actually make filters work right

dynamodb/update_item.odin

@@ -0,0 +1,125 @@
+// update_item.odin — Storage layer UpdateItem operation
+// This file lives in the dynamodb/ package alongside storage.odin
+package dynamodb
+
+import "core:strings"
+import "core:sync"
+import "../rocksdb"
+
+// UpdateItem — fetch existing item, apply update plan, write back
+// Uses EXCLUSIVE lock (write operation)
+//
+// Returns:
+//   - old_item:  the item BEFORE mutations (if it existed), for ReturnValues
+//   - new_item:  the item AFTER mutations
+//   - error
+update_item :: proc(
+	engine: ^Storage_Engine,
+	table_name: string,
+	key_item: Item,
+	plan: ^Update_Plan,
+) -> (old_item: Maybe(Item), new_item: Maybe(Item), err: Storage_Error) {
+	table_lock := get_or_create_table_lock(engine, table_name)
+	sync.rw_mutex_lock(table_lock)
+	defer sync.rw_mutex_unlock(table_lock)
+
+	// Get table metadata
+	metadata, meta_err := get_table_metadata(engine, table_name)
+	if meta_err != .None {
+		return nil, nil, meta_err
+	}
+	defer table_metadata_destroy(&metadata, engine.allocator)
+
+	// Extract key from the provided key item
+	key_struct, key_ok := key_from_item(key_item, metadata.key_schema)
+	if !key_ok {
+		return nil, nil, .Missing_Key_Attribute
+	}
+	defer key_destroy(&key_struct)
+
+	// Get key values
+	key_values, kv_ok := key_get_values(&key_struct)
+	if !kv_ok {
+		return nil, nil, .Invalid_Key
+	}
+
+	// Build storage key
+	storage_key := build_data_key(table_name, key_values.pk, key_values.sk)
+	defer delete(storage_key)
+
+	// Fetch existing item (if any)
+	existing_encoded, get_err := rocksdb.db_get(&engine.db, storage_key)
+	existing_item: Item
+
+	if get_err == .None && existing_encoded != nil {
+		defer delete(existing_encoded)
+
+		decoded, decode_ok := decode(existing_encoded)
+		if !decode_ok {
+			return nil, nil, .Serialization_Error
+		}
+		existing_item = decoded
+		// Save old item for ReturnValues
+		old_item = item_deep_copy(existing_item)
+	} else if get_err == .NotFound || existing_encoded == nil {
+		// Item doesn't exist yet — start with just the key attributes
+		existing_item = make(Item)
+
+		for ks in metadata.key_schema {
+			if val, found := key_item[ks.attribute_name]; found {
+				existing_item[strings.clone(ks.attribute_name)] = attr_value_deep_copy(val)
+			}
+		}
+	} else {
+		return nil, nil, .RocksDB_Error
+	}
+
+	// Apply update plan
+	if !execute_update_plan(&existing_item, plan) {
+		item_destroy(&existing_item)
+		if old, has := old_item.?; has {
+			old_copy := old
+			item_destroy(&old_copy)
+		}
+		return nil, nil, .Invalid_Key
+	}
+
+	// Validate key attributes are still present and correct type
+	validation_err := validate_item_key_types(
+		existing_item, metadata.key_schema, metadata.attribute_definitions,
+	)
+	if validation_err != .None {
+		item_destroy(&existing_item)
+		if old, has := old_item.?; has {
+			old_copy := old
+			item_destroy(&old_copy)
+		}
+		return nil, nil, validation_err
+	}
+
+	// Encode updated item
+	encoded_item, encode_ok := encode(existing_item)
+	if !encode_ok {
+		item_destroy(&existing_item)
+		if old, has := old_item.?; has {
+			old_copy := old
+			item_destroy(&old_copy)
+		}
+		return nil, nil, .Serialization_Error
+	}
+	defer delete(encoded_item)
+
+	// Write back to RocksDB
+	put_err := rocksdb.db_put(&engine.db, storage_key, encoded_item)
+	if put_err != .None {
+		item_destroy(&existing_item)
+		if old, has := old_item.?; has {
+			old_copy := old
+			item_destroy(&old_copy)
+		}
+		return nil, nil, .RocksDB_Error
+	}
+
+	new_item = existing_item
+	return old_item, new_item, .None
+}