update

layercake/layercake/dynamodb.py

@@ -228,6 +228,7 @@ class KeyPair(Key):
         *,
         rename_key: str | None = None,
         retain_key: bool = False,
+        table_name: str | None = None,
     ) -> None:
         """
         Initializes a composite key using partition and sort key.
@@ -242,11 +243,13 @@ class KeyPair(Key):
             If provided, renames the sort key in the output.
         retain_key : bool, optional
             Use the key itself as value if True; otherwise, use the extracted value.
+        table_name : str, optional
         """
 
         super().__init__(**{PK: pk, SK: sk})
         self._rename_key = rename_key
         self._retain_key = retain_key
+        self._table_name = table_name
 
     @property
     def rename_key(self) -> str | None:
@@ -256,6 +259,10 @@ class KeyPair(Key):
     def retain_key(self) -> bool:
         return self._retain_key
 
+    @property
+    def table_name(self) -> str | None:
+        return self._table_name
+
     def __repr__(self) -> str:
         pk, sk, *_ = self.values()
         return f'KeyPair({pk!r}, {sk!r})'
@@ -297,7 +304,12 @@ class KeyChain:
         if not isinstance(other, KeyPair):
             raise TypeError('Can only add a KeyPair to a KeyChain')
 
-        return KeyChain(pairs=self.pairs + (other,))
+        if other not in self.pairs:
+            pairs = self.pairs + (other,)
+        else:
+            pairs = self.pairs
+
+        return KeyChain(pairs=pairs)
 
 
 @dataclass(frozen=True)
@@ -311,6 +323,7 @@ class TransactKey:
     """
 
     pk: str
+    table_name: str | None = None
     pairs: tuple[KeyPair, ...] = ()
 
     def __add__(self, other: SortKey | KeyPair) -> 'TransactKey':
@@ -318,9 +331,18 @@ class TransactKey:
             raise TypeError('Can only add a SortKey and KeyPair to a TransactKey')
 
         if isinstance(other, SortKey):
-            other = KeyPair(self.pk, other)
+            other = KeyPair(self.pk, other, table_name=self.table_name)
 
-        return TransactKey(pk=self.pk, pairs=self.pairs + (other,))
+        if other not in self.pairs:
+            pairs = self.pairs + (other,)
+        else:
+            pairs = self.pairs
+
+        return TransactKey(
+            pk=self.pk,
+            table_name=self.table_name,
+            pairs=pairs,
+        )
 
 
 class TransactionCanceledReason(TypedDict):
@@ -884,6 +906,7 @@ class DynamoDBCollection:
         key: Key,
         *,
         ttl: int | datetime | None = None,
+        cond_expr: str | None = None,
         **kwargs: Any,
     ) -> bool:
         """Creates a new item, or replaces an old item with a new item.
@@ -895,6 +918,8 @@ class DynamoDBCollection:
         ttl: int or datetime, optional
             Time-to-live for the item, specified as a timestamp integer
             or datetime object.
+        cond_expr: str, optional
+            Conditional expression for deletion.
         **kwargs
             Additional data to be stored with the item.
 
@@ -909,7 +934,10 @@ class DynamoDBCollection:
         if isinstance(ttl, datetime):
             kwargs.update({'ttl': timestamp(ttl)})
 
-        return self.persistence_layer.put_item(item=key | kwargs)
+        return self.persistence_layer.put_item(
+            item=key | kwargs,
+            cond_expr=cond_expr,
+        )
 
     def delete_item(
         self,
@@ -1013,7 +1041,7 @@ class DynamoDBCollection:
         transact_items = [
             {
                 'Get': {
-                    'TableName': getattr(pair, 'table_name', table_name),
+                    'TableName': pair.table_name or table_name,
                     'Key': serialize(pair),
                 }
             }