moved functionality that is called multiple times to functions and an…

…d added code to pre_state_hook (#96)

target_bigquery/core.py

@@ -307,7 +307,7 @@ def __init__(
             self.config["project"],
         )
         self.client = bigquery_client_factory(self._credentials)
-        opts = {
+        self.table_opts = {
             "project": self.config["project"],
             "dataset": self.config["dataset"],
             "jsonschema": self.schema,
@@ -317,7 +317,7 @@ def __init__(
                 self.config.get("schema_resolver_version", 1)
             ),
         }
-        self.table = BigQueryTable(name=self.table_name, **opts)
+        self.table = BigQueryTable(name=self.table_name, **self.table_opts)
         self.create_target(key_properties=key_properties)
         self.update_schema()
         self.merge_target: Optional[BigQueryTable] = None
@@ -331,53 +331,37 @@ def __init__(
             and self._is_upsert_candidate()
         ):
             self.merge_target = copy(self.table)
-            self.table = BigQueryTable(
-                name=f"{self.table_name}__{time.strftime('%Y%m%d%H%M%S')}__{uuid.uuid4()}",
-                **opts,
-            )
-            self.table.create_table(
-                self.client,
-                self.apply_transforms,
-                **{
-                    "table": {
-                        "expires": datetime.datetime.now() + datetime.timedelta(days=1),
-                    },
-                    "dataset": {
-                        "location": self.config.get(
-                            "location",
-                            BigQueryTable.default_dataset_options()["location"],
-                        )
-                    },
-                },
-            )
-            time.sleep(2.5)  # Wait for eventual consistency
+            self._create_overwrite_table()
         elif self._is_overwrite_candidate():
             self.overwrite_target = copy(self.table)
-            self.table = BigQueryTable(
-                name=f"{self.table_name}__{time.strftime('%Y%m%d%H%M%S')}__{uuid.uuid4()}",
-                **opts,
-            )
-            self.table.create_table(
-                self.client,
-                self.apply_transforms,
-                **{
-                    "table": {
-                        "expires": datetime.datetime.now() + datetime.timedelta(days=1),
-                    },
-                    "dataset": {
-                        "location": self.config.get(
-                            "location",
-                            BigQueryTable.default_dataset_options()["location"],
-                        )
-                    },
-                },
-            )
-            time.sleep(2.5)  # Wait for eventual consistency
+            self._create_overwrite_table()
 
         self.global_par_typ = target.par_typ
         self.global_queue = target.queue
         self.increment_jobs_enqueued = target.increment_jobs_enqueued
 
+    def _create_overwrite_table(self) -> None:
+        self.table = BigQueryTable(
+            name=f"{self.table_name}__{time.strftime('%Y%m%d%H%M%S')}__{uuid.uuid4()}",
+            **self.table_opts,
+        )
+        self.table.create_table(
+            self.client,
+            self.apply_transforms,
+            **{
+                "table": {
+                    "expires": datetime.datetime.now() + datetime.timedelta(days=1),
+                },
+                "dataset": {
+                    "location": self.config.get(
+                        "location",
+                        BigQueryTable.default_dataset_options()["location"],
+                    )
+                },
+            },
+        )
+        time.sleep(2.5)  # Wait for eventual consistency
+
     def _is_upsert_candidate(self) -> bool:
         """Determine if this stream is an upsert candidate based on user configuration."""
         upsert_selection = self.config.get("upsert", False)
@@ -506,9 +490,21 @@ def update_schema(self) -> None:
         """Update the target schema in BigQuery."""
         pass
 
+    def _get_bigquery_client(self) -> bigquery.Client:
+        # If gcs_stage method was used, self.client is probably
+        # an instance of storage.Client, instead of bigquery.Client
+        return (
+            self.client
+            if isinstance(self.client, bigquery.Client)
+            else bigquery_client_factory(self._credentials)
+        )
+
     def pre_state_hook(self) -> None:
-        """Called before state is emitted to stdout."""
-        pass
+        # if we have a merge_target we need to merge the table before writing out state
+        # otherwise we might end up with state being moved forward without data being written.
+        if self.merge_target:
+            self.merge_table(bigquery_client=self._get_bigquery_client())
+            self._create_overwrite_table()
 
     @staticmethod
     @abstractmethod
@@ -518,49 +514,48 @@ def worker_cls_factory(
         """Return a worker class for the given parallelization type."""
         raise NotImplementedError
 
