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siftlode/backend/tests/test_channel_list_index_only.py
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peter 4aaaaa7860 chore(comments): drop epic, sprint and review-round ids from the code
The code cited its plan instead of saying why: `E28 review J4`, `(R6 S3b)`, `S1 justified…`,
`deep-review round 5`. That plan lives in the private ops repo, so for every reader of this one the
citation was noise, and a sentence whose subject was the plan step ("round 2 showed…") hid its
lesson behind an id. Each one is gone and the "why" kept: a bare citation is deleted, a sentence
carrying a lesson is reworded around it ("a later attempt showed…").

Measured (`scripts/audit_metrics.py`, product code): 652 lines in 270 files carried an epic code by
the definition the next commit holds (507 / 241 by the old, two-digit-only one) -> 0. Across all
code, tests, scripts and configs: ~1100 epic-code lines plus ~320 sprint/round ids.

Behaviour unchanged, checked mechanically: every changed .py file has the same AST once docstrings
are blanked; css/sh/toml/yml/json files are identical once comments are stripped; the only
non-comment changes in TS/JS are test titles, one description string in a contract table, and five
ESLint messages, whose text is all the gates snapshot diff holds. Not touched: Markdown (docs and
the changelog keep their history), Alembic migrations, TV episode notation (`S2 · E5`), DESIGN.md
ids (`C1`, `B4`, `S3h`), tracker ids (`SEC-16`, `DX-17`).

One stale claim fixed on the way: test_hls_reaper's docstring said the player checkpoints "every
10 s whether or not it is playing", which plex/stream.py calls wrong; it now says what the code does.
2026-10-05 00:19:39 +02:00

84 lines
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"""The channel manager's sums and the feed sidebar's counts read the index alone.
`GET /api/channels` counts each subscribed channel's videos and sums their durations; `/feed/summary`
and `/feed/years` count the reader's videos per channel and per year under the default filters. They
used to read every video's heap page for that (681 MB on prod), a 2–6 s first open once something else
had pushed the table out of memory. Migration 0095 makes `ix_videos_channel_pub_cover` carry every
column those queries read, so Postgres answers them with Index Only Scans. This test holds the queries
and the index together: a column added to one and not the other fails it. DB lane.
"""
import re
from sqlalchemy import text
from sqlalchemy.dialects import postgresql
from app.feedquery import filtered_query
from app.models import Video
from app.routes.channels import channel_aggregates
INDEX = "ix_videos_channel_pub_cover"
# The feed's own defaults (routes/feed.py _feed_params): what the sidebar asks on a plain open.
FEED_DEFAULTS = {
"tags": [],
"tag_modes": {"language": "or", "topic": "or", "other": "or"},
"untagged": False,
"channel_ids": [],
"q": None,
"min_duration": None,
"max_duration": None,
"max_age_days": None,
"published_after": None,
"published_before": None,
"show_normal": True,
"include_shorts": False,
"include_live": False,
"show": "unwatched",
"scope": "my",
"library_source": "organic",
}
def _index_columns(db) -> list[str]:
# Key columns first, then the INCLUDE ones, in the index's own order.
return list(
db.execute(
text(
"SELECT a.attname FROM pg_index i "
"JOIN pg_class c ON c.oid = i.indexrelid "
"CROSS JOIN LATERAL unnest(i.indkey) WITH ORDINALITY AS k(attnum, n) "
"JOIN pg_attribute a ON a.attrelid = i.indrelid AND a.attnum = k.attnum "
"WHERE c.relname = :name ORDER BY k.n"
),
{"name": INDEX},
).scalars()
)
def _video_columns(stmt) -> set[str]:
# The columns of `videos` the statement as SENT reads: the compiled SQL, not the expression tree,
# which still carries the projection a with_only_columns replaced.
sql = str(stmt.compile(dialect=postgresql.dialect()))
return set(re.findall(r"\bvideos\.(\w+)", sql))
def _assert_covered(db, read: set[str]) -> None:
held = _index_columns(db)
assert held, f"{INDEX} is missing"
# It leads with channel_id, so it also serves every per-channel lookup the old index did.
assert held[0] == "channel_id"
assert read <= set(held), f"read but not in {INDEX}: {sorted(read - set(held))}"
def test_the_channel_sums_read_only_columns_the_index_holds(db):
_assert_covered(db, _video_columns(channel_aggregates(["UC_x"])))
def test_the_feed_sidebar_counts_read_only_columns_the_index_holds(db, make_user):
# feed_summary groups the default filter by channel, feed_years by publish date.
base, _rank = filtered_query(db, make_user(), **FEED_DEFAULTS)
_assert_covered(
db, _video_columns(base.with_only_columns(Video.channel_id, Video.published_at))
)