How Can PostgreSQL's `tsrange` Type Optimize Queries for Business Hours?

Performing Hours of Operation Query in PostgreSQL

In PostgreSQL, you can perform a query to find all records that are "open" based on specified hours of operation using a combination of date and time comparisons. However, this approach can become complex, especially if the hours wrap around the end of the week.

Proposed Solution Using tsrange Type

To simplify and optimize this query, you can redesign the table to store opening hours as a set of tsrange (range of timestamp without time zone) values. This requires PostgreSQL version 9.2 or later and involves the following steps:

Table Layout:

• Create a table with a tsrange column named hours to store opening hours instead of separate columns for opening and closing times.

Example Data:

CREATE TABLE hoo (
  hoo_id  serial PRIMARY KEY
, shop_id int NOT NULL
, hours   tsrange NOT NULL
);

• Hours of operation for Wednesday 18:30 to Thursday 05:00 UTC can be inserted as:

INSERT INTO hoo(shop_id, hours)
VALUES (123, '[1996-01-03 18:30, 1996-01-04 05:00]');

Exclusion Constraint:

• An exclusion constraint is added to prevent overlapping entries per shop using the GiST index.

Helper Functions:

• Two helper functions, f_hoo_time() and f_hoo_hours(), are defined to normalize timestamps and split ranges crossing Sunday midnight.

Optimized Query:

Using the new table structure and helper functions, you can simplify your query to:

SELECT *
FROM hoo
WHERE hours @> f_hoo_time(now());

Benefits:

• The use of tsrange simplifies the query syntax and improves performance by leveraging a supported index.
• The exclusion constraint ensures data integrity and prevents overlapping entries.
• The GiST index provides fast and efficient search based on the hours field.
• The SP-GiST index on just hours further improves performance for queries involving large numbers of results.

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