Syncing DB and FS about remote_media_cache

[jo-so]

I would like to remove entries from the (Postgres) database and the filesystem, if there's no matching counterpart. I would like to know if this is correct:

(
    psql -A -t -c "SELECT 'db ' || media_origin || '/'
      || substring(filesystem_id for 2) || '/'
      || substring(filesystem_id from 3 for 2) || '/'
      || substring(filesystem_id from 5)
    FROM remote_media_cache"

    find /var/lib/matrix-synapse/media/remote_content -type f -printf 'fs %P\n'
) |sort -t' ' -k2 |uniq -u -s3 | (
    list=
    while IFS=' ' read -r where what
    do
        case "$where" in
          fs) echo rm -v /var/lib/matrix-synapse/media/remote_content/$what;;
          db) list="${list:+$list,}'$what'";;
        esac
    done

    if test -n "$list"
    then
        psql_t -c "SELECT FROM remote_media_cache
          WHERE media_origin || filesystem_id IN ($(echo "$list" |tr -d /))"
    fi
)

(
    psql -A -t -c "SELECT 'db ' || media_origin || '/'
      || substring(filesystem_id for 2) || '/'
      || substring(filesystem_id from 3 for 2) || '/'
      || substring(filesystem_id from 5) || '/' || thumbnail_width || '-'
      || thumbnail_height || '-' || replace(thumbnail_type, '/', '-') || '-'
      || thumbnail_method
    FROM remote_media_cache_thumbnails"

    find /var/lib/matrix-synapse/media/remote_thumbnail -type f -printf 'fs %P\n'
) |sort -t' ' -k2 |uniq -u -s3 | (
    list=
    while IFS=' ' read -r where what
    do
        case "$where" in
          fs) echo rm -v /var/lib/matrix-synapse/media/remote_thumbnail/$what;;
          db) list="${list:+$list,}'$what'";;
        esac
    done

    if test -n "$list"
    then
        echo "SELECT FROM remote_media_cache_thumbnails
          WHERE media_origin || filesystem_id || thumbnail_width
            || thumbnail_height || replace(thumbnail_type, '/', '')
            || thumbnail_method IN ($(echo "$list" |tr -d /-))" |tee /tmp/query |psql_t
    fi
)

At me, this finds

• 0 entries in remote_media_cache not in the filesystem
• 103 entries in the filesystem not in remote_media_cache
• 28559 (out of 66183) in remote_media_cache_thumbnails missing in the filesystem
• 605 entries in the filesystem missing in remote_media_cache_thumbnails