Count runs per flow, and page the run list by offset

backend/fluksio/api/routes/runs.py

@@ -10,6 +10,8 @@ from typing import Any
 from fastapi import APIRouter, Depends, HTTPException, Request
 from fastapi.concurrency import run_in_threadpool
 from pydantic import BaseModel, Field
+from sqlalchemy import func
+from sqlalchemy import select as sa_select
 from sqlmodel import col, select
 
 from fluksio.api.deps import CurrentUser, SessionDep, get_current_user
@@ -98,6 +100,16 @@ class RunDetail(RunRow):
     artifacts: list[ArtifactRow] = Field(default_factory=list)
 
 
+class FlowRunsRow(BaseModel):
+    """How much a flow has been run, for the screen's list of flows."""
+
+    flow: str
+    runs: int
+    running: int
+    queued: int
+    last_created_at: Any = None
+
+
 class MetricPoint(BaseModel):
     step: int
     ts: float
@@ -197,6 +209,7 @@ def read_runs(
     group: str | None = None,
     digest: str | None = None,
     limit: int = 50,
+    offset: int = 0,
 ) -> Any:
     """Runs, newest first. The queryable table an experiment log needs."""
     statement = select(Run).order_by(col(Run.created_at).desc())
@@ -208,7 +221,35 @@ def read_runs(
         statement = statement.where(col(Run.group_id) == group)
     if digest:
         statement = statement.where(col(Run.params_digest) == digest)
-    return list(session.exec(statement.limit(min(limit, 500))))
+    statement = statement.offset(max(0, offset)).limit(min(limit, 500))
+    return list(session.exec(statement))
+
+
+@router.get("/overview", response_model=list[FlowRunsRow])
+def read_overview(session: SessionDep) -> Any:
+    """One row per flow that has ever run, busiest-recent first.
+
+    The list caps at 500 newest runs, so counting flows on the client goes
+    wrong the moment a history outgrows one page. The database counts instead.
+    """
+    statement = sa_select(
+        col(Run.flow),
+        col(Run.status),
+        func.count(col(Run.id)),
+        func.max(col(Run.created_at)),
+    ).group_by(col(Run.flow), col(Run.status))
+
+    rows: dict[str, FlowRunsRow] = {}
+    for flow, status, count, latest in session.execute(statement):
+        row = rows.setdefault(flow, FlowRunsRow(flow=flow, runs=0, running=0, queued=0))
+        row.runs += count
+        if status == "running":
+            row.running += count
+        elif status == "queued":
+            row.queued += count
+        if row.last_created_at is None or latest > row.last_created_at:
+            row.last_created_at = latest
+    return sorted(rows.values(), key=lambda row: row.last_created_at, reverse=True)
 
 
 @router.get("/{run_id}", response_model=RunDetail)