Inline plugin - iterating over items for album_fields significantly slows down operations

### Problem

Using even a simple `album_field` definition such as:

```yaml
album_fields:
album_bitrate: |
total = 0
for item in items:
total += item.bitrate
```

**_significantly_** degrades performance.

Without:
```
root@6ea1b5cf64a4:/# time beet move -p 'title:Von dutch'
Moving 3 items.
[...]

real 0m2.702s
user 0m4.211s
sys 0m0.399s
```

With:
```
Moving 3 items.
[...]

real 0m15.705s
user 0m5.028s
sys 0m1.892s
```

With more items, it was significantly worse:

w/o:
```
root@6ea1b5cf64a4:/# time beet move -p 'artist:Charli XCX'
Moving 175 items.
[...]

real 0m5.264s
user 0m6.991s
sys 0m0.467s
```

with: (I actually gave up letting it run)
```
Moving 175 items.
[...]
^CTraceback (most recent call last):
File "/lsiopy/lib/python3.12/site-packages/beets/ui/__init__.py", line 1870, in main
_raw_main(args)
File "/lsiopy/lib/python3.12/site-packages/beets/ui/__init__.py", line 1849, in _raw_main
subcommand.func(lib, suboptions, subargs)
File "/lsiopy/lib/python3.12/site-packages/beets/ui/commands.py", line 2216, in move_func
move_items(
File "/lsiopy/lib/python3.12/site-packages/beets/ui/commands.py", line 2146, in move_items
objs = [o for o in objs if (isalbummoved if album else isitemmoved)(o)]
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/lsiopy/lib/python3.12/site-packages/beets/ui/commands.py", line 2141, in isitemmoved
return item.path != item.destination(basedir=dest)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/lsiopy/lib/python3.12/site-packages/beets/library.py", line 1115, in destination
subpath = self.evaluate_template(subpath_tmpl, True)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/lsiopy/lib/python3.12/site-packages/beets/dbcore/db.py", line 701, in evaluate_template
return t.substitute(
^^^^^^^^^^^^^
File "/lsiopy/lib/python3.12/site-packages/beets/util/functemplate.py", line 559, in substitute
res = self.interpret(values, functions)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/lsiopy/lib/python3.12/site-packages/beets/util/functemplate.py", line 552, in interpret
return self.expr.evaluate(Environment(values, functions))
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/lsiopy/lib/python3.12/site-packages/beets/util/functemplate.py", line 240, in evaluate
out.append(part.evaluate(env))
^^^^^^^^^^^^^^^^^^
File "/lsiopy/lib/python3.12/site-packages/beets/util/functemplate.py", line 177, in evaluate
arg_vals = [expr.evaluate(env) for expr in self.args]
^^^^^^^^^^^^^^^^^^
File "/lsiopy/lib/python3.12/site-packages/beets/util/functemplate.py", line 240, in evaluate
out.append(part.evaluate(env))
^^^^^^^^^^^^^^^^^^
File "/lsiopy/lib/python3.12/site-packages/beets/util/functemplate.py", line 145, in evaluate
if self.ident in env.values:
^^^^^^^^^^^^^^^^^^^^^^^^
File "", line 813, in __contains__
File "/lsiopy/lib/python3.12/site-packages/beets/library.py", line 489, in __getitem__
value = self._get(key)
^^^^^^^^^^^^^^
File "/lsiopy/lib/python3.12/site-packages/beets/library.py", line 475, in _get
return self._get_formatted(self.album, key)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/lsiopy/lib/python3.12/site-packages/beets/dbcore/db.py", line 124, in _get_formatted
value = model._type(key).format(model.get(key))
^^^^^^^^^^^^^^
File "/lsiopy/lib/python3.12/site-packages/beets/dbcore/db.py", line 449, in _get
return getters[key](self)
^^^^^^^^^^^^^^^^^^
File "/lsiopy/lib/python3.12/site-packages/beetsplug/inline.py", line 120, in _func_func
func.__globals__.update(_dict_for(obj))
^^^^^^^^^^^^^^
File "/lsiopy/lib/python3.12/site-packages/beetsplug/inline.py", line 102, in _dict_for
out["items"] = list(obj.items())
^^^^^^^^^^^
File "/lsiopy/lib/python3.12/site-packages/beets/library.py", line 1295, in items
return self._db.items(dbcore.MatchQuery("album_id", self.id))
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/lsiopy/lib/python3.12/site-packages/beets/library.py", line 1697, in items
return self._fetch(Item, query, sort or self.get_default_item_sort())
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/lsiopy/lib/python3.12/site-packages/beets/library.py", line 1675, in _fetch
return super()._fetch(model_cls, query, sort)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/lsiopy/lib/python3.12/site-packages/beets/dbcore/db.py", line 1257, in _fetch
rows = tx.query(sql, subvals)
^^^^^^^^^^^^^^^^^^^^^^
File "/lsiopy/lib/python3.12/site-packages/beets/dbcore/db.py", line 956, in query
cursor = self.db._connection().execute(statement, subvals)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
KeyboardInterrupt

real 5m15.560s
user 0m19.222s
sys 0m36.162s
```

### Setup

* OS: Unraid/Docker (linuxserver.io image)
* Python version: Python 3.12.10
* beets version: beets version 2.3.0
* Turning off plugins made problem go away (yes/no): Yes

My configuration (output of `beet config`) is:

```yaml
directory: /music/music
# --------------- Main ---------------

library: /config/library.db
pluginpath: /config/plugins

# --------------- Plugins ---------------

plugins:
- embedart
- fetchart
- info
- albumtypes
- lastgenre
- yearfixer
- fromfilename
- mbsync
- mbsubmit
- unimported
- zero
- missing
- inline
- badfiles
- substitute
- duplicates
- importreplace
- web
- originquery

# --------------- Performance ---------------

threaded: yes

# --------------- UI ---------------

verbose: no

# --------------- Tagging ---------------

per_disc_numbering: yes

import:
log: /config/beet.log
write: yes
copy: no
move: yes
resume: yes
incremental: yes
incremental_skip_later: yes
quiet: no
quiet_fallback: skip
from_scratch: no
default_action: apply
none_rec_action: ask
duplicate_action: ask
autotag: yes
art_filename: folder
mbcollection:
auto: yes
collection: XXXX
remove: yes
musicbrainz:
user: XXXX
pass: XXXX
extra_tags:
- year
- catalognum
- country
- media
- label
zero:
fields: comments
auto: yes
keep_fields: []
update_database: no

# --------------- Import ---------------

clutter:
- Thumbs.DB
- Thumbs.db
- .DS_Store
- '**.zip'
- '**.torrent'
- '**.ini'
- '**.txt'
- '**.nfo'
- '**.m3u'
missing:
format: $albumartist - $album - $title
count: no
total: no
album: no

match:
strong_rec_thresh: 0.08
max_rec:
missing_tracks: medium
unmatched_tracks: medium
preferred:
countries:
- US
- XE
- JP
- GB|UK
media: [Digital Media|File, CD, SACD]
original_year: no
item_fields:
is_mp3_aac: 1 if format == "MP3" or format == "AAC" else 0
is_flac: 1 if format == "FLAC" else 0
disc0: disc
disctotal0: disctotal
album_fields:
title0: title
albumtypes:
types:
- ep: 'EP - '
- single: 'Single - '
- live: 'Live - '
- remix: 'Remix - '
bracket: ''
ignore_va: [compilation]
paths:
default: '%substitute{$albumartist}/($original_year) $albumartist - %ifdef{altalbum,$altalbum,$album}%ifdef{transtitle, [$transtitle]} [%ifdef{disambig,$disambig - }%if{$atypes,$atypes}${format}%if{$is_mp3_aac, - $album_bitrate}%if{$is_flac, - $max_bitdepth - $max_samplerate}]/%if{$multidisc,Disc $disc0/}${track} - %ifdef{alttitle,$alttitle,$title}'
collection::^.+: _Other/$collection/($original_year) $albumartist - %ifdef{altalbum,$altalbum,$album}%ifdef{transtitle, [$transtitle]} [%ifdef{disambig,$disambig - }${format}%if{$is_mp3_aac, - $album_bitrate}%if{$is_flac, - $max_bitdepth - $max_samplerate}]/%if{$multidisc,Disc $disc0/}${track} - %ifdef{alttitle,$alttitle,$title}
substitute:
bladee &.*: Bladee
blu &.*: Blu
bob dylan &.*: Bob Dylan
broadcast and.*: Broadcast
casiopea.*: Casiopea
czarface.*: Czarface
"death\u2019s dynamic shroud and.*": "death\u2019s dynamic shroud"
dizzy gillespie.*: Dizzy Gillespie
drake &.*: Drake
"el\u2010p feat.*": "El\u2010P"
evaboy.*: miya lowe
fred again...*: Fred again..
.*gene clark with.*: Gene Clark
gorillaz feat.*|spacemonkeyz &.*: Gorillaz
