speedup exact words

[MarinPostma]

This PR make exact_words return an Option instead of an empty set, since set creation is costly, as noticed by @Kerollmops.

I was not convinces that this was the cause for all of the performance drop we measured, and then realized that methods that initialized it were called recursively which caused initialization times to add up. While the first fix solves the issue when not using exact words, using exact word remained way more expensive that it should be. To address this issue, the exact words are cached into the Context, so they are only initialized once.

[Kerollmops]

Could you please run the search benchmarks on this branch? This way we will see the changes!

[MarinPostma]

group                                                                                                    search_songs_main_9f78e392             search_songs_speedup-exact-words_25fc5766
-----                                                                                                    --------------------------             -----------------------------------------
smol-songs.csv: asc + default/Notstandskomitee                                                           1.01      3.6±0.02ms        ? ?/sec    1.00      3.6±0.03ms        ? ?/sec
smol-songs.csv: asc + default/charles                                                                    1.05      2.5±0.01ms        ? ?/sec    1.00      2.4±0.01ms        ? ?/sec
smol-songs.csv: asc + default/charles mingus                                                             1.18      4.0±0.02ms        ? ?/sec    1.00      3.4±0.01ms        ? ?/sec
smol-songs.csv: asc + default/david                                                                      1.04      3.4±0.01ms        ? ?/sec    1.00      3.2±0.01ms        ? ?/sec
smol-songs.csv: asc + default/david bowie                                                                1.11      5.5±0.02ms        ? ?/sec    1.00      4.9±0.02ms        ? ?/sec
smol-songs.csv: asc + default/john                                                                       1.04      3.7±0.01ms        ? ?/sec    1.00      3.5±0.02ms        ? ?/sec
smol-songs.csv: asc + default/marcus miller                                                              1.12      6.1±0.02ms        ? ?/sec    1.00      5.5±0.03ms        ? ?/sec
smol-songs.csv: asc + default/michael jackson                                                            1.11      5.5±0.02ms        ? ?/sec    1.00      5.0±0.02ms        ? ?/sec
smol-songs.csv: asc + default/tamo                                                                       1.10  1706.7±15.65µs        ? ?/sec    1.00  1552.0±11.03µs        ? ?/sec
smol-songs.csv: asc + default/thelonious monk                                                            1.08      5.7±0.02ms        ? ?/sec    1.00      5.3±0.02ms        ? ?/sec
smol-songs.csv: asc/Notstandskomitee                                                                     1.02      3.3±0.02ms        ? ?/sec    1.00      3.2±0.01ms        ? ?/sec
smol-songs.csv: asc/charles                                                                              1.28    678.5±3.86µs        ? ?/sec    1.00   530.2±12.36µs        ? ?/sec
smol-songs.csv: asc/charles mingus                                                                       1.56  1409.0±40.88µs        ? ?/sec    1.00    903.5±4.18µs        ? ?/sec
smol-songs.csv: asc/david                                                                                1.18    963.3±4.31µs        ? ?/sec    1.00    816.2±8.37µs        ? ?/sec
smol-songs.csv: asc/david bowie                                                                          1.39  1722.6±39.79µs        ? ?/sec    1.00   1238.6±8.40µs        ? ?/sec
smol-songs.csv: asc/john                                                                                 1.20    849.6±3.28µs        ? ?/sec    1.00    707.9±5.37µs        ? ?/sec
smol-songs.csv: asc/marcus miller                                                                        1.43   1635.8±8.91µs        ? ?/sec    1.00  1142.0±17.96µs        ? ?/sec
smol-songs.csv: asc/michael jackson                                                                      1.41  1684.4±18.05µs        ? ?/sec    1.00  1192.5±12.75µs        ? ?/sec
smol-songs.csv: asc/tamo                                                                                 2.73    231.0±1.57µs        ? ?/sec    1.00     84.5±0.84µs        ? ?/sec
smol-songs.csv: asc/thelonious monk                                                                      1.15      4.0±0.02ms        ? ?/sec    1.00      3.5±0.02ms        ? ?/sec
smol-songs.csv: basic filter: <=/Notstandskomitee                                                        2.01   298.6±16.12µs        ? ?/sec    1.00   148.5±11.89µs        ? ?/sec
smol-songs.csv: basic filter: <=/charles                                                                 3.97    193.7±1.28µs        ? ?/sec    1.00     48.9±0.46µs        ? ?/sec
smol-songs.csv: basic filter: <=/charles mingus                                                          5.76    604.8±6.50µs        ? ?/sec    1.00    105.0±0.85µs        ? ?/sec
