无法使用PG'；连接PostgreSQL数据库；奥卡姆

我最近尝试使用OCaml处理Postgres数据库。我找到了PG'Ocaml库，并研究了第一个示例。这就是错误：

$ make
ocamlfind ocamlc -package pgocaml,pgocaml.syntax -syntax camlp4o -c test.ml
File "test.ml", line 7, characters 23-146 (end at line 12, character 2):
Camlp4: Uncaught exception: Unix.Unix_error (20 | CstTag21, "connect", "")

File "test.ml", line 1:
Error: Preprocessor error
make: *** [test.cmo] Error 2

这里有一个类似的问题（），但结论对我来说并不适用，因为日志记录使用

$ psql -h localhost -d adam - U adam

完全有效，我已经包括了线

let dbh = PGOCaml.connect ~host:"localhost" ~user:"adam" ~datebase:"adam"
  ~password:"******" () in

输入我的代码

这是我的Makefile：

PROJECT := test
LINK_PKG := pgocaml
COMP_PKG := pgocaml,pgocaml.syntax

all: $(PROJECT)

$(PROJECT): $(PROJECT).cmo
    ocamlfind ocamlc -package $(LINK_PKG) -linkpkg -o $@ $<

$(PROJECT).cmo: $(PROJECT).ml
    ocamlfind ocamlc -package $(COMP_PKG) -syntax camlp4o -c $<

---

错误来自camlp4和第7行，第一行使用PG'OCaml的语法扩展。因此，这可能是一个解析问题，与连接到数据库无关。尝试简化您的示例。您是对的，语法PGSQL（dbh）“…”是实际问题。谢谢！

open Printf

let () =
  let dbh = PGOCaml.connect ~host:"localhost" ~user:"adam" ~datebase:"adam"
  ~password:"******" () in

  PGSQL(dbh) "execute" "create temporary table employees (
id serial not null primary key,
name text not null,
salary int4 not null,
email text
)";

  let insert =
    PGPREPARE(dbh) "opt-args"
    "insert into employees (name, salary, email)
values ($name, $salary, $?email)"
  in
  insert "Ann" 10_000_l ();
  insert "Bob" 45_000_l ();
  insert "Jim" 20_000_l ();
  insert ~name:"Mary" ~salary:30_000_l ~email:"mary@example.com" ();

  let rows = PGSQL(dbh) "select id, name, salary, email from employees" in
  List.iter (
    fun (id, name, salary, email) ->
      let email = match email with Some email -> email | None -> "-" in
      printf "%ld %S %ld %S\n" id name salary email
  ) rows;

  let ids = [ 1_l; 3_l ] in
  let rows = PGSQL(dbh) "select id, name, salary, email from employees
where id in $@ids" in
  List.iter (
    fun (id, name, salary, email) ->
      let email = match email with Some email -> email | None -> "-" in
      printf "%ld %S %ld %S\n" id name salary email
  ) rows;

  PGOCaml.close dbh