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feat: updated category delete trigger to recurse
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -1,89 +1,43 @@ | ||
| /* | ||
| This SQL script sets up a trigger and a supporting function to handle custom cascading | ||
| deletion behavior for categories in the `mto_category` table, per the application requirements. | ||
| Updated Assumption (per user's note): | ||
| ------------------------------------- | ||
| Instead of assigning milestones to a designated "Uncategorized" category with a known UUID, | ||
| we will set their `mto_category_id` to NULL (a "nil" UUID), indicating they are now uncategorized. | ||
| Requirements: | ||
| - Deleting a subcategory: | ||
| * All milestones referencing that subcategory should be reassigned to its parent category. | ||
| - Deleting a top-level category: | ||
| * All milestones referencing the deleted top-level category or its direct subcategories | ||
| should have `mto_category_id` set to NULL, indicating they are now uncategorized. | ||
| * All direct subcategories of the deleted category should be deleted. | ||
| Why the "CASCADE" Keyword Isn't Used: | ||
| ------------------------------------- | ||
| The standard ON DELETE CASCADE simply removes dependent rows. Here, we need to reassign | ||
| references rather than just delete them. Since this behavior is more complex, we implement | ||
| custom logic in a trigger and a PL/pgSQL function rather than relying on cascade deletes. | ||
| Usage: | ||
| - Once this script is applied, a `DELETE FROM mto_category WHERE id = 'some-category-uuid';` | ||
| will trigger the logic to reassign milestones and remove subcategories as defined. | ||
| Assumptions: | ||
| - When deleting a top-level category, milestones are "uncategorized" by setting their | ||
| `mto_category_id` to NULL. | ||
| - For subcategories, milestones are moved up to the parent category. | ||
| - This handles one level of subcategories. If a deeper hierarchy is required, | ||
| the logic should be extended to recursively handle all descendants. | ||
| */ | ||
|
|
||
| -- Drop existing trigger and function to allow clean re-creation | ||
| DROP TRIGGER IF EXISTS mto_category_before_delete ON mto_category; | ||
| DROP FUNCTION IF EXISTS rebalance_milestones_before_category_delete(); | ||
|
|
||
| -- Create the trigger function that implements the custom cascading logic | ||
| CREATE OR REPLACE FUNCTION rebalance_milestones_before_category_delete() | ||
| RETURNS TRIGGER AS $$ | ||
| DECLARE | ||
| cat_model_plan_id UUID; | ||
| is_top_level BOOLEAN; | ||
| cat_ids UUID[]; | ||
| BEGIN | ||
| -- Determine if the category is top-level or a subcategory | ||
| SELECT model_plan_id, (parent_id IS NULL) INTO cat_model_plan_id, is_top_level | ||
| FROM mto_category | ||
| WHERE id = OLD.id; | ||
|
|
||
| IF is_top_level THEN | ||
| -- TOP-LEVEL CATEGORY DELETION LOGIC: | ||
| -- Reassign all milestones referencing this category or its direct subcategories | ||
| -- to NULL, marking them as uncategorized. | ||
|
|
||
| UPDATE mto_milestone | ||
| SET mto_category_id = NULL | ||
| WHERE mto_category_id IN ( | ||
| SELECT id FROM mto_category | ||
| WHERE parent_id = OLD.id | ||
| UNION ALL | ||
| SELECT OLD.id | ||
| ); | ||
|
|
||
| -- Delete all direct subcategories of this category | ||
| DELETE FROM mto_category | ||
| WHERE parent_id = OLD.id; | ||
|
|
||
| -- The category itself (OLD.id) will be deleted by the original DELETE statement | ||
| ELSE | ||
| -- SUBCATEGORY DELETION LOGIC: | ||
| -- Move all milestones from this subcategory to its parent category | ||
| UPDATE mto_milestone | ||
| SET mto_category_id = OLD.parent_id | ||
| WHERE mto_category_id = OLD.id; | ||
|
|
||
| -- The subcategory (OLD.id) will be deleted by the original DELETE statement | ||
| IF pg_trigger_depth() > 1 THEN | ||
| RETURN OLD; | ||
| END IF; | ||
|
|
||
| RETURN OLD; -- Allow the DELETE to proceed after adjustments | ||
| -- Recursively gather all descendant categories, including OLD.id | ||
| WITH RECURSIVE cat_tree AS ( | ||
| SELECT id, parent_id | ||
| FROM mto_category | ||
| WHERE id = OLD.id | ||
| UNION ALL | ||
| SELECT c.id, c.parent_id | ||
| FROM mto_category c | ||
| JOIN cat_tree t ON t.id = c.parent_id | ||
| ) | ||
| SELECT array_agg(id) INTO cat_ids FROM cat_tree; | ||
|
|
||
| -- Always assign milestones to OLD.parent_id | ||
| -- If OLD.parent_id is NULL, they become uncategorized. | ||
| UPDATE mto_milestone | ||
| SET mto_category_id = OLD.parent_id | ||
| WHERE mto_category_id = ANY(cat_ids); | ||
|
|
||
| -- Delete all descendant categories except the current one | ||
| DELETE FROM mto_category | ||
| WHERE id != OLD.id | ||
| AND id = ANY(cat_ids); | ||
|
|
||
| RETURN OLD; | ||
| END; | ||
| $$ LANGUAGE plpgsql; | ||
|
|
||
| -- Create the trigger to invoke the above function before any category deletion | ||
| CREATE TRIGGER mto_category_before_delete | ||
| BEFORE DELETE ON mto_category | ||
| FOR EACH ROW | ||
| EXECUTE FUNCTION rebalance_milestones_before_category_delete(); | ||
| EXECUTE FUNCTION rebalance_milestones_before_category_delete(); |
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