PostgreSQL的設置自定義約束

Question

我有一個約會的表這種結構（分塊的可讀性）：

appointments: 
- id 
- staff_id 
- start_time 
- end_time 
- cancelled 

我想添加一個數據庫約束不能夠翻一番預訂約會。我在想，如果有可能的線沿線的添加約束條件：

when staff_id = ? and cancelled = false then set a "unique" constraint on start_time

如果這是不可能有類似的東西我可以做實現我的最終目標？

編輯

這是全預約表

CREATE TABLE "appointments" (
      "id" uuid, 
      "customer_id" uuid NOT NULL REFERENCES customers ON DELETE CASCADE ON UPDATE CASCADE, 
      "staff_id" uuid NOT NULL REFERENCES staff ON DELETE CASCADE ON UPDATE CASCADE, 
      "start_time" timestamp NOT NULL, 
      "end_time" timestamp NOT NULL, 
      "notes" text, 
      "cancelled" boolean NOT NULL DEFAULT false, 
      "created_at" timestamp with time zone NOT NULL, 
      "updated_at" timestamp with time zone NOT NULL, 
     ); 

用排除法：

CREATE TABLE "appointments" (
     "id" uuid, 
     "customer_id" uuid NOT NULL REFERENCES customers ON DELETE CASCADE ON UPDATE CASCADE, 
     "staff_id" uuid NOT NULL REFERENCES staff ON DELETE CASCADE ON UPDATE CASCADE, 
     "start_time" timestamp NOT NULL, 
     "end_time" timestamp NOT NULL, 
     "notes" text, 
     "cancelled" boolean NOT NULL DEFAULT false, 
     "created_at" timestamp with time zone NOT NULL, 
     "updated_at" timestamp with time zone NOT NULL, 
     EXCLUDE USING gist (
      staff_id WITH =, 
      tsrange(start_time, end_time) WITH && 
     ) WHERE (NOT cancelled), 
     PRIMARY KEY ("id") 
    ); 

與排除錯誤執行：

data type uuid has no default operator class for access method "gist"

Answer 1

您需要排除約束來停止約會的雙重預約。所選答案中的方法只會停止兩個約會具有相同的開始時間。如果它在第一次約會之後開始，它不會阻止一個約會重疊。

CREATE TABLE appointments (
    id   serial PRIMARY KEY, 
    staff_id int, 
    start_time timestamp, 
    end_time timestamp, 
    cancelled bool DEFAULT false, 
    EXCLUDE USING gist (
    staff_id WITH =, 
    tsrange(start_time, end_time) WITH && 
) WHERE (NOT cancelled) 
); 

現在你不能預約預約。

INSERT INTO appointments (staff_id, start_time, end_time) VALUES 
    (1, '01-01-2010T07:30', '01-01-2010T09:30'), 
    (1, '01-01-2010T08:00', '01-01-2010T09:45') 
; 

ERROR: conflicting key value violates exclusion constraint "appointments_staff_id_tsrange_excl" 
DETAIL: Key (staff_id, tsrange(start_time, end_time))=(1, ["2010-01-01 08:00:00","2010-01-01 09:45:00")) conflicts with existing key (staff_id, tsrange(start_time, end_time))=(1, ["2010-01-01 07:30:00","2010-01-01 09:30:00")). 

您也可以刪除start_time和end_time，並把它們都作爲timestamp-ranges

Answer 2

create unique index the_index on appointments (staff_id, start_time) 
where not cancelled;