feat: implement InMemoryCatalog as a subclass of SqlCatalog (#1140)

closes: #1110

This PR implement a new catalog `InMemoryCatalog` as a subclass of
`SqlCatalog` with SQLite in-memory.

Author: hussein-awala

mkdocs/docs/configuration.md

@@ -388,6 +388,23 @@ catalog:
 | echo          | true                                                         | false   | SQLAlchemy engine [echo param](https://docs.sqlalchemy.org/en/20/core/engines.html#sqlalchemy.create_engine.params.echo) to log all statements to the default log handler                      |
 | pool_pre_ping | true                                                         | false   | SQLAlchemy engine [pool_pre_ping param](https://docs.sqlalchemy.org/en/20/core/engines.html#sqlalchemy.create_engine.params.pool_pre_ping) to test connections for liveness upon each checkout |
 
+### In Memory Catalog
+
+The in-memory catalog is built on top of `SqlCatalog` and uses SQLite in-memory database for its backend.
+
+It is useful for test, demo, and playground but not in production as it does not support concurrent access.
+
+```yaml
+catalog:
+  default:
+    type: in-memory
+    warehouse: /tmp/pyiceberg/warehouse
+```
+
+| Key       | Example                  | Default                       | Description                                                          |
+| --------- |--------------------------|-------------------------------|----------------------------------------------------------------------|
+| warehouse | /tmp/pyiceberg/warehouse | file:///tmp/iceberg/warehouse | The directory where the in-memory catalog will store its data files. |
+
 ### Hive Catalog
 
 ```yaml

pyiceberg/catalog/__init__.py

@@ -116,6 +116,7 @@ class CatalogType(Enum):
     GLUE = "glue"
     DYNAMODB = "dynamodb"
     SQL = "sql"
+    IN_MEMORY = "in-memory"
 
 
 def load_rest(name: str, conf: Properties) -> Catalog:
@@ -162,12 +163,22 @@ def load_sql(name: str, conf: Properties) -> Catalog:
         ) from exc
 
 
+def load_in_memory(name: str, conf: Properties) -> Catalog:
+    try:
+        from pyiceberg.catalog.memory import InMemoryCatalog
+
+        return InMemoryCatalog(name, **conf)
+    except ImportError as exc:
+        raise NotInstalledError("SQLAlchemy support not installed: pip install 'pyiceberg[sql-sqlite]'") from exc
+
+
 AVAILABLE_CATALOGS: dict[CatalogType, Callable[[str, Properties], Catalog]] = {
     CatalogType.REST: load_rest,
     CatalogType.HIVE: load_hive,
     CatalogType.GLUE: load_glue,
     CatalogType.DYNAMODB: load_dynamodb,
     CatalogType.SQL: load_sql,
+    CatalogType.IN_MEMORY: load_in_memory,
 }
 
 

pyiceberg/catalog/memory.py

@@ -0,0 +1,32 @@
+# Licensed to the Apache Software Foundation (ASF) under one
+# or more contributor license agreements.  See the NOTICE file
+# distributed with this work for additional information
+# regarding copyright ownership.  The ASF licenses this file
+# to you under the Apache License, Version 2.0 (the
+# "License"); you may not use this file except in compliance
+# with the License.  You may obtain a copy of the License at
+#
+#   http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing,
+# software distributed under the License is distributed on an
+# "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+# KIND, either express or implied.  See the License for the
+# specific language governing permissions and limitations
+# under the License.
+
+from pyiceberg.catalog.sql import SqlCatalog
+
+
+class InMemoryCatalog(SqlCatalog):
+    """
+    An in-memory catalog implementation that uses SqlCatalog with SQLite in-memory database.
+
+    This is useful for test, demo, and playground but not in production as it does not support concurrent access.
+    """
+
+    def __init__(self, name: str, warehouse: str = "file:///tmp/iceberg/warehouse", **kwargs: str) -> None:
+        self._warehouse_location = warehouse
+        if "uri" not in kwargs:
+            kwargs["uri"] = "sqlite:///:memory:"
+        super().__init__(name=name, warehouse=warehouse, **kwargs)