Add index to fix very slow rendering speed on low zoom levels.

api/migrations/versions/7868aed76122_add_overtaking_event_index.py

@@ -0,0 +1,26 @@
+"""add_overtaking_event_index
+
+
+Revision ID: 7868aed76122
+Revises: 587e69ecb466
+Create Date: 2023-07-16 13:37:17.694079
+
+"""
+from alembic import op
+import sqlalchemy as sa
+
+
+# revision identifiers, used by Alembic.
+revision = '7868aed76122'
+down_revision = '587e69ecb466'
+branch_labels = None
+depends_on = None
+
+
+def upgrade():
+    op.execute("CREATE INDEX IF NOT EXISTS ix_overtaking_event_geometry ON overtaking_event using GIST(geometry);")
+
+
+def downgrade():
+    op.drop_index("ix_overtaking_event_geometry")
+