feat(bigquery): add bigquery_drop_search_index sample to drop a search index from a table (#14732)

Problem:
The BigQuery documentation (https://cloud.google.com/bigquery/docs/search-index)
needs a standalone, tested Python code sample demonstrating how to
drop a search index from a table (region tag `bigquery_drop_search_index`).

Solution:
- Add `drop_search_index(project_id: str, dataset_id: str, table_id: str) -> None` in `bigquery/search/bigquery_drop_search_index.py`
  (Remove a search index from a BigQuery table using DROP SEARCH INDEX IF EXISTS.)
- Add unit tests (`bigquery/search/bigquery_drop_search_index_test.py`) covering both the success
  path and API error handling (`GoogleAPICallError`)

Author: iennae

bigquery/search/bigquery_drop_search_index.py

@@ -0,0 +1,67 @@
+# Copyright 2026 Google LLC
+#
+# Licensed 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
+#
+#     https://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.
+
+# [START bigquery_drop_search_index]
+import sys
+
+from google.api_core import exceptions
+from google.cloud import bigquery
+
+
+def drop_search_index(
+    project_id: str,
+    dataset_id: str,
+    table_id: str,
+) -> None:
+    """Drops a full-text search index from a BigQuery table.
+
+    Args:
+        project_id: Google Cloud project ID (for example, 'example-project').
+        dataset_id: BigQuery dataset ID containing the indexed table
+            (for example, 'example_dataset').
+        table_id: BigQuery table ID from which to drop the search index
+            (for example, 'example_table').
+    """
+    client = bigquery.Client(project=project_id)
+    # Target the example_search_index created on the table.
+    index_name = "example_search_index"
+    table_ref = f"{project_id}.{dataset_id}.{table_id}"
+    sql = f"DROP SEARCH INDEX IF EXISTS `{index_name}` ON `{table_ref}`;"
+
+    try:
+        print(f"Dropping search index {index_name} from table: {table_ref}")
+        query_job = client.query(sql)
+        query_job.result()
+    except exceptions.NotFound as err:
+        print(
+            f"error: table '{table_id}' or dataset '{dataset_id}' not found in "
+            f"project '{project_id}': {err.message}",
+            file=sys.stderr,
+        )
+        return
+    except exceptions.GoogleAPICallError as err:
+        print(
+            f"error: failed to drop search index '{index_name}' on table '{table_id}' "
+            f"in dataset '{dataset_id}' for project '{project_id}': {err.message}",
+            file=sys.stderr,
+        )
+        return
+
+    print(f"Resource ID: {table_ref}")
+    print(f"Index Name: {index_name}")
+    print(f"Job ID: {query_job.job_id}")
+    print(f"Statement Type: {query_job.statement_type}")
+
+
+# [END bigquery_drop_search_index]

bigquery/search/bigquery_drop_search_index_test.py

@@ -0,0 +1,70 @@
+# Copyright 2026 Google LLC
+#
+# Licensed 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
+#
+#     https://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 unittest import mock
+
+import bigquery_drop_search_index
+from google.api_core import exceptions
+import pytest
+
+
+def test_drop_search_index_success(
+    monkeypatch: pytest.MonkeyPatch,
+    capsys: pytest.CaptureFixture[str],
+) -> None:
+    mock_client = mock.MagicMock()
+    mock_job = mock.MagicMock()
+    mock_job.job_id = "example-job-123"
+    mock_job.statement_type = "SCRIPT"
+    mock_job.result.return_value = []
+    mock_client.query.return_value = mock_job
+    monkeypatch.setattr(
+        bigquery_drop_search_index.bigquery,
+        "Client",
+        lambda project=None: mock_client,
+    )
+
+    bigquery_drop_search_index.drop_search_index(
+        project_id="example-project",
+        dataset_id="example_dataset",
+        table_id="example_table",
+    )
+
+    captured = capsys.readouterr()
+    assert "Resource ID:" in captured.out
+    assert "example-project" in captured.out
+    assert mock_client.query.called
+
+
+def test_drop_search_index_error(
+    monkeypatch: pytest.MonkeyPatch,
+    capsys: pytest.CaptureFixture[str],
+) -> None:
+    mock_client = mock.MagicMock()
+    mock_client.query.side_effect = exceptions.NotFound("resource error")
+    monkeypatch.setattr(
+        bigquery_drop_search_index.bigquery,
+        "Client",
+        lambda project=None: mock_client,
+    )
+
+    bigquery_drop_search_index.drop_search_index(
+        project_id="example-project",
+        dataset_id="example_dataset",
+        table_id="example_table",
+    )
+
+    captured = capsys.readouterr()
+    assert "error:" in captured.err
+    assert "example-project" in captured.err