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perf(db): partial index for the photos list query

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The default photos list (GET /api/v1/photos?per_page=N&sort=taken_at&order=desc)
filters NOT is_trashed AND NOT is_hidden and sorts by
(taken_at DESC NULLS LAST, id DESC). EXPLAIN on the 21k-row table
shows a seq-scan + top-N heapsort (~20ms standalone, multiplied under
concurrent fan-out on page load). The existing single-column
ix_photos_taken_at can't be used because the leading WHERE clause is
two booleans.

Partial index over the sort key, restricted to the visible subset.
Lets the planner index-scan in reverse and stop at LIMIT N.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
This commit is contained in:
Claudio
2026-05-10 21:28:28 +02:00
parent b1c3ee68dd
commit 1408ec3fa3
1 changed files with 40 additions and 0 deletions
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backend/alembic/versions/0017_photos_list_index.py Normal file
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"""Partial index for the photos list query
Revision ID: 0017_photos_list_index
Revises: 0016_nextcloud_integration
Create Date: 2026-05-10
The default photos-list query (GET /api/v1/photos?per_page=N&sort=taken_at&order=desc)
filters `NOT is_trashed AND NOT is_hidden` and sorts by
`(taken_at DESC NULLS LAST, id DESC)`. EXPLAIN ANALYZE on a 21k-row
table showed a seq-scan + top-N heapsort (~20ms standalone, worse under
concurrency) — Postgres can't use the single-column ix_photos_taken_at
when the leading WHERE clause is two booleans.
A partial index on the sort key, scoped to the visible subset, lets the
planner index-scan in reverse and stop at LIMIT N. Two booleans select
~95% of rows, so the partial predicate is tighter than the full table
without losing common queries.
"""
from typing import Sequence, Union
from alembic import op
revision: str = "0017_photos_list_index"
down_revision: Union[str, None] = "0016_nextcloud_integration"
branch_labels: Union[str, Sequence[str], None] = None
depends_on: Union[str, Sequence[str], None] = None
def upgrade() -> None:
op.execute(
"""
CREATE INDEX IF NOT EXISTS ix_photos_list_visible
ON photos (taken_at DESC NULLS LAST, id DESC)
WHERE NOT is_trashed AND NOT is_hidden
"""
)
def downgrade() -> None:
op.execute("DROP INDEX IF EXISTS ix_photos_list_visible")