Make SQLAlchemy optional for Postgres provider

providers/postgres/pyproject.toml

@@ -69,6 +69,9 @@ dependencies = [
 # The optional dependencies should be modified in place in the generated file
 # Any change in the dependencies is preserved when the file is regenerated
 [project.optional-dependencies]
+sqlalchemy = [
+    "sqlalchemy>=1.4.49"
+]
 "amazon" = [
     "apache-airflow-providers-amazon>=2.6.0",
 ]

providers/postgres/src/airflow/providers/postgres/hooks/postgres.py

@@ -27,7 +27,6 @@
 import psycopg2.extras
 from more_itertools import chunked
 from psycopg2.extras import DictCursor, NamedTupleCursor, RealDictCursor, execute_batch
-from sqlalchemy.engine import URL
 
 from airflow.exceptions import AirflowOptionalProviderFeatureException
 from airflow.providers.common.compat.sdk import AirflowException, Connection, conf
@@ -54,6 +53,7 @@
 if TYPE_CHECKING:
     from pandas import DataFrame as PandasDataFrame
     from polars import DataFrame as PolarsDataFrame
+    from sqlalchemy.engine import URL
 
     from airflow.providers.common.sql.dialects.dialect import Dialect
     from airflow.providers.openlineage.sqlparser import DatabaseInfo
@@ -167,6 +167,13 @@ def __cast_nullable(value, dst_type: type) -> Any:
 
     @property
     def sqlalchemy_url(self) -> URL:
+        try:
+            from sqlalchemy.engine import URL
+        except (ImportError, ModuleNotFoundError) as err:
+            raise AirflowOptionalProviderFeatureException(
+                "SQLAlchemy is not installed. Please install it with "
+                "`pip install apache-airflow-providers-postgres[sqlalchemy]`."
+            ) from err
         conn = self.connection
         query = conn.extra_dejson.get("sqlalchemy_query", {})
         if not isinstance(query, dict):