Implements automatic folder size update with trigger and function

database/migrations/20230820013540_update_folder_size.sql

@@ -0,0 +1,60 @@
+-- +goose Up
+-- +goose StatementBegin
+CREATE OR REPLACE FUNCTION teldrive.update_size_function()
+RETURNS TRIGGER AS $$
+DECLARE
+    rec RECORD;
+    total_size BIGINT;
+    batch_size INT := 100;
+    lower_bound INT := 0;
+    upper_bound INT := batch_size;
+BEGIN
+    LOOP
+        FOR rec IN
+            SELECT id, size
+            FROM teldrive.files
+            WHERE type = 'folder'
+            ORDER BY depth DESC
+            OFFSET lower_bound
+            LIMIT batch_size
+        LOOP
+            SELECT COALESCE(SUM(size),0) INTO total_size
+            FROM teldrive.files
+            WHERE parent_id = rec.id
+            AND status != 'pending_deletion';
+            
+            IF total_size <> rec.size THEN
+                UPDATE teldrive.files
+                SET size = total_size
+                WHERE id = rec.id;
+            END IF;
+
+            EXIT WHEN NOT FOUND;
+        END LOOP;
+
+        lower_bound := upper_bound;
+        upper_bound := upper_bound + batch_size;
+
+        EXIT WHEN NOT FOUND;
+    END LOOP;
+    RETURN NEW;
+END;
+$$ LANGUAGE plpgsql;
+-- +goose StatementEnd
+
+-- +goose StatementBegin
+CREATE TRIGGER update_folder_size_after_insert_or_update
+AFTER INSERT OR UPDATE OR DELETE ON teldrive.files
+FOR EACH ROW
+EXECUTE PROCEDURE teldrive.update_size_function();
+-- +goose StatementEnd
+
+
+-- +goose Down
+-- +goose StatementBegin
+
+DROP TRIGGER IF EXISTS update_folder_size_after_insert_or_update ON teldrive.files;
+DROP FUNCTION IF EXISTS teldrive.update_size_function;
+ALTER TABLE teldrive.files
+DROP COLUMN IF EXISTS trigger_executed;
+-- +goose StatementEnd