feat: SQLTarget connector instance shared with sinks

singer_sdk/target_base.py

@@ -28,8 +28,9 @@
 if t.TYPE_CHECKING:
     from pathlib import PurePath
 
+    from singer_sdk.connectors import SQLConnector
     from singer_sdk.mapper import PluginMapper
-    from singer_sdk.sinks import Sink
+    from singer_sdk.sinks import Sink, SQLSink
 
 _MAX_PARALLELISM = 8
 
@@ -48,7 +49,7 @@ class Target(PluginBase, SingerReader, metaclass=abc.ABCMeta):
 
     # Default class to use for creating new sink objects.
     # Required if `Target.get_sink_class()` is not defined.
-    default_sink_class: type[Sink] | None = None
+    default_sink_class: type[Sink]
 
     def __init__(
         self,
@@ -574,6 +575,23 @@ def get_singer_command(cls: type[Target]) -> click.Command:
 class SQLTarget(Target):
     """Target implementation for SQL destinations."""
 
+    _target_connector: SQLConnector | None = None
+
+    default_sink_class: type[SQLSink]
+
+    @property
+    def target_connector(self) -> SQLConnector:
+        """The connector object.
+
+        Returns:
+            The connector object.
+        """
+        if self._target_connector is None:
+            self._target_connector = self.default_sink_class.connector_class(
+                dict(self.config),
+            )
+        return self._target_connector
+
     @classproperty
     def capabilities(self) -> list[CapabilitiesEnum]:
         """Get target capabilities.
@@ -617,3 +635,114 @@ def _merge_missing(source_jsonschema: dict, target_jsonschema: dict) -> None:
         super().append_builtin_config(config_jsonschema)
 
     pass
+
+    @final
+    def add_sqlsink(
+        self,
+        stream_name: str,
+        schema: dict,
+        key_properties: list[str] | None = None,
+    ) -> Sink:
+        """Create a sink and register it.
+
+        This method is internal to the SDK and should not need to be overridden.
+
+        Args:
+            stream_name: Name of the stream.
+            schema: Schema of the stream.
+            key_properties: Primary key of the stream.
+
+        Returns:
+            A new sink for the stream.
+        """
+        self.logger.info("Initializing '%s' target sink...", self.name)
+        sink_class = self.get_sink_class(stream_name=stream_name)
+        sink = sink_class(
+            target=self,
+            stream_name=stream_name,
+            schema=schema,
+            key_properties=key_properties,
+            connector=self.target_connector,
+        )
+        sink.setup()
+        self._sinks_active[stream_name] = sink
+
+        return sink
+
+    def get_sink_class(self, stream_name: str) -> type[SQLSink]:
+        """Get sink for a stream.
+
+        Developers can override this method to return a custom Sink type depending
+        on the value of `stream_name`. Optional when `default_sink_class` is set.
+
+        Args:
+            stream_name: Name of the stream.
+
+        Raises:
+            ValueError: If no :class:`singer_sdk.sinks.Sink` class is defined.
+
+        Returns:
+            The sink class to be used with the stream.
+        """
+        if self.default_sink_class:
+            return self.default_sink_class
+
+        msg = (
+            f"No sink class defined for '{stream_name}' and no default sink class "
+            "available."
+        )
+        raise ValueError(msg)
+
+    def get_sink(
+        self,
+        stream_name: str,
+        *,
+        record: dict | None = None,
+        schema: dict | None = None,
+        key_properties: list[str] | None = None,
+    ) -> Sink:
+        """Return a sink for the given stream name.
+
+        A new sink will be created if `schema` is provided and if either `schema` or
+        `key_properties` has changed. If so, the old sink becomes archived and held
+        until the next drain_all() operation.
+
+        Developers only need to override this method if they want to provide a different
+        sink depending on the values within the `record` object. Otherwise, please see
+        `default_sink_class` property and/or the `get_sink_class()` method.
+
+        Raises :class:`singer_sdk.exceptions.RecordsWithoutSchemaException` if sink does
+        not exist and schema is not sent.
+
+        Args:
+            stream_name: Name of the stream.
+            record: Record being processed.
+            schema: Stream schema.
+            key_properties: Primary key of the stream.
+
+        Returns:
+            The sink used for this target.
+        """
+        _ = record  # Custom implementations may use record in sink selection.
+        if schema is None:
+            self._assert_sink_exists(stream_name)
+            return self._sinks_active[stream_name]
+
+        existing_sink = self._sinks_active.get(stream_name, None)
+        if not existing_sink:
+            return self.add_sqlsink(stream_name, schema, key_properties)
+
+        if (
+            existing_sink.schema != schema
+            or existing_sink.key_properties != key_properties
+        ):
+            self.logger.info(
+                "Schema or key properties for '%s' stream have changed. "
+                "Initializing a new '%s' sink...",
+                stream_name,
+                stream_name,
+            )
+            self._sinks_to_clear.append(self._sinks_active.pop(stream_name))
+            return self.add_sqlsink(stream_name, schema, key_properties)
+
+        return existing_sink

tests/conftest.py

@@ -10,9 +10,10 @@
 import pytest
 from sqlalchemy import __version__ as sqlalchemy_version
 
