{"result":{"depiction_url":null,"edges":{"relation":{"objects":[{"created":"2026-10-07T11:13:33Z","object_id":{"id":2955,"is_a":["text","documentation","developerguide"],"name":"developer_datamodel_fixtures","title":{"_type":"trans","tr":{"en":"Install initial content with a datamodel"}},"uri":"https:\/\/zotonic.com\/id\/2955"},"seq":1},{"created":"2026-10-07T11:13:33Z","object_id":{"id":2956,"is_a":["text","documentation","developerguide"],"name":"developer_database_queries","title":{"_type":"trans","tr":{"en":"Add a database query when models are not enough"}},"uri":"https:\/\/zotonic.com\/id\/2956"},"seq":2},{"created":"2026-10-07T11:13:33Z","object_id":{"id":2994,"is_a":["text","documentation","developerguide"],"name":"developer_deployment_workflow","title":{"_type":"trans","tr":{"en":"Deploy a repeatable release"}},"uri":"https:\/\/zotonic.com\/id\/2994"},"seq":3}],"predicate":{"id":303,"is_a":["meta","predicate"],"name":"relation","title":{"_type":"trans","tr":{"nl":"Relatie","en":"Relation"}},"uri":"http:\/\/purl.org\/dc\/terms\/relation"}},"subject":{"objects":[{"created":"2026-10-07T11:13:33Z","object_id":{"id":2554,"is_a":["categorization","keyword","keyword_information_type"],"name":"zotonic_topic_how_to_guide","title":"How-to guide","uri":"https:\/\/zotonic.com\/id\/2554"},"seq":1},{"created":"2026-10-07T11:13:33Z","object_id":{"id":2564,"is_a":["categorization","keyword","keyword_audience"],"name":"zotonic_topic_backend_developer","title":"Backend developer","uri":"https:\/\/zotonic.com\/id\/2564"},"seq":2},{"created":"2026-10-07T11:13:33Z","object_id":{"id":2631,"is_a":["categorization","keyword","keyword_architecture"],"name":"zotonic_topic_database","title":"Database","uri":"https:\/\/zotonic.com\/id\/2631"},"seq":3},{"created":"2026-10-07T11:13:33Z","object_id":{"id":2658,"is_a":["categorization","keyword","keyword_task"],"name":"zotonic_topic_migrate","title":"Migrate","uri":"https:\/\/zotonic.com\/id\/2658"},"seq":4},{"created":"2026-10-07T11:13:33Z","object_id":{"id":2635,"is_a":["categorization","keyword","keyword_architecture"],"name":"zotonic_topic_module","title":"Module","uri":"https:\/\/zotonic.com\/id\/2635"},"seq":5}],"predicate":{"id":308,"is_a":["meta","predicate"],"name":"subject","title":{"_type":"trans","tr":{"en":"Keyword"}},"uri":"http:\/\/purl.org\/dc\/elements\/1.1\/subject"}}},"id":2962,"is_a":["text","documentation","developerguide"],"links":[{"rel":"self","target":"https:\/\/zotonic.com\/.zotonic\/websub\/topic\/2962"},{"rel":"hub","target":"https:\/\/zotonic.com\/.zotonic\/websub"}],"medium":null,"medium_url":null,"name":"developer_schema_upgrades","page_url":{"en":"https:\/\/zotonic.com\/docs\/2962\/upgrade-a-module-s-data-schema","x-default":"https:\/\/zotonic.com\/docs\/2962\/upgrade-a-module-s-data-schema"},"preview_url":null,"resource":{"body":{"_type":"trans","tr":{"en":"<p>Version schema changes through the module&#39;s installation and upgrade mechanism. Inspect a module using <code>-mod_schema<\/code> and <code>manage_schema\/2<\/code> before adding your own versioned step.<\/p>\n<p>Make each step safe for the state it may encounter after a partial attempt. Separate database structure changes from long-running data conversion when a single startup transaction would be too costly.<\/p>\n<p>Test a fresh install and an upgrade from the previously released schema. Keep a database backup for the upgrade test and verify application behavior after migration, not just the table definitions.<\/p>\n<p>If version 1 installed the Garden fixture, change the declaration to <code>-mod_schema(2).<\/code> for the next release. Keep the fresh-install clause and add a <code>manage_schema({upgrade, 2}, Context)<\/code> clause for the version-1-to-2 change. Erlang function clauses are separated with semicolons. Do not return success for an upgrade you have not implemented.<\/p>\n<p>The manager calls upgrades in sequence, within a database transaction per schema step, then applies any returned datamodel and records the version. A code reload alone is not an upgrade test: run the module activation\/startup lifecycle on the test site. Use <code>manage_data\/2<\/code> for a deliberate follow-up after schema work, or queue longer conversions. Compare fresh-install and upgraded data before release.<\/p>"}},"category_id":{"id":317,"is_a":["meta","category"],"name":"developerguide","title":"Developer guide","uri":"https:\/\/zotonic.com\/id\/developerguide"},"content_group_id":{"id":339,"is_a":["meta","content_group"],"name":"default_content_group","title":{"_type":"trans","tr":{"en":"Default Content Group"}},"uri":"https:\/\/zotonic.com\/id\/default_content_group"},"created":"2026-10-07T11:12:56Z","creator_id":{"id":1,"is_a":["person"],"name":"administrator","title":"Site Administrator","uri":"https:\/\/zotonic.com\/id\/1"},"doc_editorial_bundle":true,"doc_editorial_edges":{"relation":[2955,2956,2994],"subject":[2554,2564,2631,2635,2658]},"is_authoritative":true,"is_dependent":false,"is_featured":false,"is_protected":false,"is_published":true,"is_unfindable":false,"language":["en"],"modified":"2026-10-07T11:13:41Z","modifier_id":{"id":1,"is_a":["person"],"name":"administrator","title":"Site Administrator","uri":"https:\/\/zotonic.com\/id\/1"},"name":"developer_schema_upgrades","pivot_geocode":null,"pivot_location_lat":null,"pivot_location_lng":null,"privacy":0,"publication_end":"9999-06-01T00:00:00Z","publication_start":"2026-10-07T11:12:56Z","slug":"upgrade-a-module-s-data-schema","summary":{"_type":"trans","tr":{"en":"Version schema changes through the module&#39;s installation and upgrade mechanism. Inspect a module using -mod_schema and manage_schema\/2 before adding your own versioned step."}},"title":{"_type":"trans","tr":{"en":"Upgrade a module&#39;s data schema"}},"title_slug":{"_type":"trans","tr":{"en":"upgrade-a-module-s-data-schema"}},"tz":"UTC","uri":null,"version":20,"visible_for":0},"uri":"https:\/\/zotonic.com\/id\/2962","uri_template":"https:\/\/zotonic.com\/id\/:id","websub":{"hub":"https:\/\/zotonic.com\/.zotonic\/websub","topic":"https:\/\/zotonic.com\/.zotonic\/websub\/topic\/2962"}},"status":"ok"}