"""Traefik reads answered from the index alone

The rows page and the request chart read every raw row in the chosen range.
With only (router_name, scraped_at) indexed, each of those rows was a heap
fetch: a random disk read on a database whose indexes no longer fit in
memory, which took the rows page to 12-28 s. Carrying the charted columns
in the index makes these index-only scans; scraped_at gets an index of its
own for the request chart, which filters on time across every router.

Revision ID: traefik_004_covering_indexes
Revises: traefik_003_access_log
Create Date: 2026-10-08
"""
from typing import Sequence, Union
from alembic import op

revision: str = "traefik_004_covering_indexes"
down_revision: Union[str, None] = "traefik_003_access_log"
branch_labels: Union[str, Sequence[str], None] = None
depends_on: Union[str, Sequence[str], None] = None


def upgrade() -> None:
    op.drop_index("ix_traefik_metrics_router_scraped", "traefik_metrics")
    op.create_index("ix_traefik_metrics_router_scraped", "traefik_metrics", ["router_name", "scraped_at"],
                    postgresql_include=["request_rate", "latency_p95_ms", "error_rate_5xx_pct"])
    op.create_index("ix_traefik_metrics_scraped", "traefik_metrics", ["scraped_at"],
                    postgresql_include=["request_rate", "error_rate_5xx_pct"])


def downgrade() -> None:
    op.drop_index("ix_traefik_metrics_scraped", "traefik_metrics")
    op.drop_index("ix_traefik_metrics_router_scraped", "traefik_metrics")
    op.create_index("ix_traefik_metrics_router_scraped", "traefik_metrics", ["router_name", "scraped_at"])