From fc4b0e882e41de931c1398b877d209865511508f Mon Sep 17 00:00:00 2001
From: pashko <pm@pm.org.ru>
Date: Sun, 16 Feb 2025 19:37:39 +0800
Subject: [PATCH] Add how_to_update_views.md

---
 how_to_update_views.md | 81 ++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 81 insertions(+)
 create mode 100644 how_to_update_views.md

diff --git a/how_to_update_views.md b/how_to_update_views.md
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+### 1. Определить зависимости представления
+
+```sql
+WITH RECURSIVE view_dependencies AS (
+    -- Начинаем с document_details
+    SELECT 
+        c.oid AS view_oid,
+        c.relname AS view_name,
+        n.nspname AS schema_name,
+        NULL::text COLLATE "C" AS depends_on -- явная коллация
+    FROM pg_class c
+    JOIN pg_namespace n ON c.relnamespace = n.oid
+    WHERE c.relkind = 'v' -- Только представления
+        AND c.relname = 'document_details'
+
+    UNION ALL
+
+    -- Находим представления, зависящие от текущего списка
+    SELECT 
+        v.oid AS view_oid,
+        v.relname AS view_name,
+        n.nspname AS schema_name,
+        d.view_name COLLATE "C" AS depends_on -- явная коллация
+    FROM pg_class v
+    JOIN pg_namespace n ON v.relnamespace = n.oid
+    JOIN pg_views pv ON pv.schemaname = n.nspname AND pv.viewname = v.relname
+    JOIN view_dependencies d ON pv.definition ILIKE '%' || d.view_name || '%'
+    WHERE v.relkind = 'v' -- Только представления
+)
+SELECT * FROM view_dependencies;
+```
+
+### 2.Сохранить текущие скрипты создания представлений
+
+```sql
+SELECT format('CREATE OR REPLACE VIEW %I.%I AS %s;', 
+              n.nspname, c.relname, pg_get_viewdef(c.oid, true)) AS create_script
+FROM pg_class c
+JOIN pg_namespace n ON c.relnamespace = n.oid
+WHERE c.relkind = 'v' 
+    AND n.nspname = 'public'
+    AND c.relname IN ('document_details', 'author_documents');
+
+```
+
+
+### 3. Получить корректный порядок удаления
+
+```sql
+WITH RECURSIVE dependencies AS (
+    SELECT 
+        c.oid,
+        c.relname AS object_name,
+        n.nspname AS schema_name,
+        'VIEW' AS object_type,
+        NULL::text AS depends_on
+    FROM pg_class c
+    JOIN pg_namespace n ON c.relnamespace = n.oid
+    WHERE c.relkind = 'v' 
+        AND c.relname = 'document_details'
+
+    UNION ALL
+
+    SELECT 
+        d.refobjid AS oid,
+        c.relname AS object_name,
+        n.nspname AS schema_name,
+        'VIEW' AS object_type,
+        d.objid::regclass::text AS depends_on
+    FROM pg_depend d
+    JOIN pg_class c ON d.refobjid = c.oid
+    JOIN pg_namespace n ON c.relnamespace = n.oid
+    WHERE d.classid = 'pg_class'::regclass
+        AND d.refclassid = 'pg_class'::regclass
+        AND c.relkind = 'v'
+)
+SELECT format('DROP VIEW IF EXISTS %I.%I CASCADE;', schema_name, object_name) AS drop_script
+FROM dependencies
+ORDER BY object_type DESC;
+
+```