"Hiromi\u2019s Sonicbloom|\u4E0A\u539F\u3072\u308D\u307F \u30B6\u30FB\u30C8\u30EA\u30AA\u30FB\u30D7\u30ED\u30B8\u30A7\u30AF\u30C8": Hiromi
iglooghost.*: Iglooghost
"jay\u2010z &.*": "JAY\u2010Z"
john williams.*: John Williams
jpegmafia.*: JPEGMAFIA
"kanye west.*|kids see ghosts|\\\xA5\\$": Kanye West
laufey with.*: Laufey
macroblank &.*: Macroblank
mf doom &.*|jj doom|dangerdoom|viktor vaughn|king geedorah|nehruviandoom|westsidedoom: MF DOOM
neil young &.*: Neil Young
quasimoto: Madlib
rita lee &.*: Rita Lee
round table.*: Round Table
ryusenkei.*: Ryusenkei
saint pepsi.*: SAINT PEPSI
"Stan Getz & Jo\xE3o Gilberto.*": "Stan Getz & Jo\xE3o Gilberto"
Sufjan Stevens &.*: Sufjan Stevens
thaiboy digital &.*: Thaiboy Digital
the moody blues.*: The Moody Blues
the velvet underground.*: The Velvet Underground
.*tommy heavenly.*: "Tommy february\u2076"
trent reznor & atticus ross.*: Trent Reznor & Atticus Ross
yung lean &.*: Yung Lean
^(.*?)( & Madlib| & The Alchemist).*: \1

importreplace:
replacements: [{item_fields: artist artist_credit artists artists_credit composer, album_fields: artist artist_credit artists artists_credit composer, replace: {'Ye(?!\w)': Kanye West, 'Charli xcx(?!\w)': Charli XCX, 'RYUSENKEI(?!\w)': Ryusenkei}}, {item_fields: artist_sort artists_sort composer_sort, album_fields: artist_sort artists_sort composer_sort, replace: {'Ye(?!\w)': 'West, Kanye', 'Charli xcx(?!\w)': Charli XCX, 'RYUSENKEI(?!\w)': Ryusenkei}}]
fetchart:
auto: no
cover_names: folder cover front
minwidth: 500
maxwidth: 3000
high_resolution: yes
enforce_ratio: 0.5%
sources:
- filesystem
- itunes
- amazon
- albumart
- coverart: releasegroup
deinterlace: yes
cover_format: JPEG
quality: 98
max_filesize: 0
cautious: no
store_source: no
google_key: REDACTED
google_engine: REDACTED
fanarttv_key: REDACTED
lastfm_key: REDACTED
embedart:
auto: no
maxwidth: 720
quality: 95
compare_threshold: 0
ifempty: no
remove_art_file: no
unimported:
ignore_extensions: jpg png zip jepg log cue yaml db
ignore_subdirectories: []
lastgenre:
whitelist: /config/whitelist.txt
auto: no
canonical: yes
count: 5
fallback: ''
force: yes
min_weight: 10
prefer_specific: no
source: album
title_case: yes
separator: '; '
keep_existing: no
extended_debug: no
originquery:
origin_file: origin.yaml
tag_patterns:
media: $.Media
year: $."Edition year"
label: $."Record label"
catalognum: $."Catalog number"
albumdisambig: $.Edition
web:
host: 0.0.0.0
port: 8337
cors: ''
cors_supports_credentials: no
reverse_proxy: no
include_paths: no
readonly: yes
duplicates:
album: no
checksum: ''
copy: ''
count: no
delete: no
format: ''
full: no
keys: []
merge: no
move: ''
path: no
tiebreak: {}
strict: no
tag: ''
pathfields: {}
yearfixer:
auto: no
force: no
mbsubmit:
format: $track. $title - $artist ($length)
threshold: medium
picard_path: picard

```

Start with beetsplug/inline.py, especially _dict_for and _func_func, then follow the beet move path through beets/library.py and template evaluation in beets/dbcore/db.py. Reproduce the slowdown with the album_fields example and the provided beet move commands; done means the inline album-field case no longer causes the reported severe slowdown without changing its result.

Written by the indexing model from the issue text.