postgreSQL-检查一个日期间隔是否与每行间隔数组中的日期间隔不重叠

Question

PostgreSQL(9.6), I am trying to check whether a date interval

('2018-11-18 12:00','2018-11-20 12:00')

does not overlap any of the following date intervals in the array

{('2018-11-21 12:00','2018-11-23 12:00'),('2018-11-19 12:00','2018-11-20 12:00')}

The elements in the array are composite:

CREATE TYPE reservation AS (
    checkIn TIMESTAMP WITHOUT TIME ZONE,
    checkOut TIMESTAMP WITHOUT TIME ZONE
)

Here is the rooms table:

CREATE TABLE rooms (
rId roomId PRIMARY KEY,
hRef hotelId NOT NULL,
rNo roomNo NOT NULL,
rType roomType,
numPeople INTEGER,
rBedOptions roomBed[],
reservations reservation[],
priceNight FLOAT,
FOREIGN KEY (hRef) REFERENCES hotels(hId) ON UPDATE CASCADE ON DELETE SET NULL  
)

INSERT INTO rooms VALUES
('R001','H001','101','one-bedroom',1,
ARRAY[row('1 twin')::roomBed],
ARRAY[
      row('2018-11-21 12:00','2018-11-23 12:00')::reservation,
      row('2018-11-19 12:00','2018-11-20 12:00')::reservation],
450.5);

Basically I am trying to check whether a "room" is available for a selected time interval by checking if this interval does not overlap with any existing reservation date intervals ('2018-11-21 12:00','2018-11-23 12:00'),('2018-11-19 12:00','2018-11-20 12:00'). So far I have been successful in checking the first element of the array for each row by writing the following query:

SELECT * FROM rooms R 
WHERE R.reservations[1] IS null 
OR NOT (('2018-11-18 12:00','2018-11-20 12:00') 
OVERLAPS (R.reservations[1].checkIn, R.reservations[1].checkOut)) 
ORDER BY rid;

The problem is that I don't know how to check all elements in the array if there is more than one. Any ideas or suggestions?

Answer 1

You can use unnest to transform array into row on the fly

SELECT * 
  FROM rooms R,
    LATERAL (SELECT bool_or(
                        ('2018-11-18 12:00','2018-11-20 12:00') 
                       OVERLAPS (periods.checkIn, periods.checkOut)
                   ) as someone_overlaps
              FROM unnest(R.reservations) periods
             ) ok
  WHERE someone_overlaps is not true
  ORDER BY rid;

Explain

1. For each row in this sentence you do a "Lateral" subselect to ask if it overlaps
2. Unnest array into several rows
3. Check the overlaps
4. Compute the OR of each overlap, take it in the someone_overlapas
5. List each row that not have someone_overlapas

Notes

• Booleans in postgress have three states: true , false and null thats why is not the same not someone_overlaps that someone_overlaps is not true , in the first case the null value remains null in the seconds null is not true . The second is used because the reservations may be an empty array.
• Lateral a keyword that allows to use previous tables (in the from list) to be used in the curren subselct
• unnest a function that transforms array into row
• you can see a living example at: https://dbfiddle.uk/?rdbms=postgres_10&fiddle=c070f0eeaf4206f0540d9187c5e874d3