feat(benchmark): add run_profile timing harness

src/paperless_benchmark/harness.py

@@ -0,0 +1,50 @@
+# src/paperless_benchmark/harness.py
+from __future__ import annotations
+
+import time
+from dataclasses import dataclass
+from typing import TYPE_CHECKING
+from typing import Generic
+from typing import TypeVar
+
+from django.db import connection
+from django.test.utils import CaptureQueriesContext
+
+if TYPE_CHECKING:
+    from collections.abc import Callable
+
+T = TypeVar("T")
+
+
+@dataclass(frozen=True, slots=True)
+class ProfileResult(Generic[T]):
+    best_seconds: float
+    all_seconds: tuple[float, ...]
+    query_count: int
+    result: T
+
+
+def run_profile(fn: Callable[[], T], *, repeat: int = 5) -> ProfileResult[T]:
+    """
+    Call `fn` `repeat` times, capturing wall-clock time for every call and
+    the SQL query count for the final call. Returns the best (minimum)
+    time across all repeats, since the first call(s) can be skewed by
+    connection warm-up or cold caches.
+    """
+    all_seconds: list[float] = []
+    result: T | None = None
+    query_count = 0
+    for i in range(repeat):
+        with CaptureQueriesContext(connection) as ctx:
+            start = time.perf_counter()
+            result = fn()
+            all_seconds.append(time.perf_counter() - start)
+        if i == repeat - 1:
+            query_count = len(ctx.captured_queries)
+    assert result is not None  # repeat >= 1 guarantees at least one assignment
+    return ProfileResult(
+        best_seconds=min(all_seconds),
+        all_seconds=tuple(all_seconds),
+        query_count=query_count,
+        result=result,
+    )