{"id":5192,"date":"2015-08-25T14:17:29","date_gmt":"2015-08-25T12:17:29","guid":{"rendered":"https:\/\/www.dbi-services.com\/blog\/representing-ranges-with-one-data-type\/"},"modified":"2015-08-25T14:17:29","modified_gmt":"2015-08-25T12:17:29","slug":"representing-ranges-with-one-data-type","status":"publish","type":"post","link":"https:\/\/www.dbi-services.com\/blog\/representing-ranges-with-one-data-type\/","title":{"rendered":"Representing ranges with one data type?"},"content":{"rendered":"<p>How many applications do you know that need to define a validity of a row? And how many of these do that by adding two columns: valid_from and valid_to or similar column names? Well, in PostgreSQL (you already suspect it \ud83d\ude42 ) there is much more elegant way to do that. PostgreSQL knows the concept of <a href=\"http:\/\/www.postgresql.org\/docs\/current\/static\/rangetypes.html\" target=\"_blank\" rel=\"noopener\">range types<\/a>. Several of these are pre-defined and you get them once you install PostgreSQL:<\/p>\n<ul>\n<li>int4range \u2014 Range of integer<\/li>\n<li>int8range \u2014 Range of bigint<\/li>\n<li>numrange \u2014 Range of numeric<\/li>\n<li>tsrange \u2014 Range of timestamp without time zone<\/li>\n<li>tstzrange \u2014 Range of timestamp with time zone<\/li>\n<li>daterange \u2014 Range of date<\/li>\n<\/ul>\n<p>The classical example for using range types is a booking system for meeting rooms. Meeting rooms are booked for a period of time and the booking system has to know which periods are free before presenting possible choices. Lets do a simple test setup:<\/p>\n<pre class=\"brush: sql; gutter: true; first-line: 1\">\ncreate extension if not exists btree_gist;\ndrop table if exists meeting_rooms_booked;\ndrop table if exists meeting_rooms;\ncreate table meeting_rooms ( id int primary key\n                           , mname varchar(20)\n                           , location varchar(10)\n                           );\ncreate table meeting_rooms_booked ( mid int references meeting_rooms(id)\n                                  , booking_range tsrange\n                                  , exclude using gist (mid with =,booking_range with &amp;&amp;)\n                                  );\ninsert into meeting_rooms ( id, mname, location)\n       values ( 1, 'meetingsouth', 'south' )\n            , ( 2, 'meetingnorth', 'north' )\n            , ( 3, 'meetingwest', 'west' )\n            , ( 4, 'meetingeast', 'east' );\ninsert into meeting_rooms_booked ( mid, booking_range )\n       values ( 1, '[2015-01-01 15:00, 2015-01-01 18:30]' )\n            , ( 1, '[2015-01-01 08:00, 2015-01-01 08:30]' )\n            , ( 2, '[2015-03-01 17:00, 2015-03-01 18:30]' )\n            , ( 1, '[2015-03-01 05:00, 2015-03-01 08:30]' )\n            , ( 3, '[2015-02-01 15:00, 2015-02-01 18:30]' )\n            , ( 4, '[2015-02-01 19:00, 2015-02-01 20:30]' )\n            , ( 4, '[2015-03-01 15:00, 2015-03-01 18:30]' );\n<\/pre>\n<p>Lets say we want to know if meeting room number 3 is free at the 1st of February 2015 between 16:00 and 16:30. Using the <a href=\"http:\/\/www.postgresql.org\/docs\/current\/static\/functions-range.html#RANGE-OPERATORS-TABLE\" target=\"_blank\" rel=\"noopener\">range type operator<\/a> &#8220;&amp;&amp;&#8221; (overlap) this is easy to ask:<\/p>\n<pre class=\"brush: sql; gutter: true; first-line: 1\">\npostgres=# select * from meeting_rooms_booked where mid = 3;\n mid |                 booking_range                 \n-----+-----------------------------------------------\n   3 | [\"2015-02-01 15:00:00\",\"2015-02-01 18:30:00\"]\n(1 row)\n\npostgres=# select booking_range &amp;&amp; '[2015-02-01 16:00,2015-02-01 16:30)'::tsrange from meeting_rooms_booked where mid = 3;\n ?column? \n----------\n t\n(1 row)\n<\/pre>\n<p>Indeed this does overlap. If we ask for a period for which the room is free we get false:<\/p>\n<pre class=\"brush: sql; gutter: true; first-line: 1\">\npostgres=# select booking_range &amp;&amp; '[2015-02-01 18:45,2015-02-01 19:15)'::tsrange from meeting_rooms_booked where mid = 3;\n ?column? \n----------\n f\n(1 row)\n<\/pre>\n<p>If you go back to the table definition of meeting_rooms_booked the &#8220;&amp;&amp;&#8221; operator is used to enforce that there can not be two bookings which overlap in time. This is the reason the btree_gist extension was installed as normal btree indexes can not be created on range type columns.