+from singer_sdk import SQLConnector
 from singer_sdk import typing as th
-from singer_sdk.sinks import BatchSink
-from singer_sdk.target_base import Target
+from singer_sdk.sinks import BatchSink, SQLSink
+from singer_sdk.target_base import SQLTarget, Target
 
 if t.TYPE_CHECKING:
     from _pytest.config import Config
@@ -116,3 +117,63 @@ def _write_state_message(self, state: dict):
         """Emit the stream's latest state."""
         super()._write_state_message(state)
         self.state_messages_written.append(state)
+
+
+class SQLConnectorMock(SQLConnector):
+    """A Mock SQLConnector class."""
+
+
+class SQLSinkMock(SQLSink):
+    """A mock Sink class."""
+
+    name = "sql-sink-mock"
+    connector_class = SQLConnectorMock
+
+    def __init__(
+        self,
+        target: SQLTargetMock,
+        stream_name: str,
+        schema: dict,
+        key_properties: list[str] | None,
+        connector: SQLConnector | None = None,
+    ):
+        """Create the Mock batch-based sink."""
+        self._connector: SQLConnector
+        self._connector = connector or self.connector_class(dict(target.config))
+        super().__init__(target, stream_name, schema, key_properties, connector)
+        self.target = target
+
+    def process_record(self, record: dict, context: dict) -> None:
+        """Tracks the count of processed records."""
+        self.target.num_records_processed += 1
+        super().process_record(record, context)
+
+    def process_batch(self, context: dict) -> None:
+        """Write to mock trackers."""
+        self.target.records_written.extend(context["records"])
+        self.target.num_batches_processed += 1
+
+    @property
+    def key_properties(self) -> list[str]:
+        return [key.upper() for key in super().key_properties]
+
+
+class SQLTargetMock(SQLTarget):
+    """A mock Target class."""
+
+    name = "sql-target-mock"
+    config_jsonschema = th.PropertiesList().to_dict()
+    default_sink_class = SQLSinkMock
+
+    def __init__(self, *args, **kwargs):
+        """Create the Mock target sync."""
+        super().__init__(*args, **kwargs)
+        self.state_messages_written: list[dict] = []
+        self.records_written: list[dict] = []
+        self.num_records_processed: int = 0
+        self.num_batches_processed: int = 0
+
+    def _write_state_message(self, state: dict):
+        """Emit the stream's latest state."""
+        super()._write_state_message(state)
+        self.state_messages_written.append(state)

tests/core/test_target_base.py

@@ -4,8 +4,11 @@
 
 import pytest
 
-from singer_sdk.exceptions import MissingKeyPropertiesError
-from tests.conftest import BatchSinkMock, TargetMock
+from singer_sdk.exceptions import (
+    MissingKeyPropertiesError,
+    RecordsWithoutSchemaException,
+)
+from tests.conftest import BatchSinkMock, SQLSinkMock, SQLTargetMock, TargetMock
 
 
 def test_get_sink():
@@ -53,3 +56,68 @@ def test_validate_record():
     # Test invalid record
     with pytest.raises(MissingKeyPropertiesError):
         sink._singer_validate_message({"name": "test"})
+
+
+def test_sql_get_sink():
+    input_schema_1 = {
+        "properties": {
+            "id": {
+                "type": ["string", "null"],
+            },
+            "col_ts": {
+                "format": "date-time",
+                "type": ["string", "null"],
+            },
+        },
+    }
+    input_schema_2 = copy.deepcopy(input_schema_1)
+    key_properties = []
+    target = SQLTargetMock(config={"sqlalchemy_url": "sqlite:///"})
+    sink = SQLSinkMock(
+        target=target,
+        stream_name="foo",
+        schema=input_schema_1,
+        key_properties=key_properties,
+        connector=target.target_connector,
+    )
+    target._sinks_active["foo"] = sink
+    sink_returned = target.get_sink(
+        "foo",
+        schema=input_schema_2,
+        key_properties=key_properties,
+    )
+    assert sink_returned is sink
+
+
+def test_add_sqlsink_and_get_sink():
+    input_schema_1 = {
+        "properties": {
+            "id": {
+                "type": ["string", "null"],
+            },
+            "col_ts": {
+                "format": "date-time",
+                "type": ["string", "null"],
+            },
+        },
+    }
+    input_schema_2 = copy.deepcopy(input_schema_1)
+    key_properties = []
+    target = SQLTargetMock(config={"sqlalchemy_url": "sqlite:///"})
+    sink = target.add_sqlsink(
+        "foo",
+        schema=input_schema_2,
+        key_properties=key_properties,
+    )
+
+    sink_returned = target.get_sink(
+        "foo",
+    )
+
+    assert sink_returned is sink
+
+    # Test invalid call
+    with pytest.raises(RecordsWithoutSchemaException):
+        target.get_sink(
+            "bar",
+        )