Create index on download/data object association

This should speed up biosample search, since it returns download
statistics for each data object for each biosample.

nmdc_server/migrations/versions/2ec2d0b4f840_create_data_object_id_idx.py

@@ -0,0 +1,35 @@
+"""Create index on column `data_object_id` for table `bulk_download_data_object`
+
+Revision ID: 2ec2d0b4f840
+Revises: 5fb9910ca8e6
+Create Date: 2024-10-10 16:48:37.051479
+
+"""
+
+from typing import Optional
+
+import sqlalchemy as sa
+from alembic import op
+
+# revision identifiers, used by Alembic.
+revision: str = "2ec2d0b4f840"
+down_revision: Optional[str] = "5fb9910ca8e6"
+branch_labels: Optional[str] = None
+depends_on: Optional[str] = None
+
+
+def upgrade():
+    # ### commands auto generated by Alembic - please adjust! ###
+    op.create_index(
+        "bulk_download_data_object_id_idx",
+        "bulk_download_data_object",
+        ["data_object_id"],
+        unique=False,
+    )
+    # ### end Alembic commands ###
+
+
+def downgrade():
+    # ### commands auto generated by Alembic - please adjust! ###
+    op.drop_index("bulk_download_data_object_id_idx", table_name="bulk_download_data_object")
+    # ### end Alembic commands ###

nmdc_server/models.py

@@ -12,6 +12,7 @@
     Enum,
     Float,
     ForeignKey,
+    Index,
     Integer,
     LargeBinary,
     String,
@@ -834,6 +835,9 @@ class BulkDownloadDataObject(Base):
     )
 
 
+Index("bulk_download_data_object_id_idx", BulkDownloadDataObject.data_object_id)
+
+
 class EnvoTree(Base):
     __tablename__ = "envo_tree"