<\/p>\n<p>So, if it is about a booking system or simple valid_from\/valid_to definitions or something else which will benefit from this goody: range types are what you need \ud83d\ude42<\/p>\n","protected":false},"excerpt":{"rendered":"<p>How many applications do you know that need to define a validity of a row? And how many of these do that by adding two columns: valid_from and valid_to or similar column names? Well, in PostgreSQL (you already suspect it \ud83d\ude42 ) there is much more elegant way to do that. PostgreSQL knows the concept [&hellip;]<\/p>\n","protected":false},"author":29,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[229],"tags":[77],"type_dbi":[],"class_list":["post-5192","post","type-post","status-publish","format-standard","hentry","category-database-administration-monitoring","tag-postgresql"],"acf":[],"yoast_head":"<!-- This site is optimized with the Yoast SEO Premium plugin v27.2 (Yoast SEO v27.2) - https:\/\/yoast.com\/product\/yoast-seo-premium-wordpress\/ -->\n<title>Representing ranges with one data type? - dbi Blog<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/www.dbi-services.com\/blog\/representing-ranges-with-one-data-type\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Representing ranges with one data type?\" \/>\n<meta property=\"og:description\" content=\"How many applications do you know that need to define a validity of a row? And how many of these do that by adding two columns: valid_from and valid_to or similar column names? Well, in PostgreSQL (you already suspect it \ud83d\ude42 ) there is much more elegant way to do that. 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He has more than 15 years of experience in management, engineering and optimization of databases and infrastructures, especially on Oracle and PostgreSQL. Since the beginning of his career, he has specialized in Oracle Technologies and is Oracle Certified Professional 12c and Oracle Certified Expert RAC\/GridInfra. Over time, Daniel has become increasingly interested in open source technologies, becoming \u201cTechnology Leader Open Infrastructure\u201d and PostgreSQL expert. \u00a0Based on community or EnterpriseDB tools, he develops and installs complex high available solutions with PostgreSQL. He is also a certified PostgreSQL Plus 9.0 Professional and a Postgres Advanced Server 9.4 Professional. He is a regular speaker at PostgreSQL conferences in Switzerland and Europe. Today Daniel is also supporting our customers on AWS services such as AWS RDS, database migrations into the cloud, EC2 and automated infrastructure management with AWS SSM (System Manager). 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He has more than 15 years of experience in management, engineering and optimization of databases and infrastructures, especially on Oracle and PostgreSQL. Since the beginning of his career, he has specialized in Oracle Technologies and is Oracle Certified Professional 12c and Oracle Certified Expert RAC\/GridInfra. Over time, Daniel has become increasingly interested in open source technologies, becoming \u201cTechnology Leader Open Infrastructure\u201d and PostgreSQL expert. \u00a0Based on community or EnterpriseDB tools, he develops and installs complex high available solutions with PostgreSQL. He is also a certified PostgreSQL Plus 9.0 Professional and a Postgres Advanced Server 9.4 Professional. He is a regular speaker at PostgreSQL conferences in Switzerland and Europe. Today Daniel is also supporting our customers on AWS services such as AWS RDS, database migrations into the cloud, EC2 and automated infrastructure management with AWS SSM (System Manager). He is a certified AWS Solutions Architect Professional. Prior to dbi services, Daniel was Management System Engineer at LC SYSTEMS-Engineering AG in Basel. Before that, he worked as Oracle Developper &amp;\u00a0Project Manager at Delta Energy Solutions AG in Basel (today Powel AG). Daniel holds a diploma in Business Informatics (DHBW, Germany). 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