+    def merge_table(self, bigquery_client:bigquery.Client) -> None:
+        target = self.merge_target.as_table()
+        date_columns = ["_sdc_extracted_at", "_sdc_received_at"]
+        tmp, ctas_tmp = None, "SELECT 1 AS _no_op"
+        if self._is_dedupe_before_upsert_candidate():
+            # We can't use MERGE with a non-unique key, so we need to dedupe the temp table into
+            # a _SESSION scoped intermediate table.
+            tmp = f"{self.merge_target.name}__tmp"
+            dedupe_query = (
+                f"SELECT * FROM {self.table.get_escaped_name()} "
+                f"QUALIFY ROW_NUMBER() OVER (PARTITION BY {', '.join(f'`{p}`' for p in self.key_properties)} "
+                f"ORDER BY COALESCE({', '.join(date_columns)}) DESC) = 1"
+            )
+            ctas_tmp = f"CREATE OR REPLACE TEMP TABLE `{tmp}` AS {dedupe_query}"
+        merge_clause = (
+                f"MERGE `{self.merge_target}` AS target USING `{tmp or self.table}` AS source ON "
+                + " AND ".join(
+            f"target.`{f}` = source.`{f}`" for f in self.key_properties
+        )
+        )
+        update_clause = "UPDATE SET " + ", ".join(
+            f"target.`{f.name}` = source.`{f.name}`" for f in target.schema
+        )
+        insert_clause = (
+            f"INSERT ({', '.join(f'`{f.name}`' for f in target.schema)}) "
+            f"VALUES ({', '.join(f'source.`{f.name}`' for f in target.schema)})"
+        )
+        bigquery_client.query(
+            f"{ctas_tmp}; {merge_clause} "
+            f"WHEN MATCHED THEN {update_clause} "
+            f"WHEN NOT MATCHED THEN {insert_clause}; "
+            f"DROP TABLE IF EXISTS {self.table.get_escaped_name()};"
+        ).result()
+
     def clean_up(self) -> None:
         """Clean up the target table."""
         # If gcs_stage method was used, self.client is probably
         # an instance of storage.Client, instead of bigquery.Client
-        bigquery_client = (
-            self.client
-            if isinstance(self.client, bigquery.Client)
-            else bigquery_client_factory(self._credentials)
-        )
+        bigquery_client = self._get_bigquery_client()
         if self.merge_target is not None:
             # We must merge the temp table into the target table.
-            target = self.merge_target.as_table()
-            date_columns = ["_sdc_extracted_at", "_sdc_received_at"]
-            tmp, ctas_tmp = None, "SELECT 1 AS _no_op"
-            if self._is_dedupe_before_upsert_candidate():
-                # We can't use MERGE with a non-unique key, so we need to dedupe the temp table into
-                # a _SESSION scoped intermediate table.
-                tmp = f"{self.merge_target.name}__tmp"
-                dedupe_query = (
-                    f"SELECT * FROM {self.table.get_escaped_name()} "
-                    f"QUALIFY ROW_NUMBER() OVER (PARTITION BY {', '.join(f'`{p}`' for p in self.key_properties)} "
-                    f"ORDER BY COALESCE({', '.join(date_columns)}) DESC) = 1"
-                )
-                ctas_tmp = f"CREATE OR REPLACE TEMP TABLE `{tmp}` AS {dedupe_query}"
-            merge_clause = (
-                f"MERGE `{self.merge_target}` AS target USING `{tmp or self.table}` AS source ON "
-                + " AND ".join(
-                    f"target.`{f}` = source.`{f}`" for f in self.key_properties
-                )
-            )
-            update_clause = "UPDATE SET " + ", ".join(
-                f"target.`{f.name}` = source.`{f.name}`" for f in target.schema
-            )
-            insert_clause = (
-                f"INSERT ({', '.join(f'`{f.name}`' for f in target.schema)}) "
-                f"VALUES ({', '.join(f'source.`{f.name}`' for f in target.schema)})"
-            )
-            bigquery_client.query(
-                f"{ctas_tmp}; {merge_clause} "
-                f"WHEN MATCHED THEN {update_clause} "
-                f"WHEN NOT MATCHED THEN {insert_clause}; "
-                f"DROP TABLE IF EXISTS {self.table.get_escaped_name()};"
-            ).result()
+            self.merge_table(bigquery_client=bigquery_client)
             self.table = self.merge_target
             self.merge_target = None
         elif self.overwrite_target is not None:
@@ -574,7 +569,7 @@ def clean_up(self) -> None:
                 f" {self.table.get_escaped_name()};"
             ).result()
             self.table = cast(BigQueryTable, self.merge_target)
-            self.merge_target = None
+            self.overwrite_target = None
 
 
 class Denormalized: