
+  val read_refs : Db_ref.t -> table -> db_ref list
   (** [read_refs tbl] returns a list of all references in table [tbl] *)
 
   val find_refs_with_filter :
-    Db_ref.t -> string -> Db_filter_types.expr -> string list
+    Db_ref.t -> table -> Db_filter_types.expr -> db_ref list
   (** [find_refs_with_filter tbl expr] returns a list of all references
       		to rows which match [expr] *)
 
-  val read_field_where : Db_ref.t -> Db_cache_types.where_record -> string list
+  val read_field_where : Db_ref.t -> Db_cache_types.where_record -> field list
   (** [read_field_where {tbl,return,where_field,where_value}] returns a
       		list of the [return] fields in table [tbl] where the [where_field]
       		equals [where_value] *)
 
-  val db_get_by_uuid : Db_ref.t -> string -> string -> string
+  val db_get_by_uuid : Db_ref.t -> table -> uuid -> db_ref
   (** [db_get_by_uuid tbl uuid] returns the single object reference
       		associated with [uuid] *)
 
-  val db_get_by_uuid_opt : Db_ref.t -> string -> string -> string option
+  val db_get_by_uuid_opt : Db_ref.t -> table -> uuid -> db_ref option
   (** [db_get_by_uuid_opt tbl uuid] returns [Some obj] with the single object
           reference associated with [uuid] if one exists and [None] otherwise,
           instead of raising an exception like [get_by_uuid] *)
 
-  val db_get_by_name_label : Db_ref.t -> string -> string -> string list
+  val db_get_by_name_label : Db_ref.t -> table -> string -> db_ref list
   (** [db_get_by_name_label tbl label] returns the list of object references
       		associated with [label] *)
 
-  val create_row :
-    Db_ref.t -> string -> (string * string) list -> string -> unit
+  val create_row : Db_ref.t -> table -> regular_fields -> db_ref -> unit
   (** [create_row tbl kvpairs ref] create a new row in [tbl] with
       		key [ref] and contents [kvpairs] *)
 
-  val delete_row : Db_ref.t -> string -> string -> unit
+  val delete_row : Db_ref.t -> db_ref -> table -> unit
   (** [delete_row context tbl ref] deletes row [ref] from table [tbl] *)
 
-  val write_field : Db_ref.t -> string -> string -> string -> string -> unit
+  val write_field : Db_ref.t -> table -> db_ref -> field_name -> field -> unit
   (** [write_field context tbl ref fld val] changes field [fld] to [val] in
       		row [ref] in table [tbl] *)
 
-  val read_field : Db_ref.t -> string -> string -> string -> string
-  (** [read_field context tbl ref fld] returns the value of field [fld]
+  val read_field : Db_ref.t -> table -> field_name -> db_ref -> field
+  (** [read_field context tbl fld ref] returns the value of field [fld]
       		in row [ref] in table [tbl] *)
 
-  val read_record : Db_ref.t -> string -> string -> db_record
+  val read_record : Db_ref.t -> table -> db_ref -> db_record
   (** [read_record tbl ref] returns
       		[ (field, value) ] * [ (set_ref fieldname * [ ref ]) ] *)
 
   val read_records_where :
-    Db_ref.t -> string -> Db_filter_types.expr -> (string * db_record) list
+    Db_ref.t -> table -> Db_filter_types.expr -> (db_ref * db_record) list
   (** [read_records_where tbl expr] returns a list of the values returned
       		by read_record that match the expression *)
 
   val process_structured_field :
        Db_ref.t
-    -> string * string
-    -> string
-    -> string
-    -> string
+    -> field_name * field
+    -> table
+    -> field_name
+    -> db_ref
     -> Db_cache_types.structured_op_t
     -> unit
   (** [process_structured_field context kv tbl fld ref op] modifies the

ocaml/tests/dune

@@ -65,6 +65,7 @@
   (modules suite_alcotest_server test_client test_valid_ref_list test_vm_group)
   (libraries
     alcotest
+    xapi_database
     httpsvr
     tests_common
     xapi-client

ocaml/xapi/dune

@@ -227,7 +227,7 @@
   (name xapi_internal_server_only)
   (modes best)
   (modules server)
-  (libraries xapi_internal_minimal http_lib rpclib.core xapi-types xapi-log xapi-stdext-encodings xapi-consts xapi-backtrace xapi-stdext-date rpclib.json)
+  (libraries xapi_database xapi_internal_minimal http_lib rpclib.core xapi-types xapi-log xapi-stdext-encodings xapi-consts xapi-backtrace xapi-stdext-date rpclib.json)
   (wrapped false)
 )