smol-songs.csv: basic filter: <=/david                                                                   4.49    185.3±1.67µs        ? ?/sec    1.00     41.2±0.61µs        ? ?/sec
smol-songs.csv: basic filter: <=/david bowie                                                             6.78    579.2±6.94µs        ? ?/sec    1.00     85.4±0.99µs        ? ?/sec
smol-songs.csv: basic filter: <=/john                                                                    5.28    180.4±2.24µs        ? ?/sec    1.00     34.2±0.26µs        ? ?/sec
smol-songs.csv: basic filter: <=/marcus miller                                                           6.26    601.8±6.72µs        ? ?/sec    1.00     96.1±0.70µs        ? ?/sec
smol-songs.csv: basic filter: <=/michael jackson                                                         5.48    615.3±4.05µs        ? ?/sec    1.00    112.3±0.96µs        ? ?/sec
smol-songs.csv: basic filter: <=/tamo                                                                    5.26    180.7±1.13µs        ? ?/sec    1.00     34.4±0.43µs        ? ?/sec
smol-songs.csv: basic filter: <=/thelonious monk                                                         3.99    630.8±5.85µs        ? ?/sec    1.00    158.0±1.40µs        ? ?/sec
smol-songs.csv: basic filter: TO/Notstandskomitee                                                        2.09   294.8±14.58µs        ? ?/sec    1.00    140.9±0.96µs        ? ?/sec
smol-songs.csv: basic filter: TO/charles                                                                 3.92    192.8±2.70µs        ? ?/sec    1.00     49.2±0.39µs        ? ?/sec
smol-songs.csv: basic filter: TO/charles mingus                                                          5.72    610.2±4.74µs        ? ?/sec    1.00    106.6±1.24µs        ? ?/sec
smol-songs.csv: basic filter: TO/david                                                                   4.49    189.5±1.35µs        ? ?/sec    1.00     42.2±0.41µs        ? ?/sec
smol-songs.csv: basic filter: TO/david bowie                                                             6.69    581.2±5.23µs        ? ?/sec    1.00     86.9±0.65µs        ? ?/sec
smol-songs.csv: basic filter: TO/john                                                                    5.15    182.6±1.73µs        ? ?/sec    1.00     35.5±0.39µs        ? ?/sec
smol-songs.csv: basic filter: TO/marcus miller                                                           6.14    590.3±7.96µs        ? ?/sec    1.00     96.1±0.93µs        ? ?/sec
smol-songs.csv: basic filter: TO/michael jackson                                                         5.33    600.4±4.35µs        ? ?/sec    1.00    112.5±0.96µs        ? ?/sec
smol-songs.csv: basic filter: TO/tamo                                                                    5.23    181.9±1.46µs        ? ?/sec    1.00     34.8±0.53µs        ? ?/sec
smol-songs.csv: basic filter: TO/thelonious monk                                                         4.30    641.0±8.20µs        ? ?/sec    1.00    149.2±6.64µs        ? ?/sec
smol-songs.csv: basic placeholder/                                                                       1.04     61.4±0.32µs        ? ?/sec    1.00     59.2±0.47µs        ? ?/sec
smol-songs.csv: basic with quote/"Notstandskomitee"                                                      1.00    204.0±1.54µs        ? ?/sec    1.02    208.7±1.45µs        ? ?/sec
smol-songs.csv: basic with quote/"charles"                                                               1.00    173.1±1.12µs        ? ?/sec    1.02    177.3±1.56µs        ? ?/sec
smol-songs.csv: basic with quote/"charles" "mingus"                                                      1.00  1269.4±10.77µs        ? ?/sec    1.01  1288.0±12.00µs        ? ?/sec
smol-songs.csv: basic with quote/"david"                                                                 1.00    247.2±1.73µs        ? ?/sec    1.01    249.2±1.45µs        ? ?/sec
smol-songs.csv: basic with quote/"david" "bowie"                                                         1.00  1436.9±10.27µs        ? ?/sec    1.00   1438.4±8.40µs        ? ?/sec
smol-songs.csv: basic with quote/"john"                                                                  1.00    362.7±2.56µs        ? ?/sec    1.01    365.9±4.02µs        ? ?/sec
smol-songs.csv: basic with quote/"marcus" "miller"                                                       1.00    306.1±1.76µs        ? ?/sec    1.01    309.5±1.92µs        ? ?/sec
smol-songs.csv: basic with quote/"michael" "jackson"                                                     1.00   1442.3±7.33µs        ? ?/sec    1.00   1441.7±7.51µs        ? ?/sec
smol-songs.csv: basic with quote/"tamo"                                                                  1.00    555.9±3.43µs        ? ?/sec    1.00   556.4±16.79µs        ? ?/sec
smol-songs.csv: basic with quote/"thelonious" "monk"                                                     1.00   1752.4±7.07µs        ? ?/sec    1.00  1752.7±11.03µs        ? ?/sec
smol-songs.csv: basic without quote/Notstandskomitee                                                     1.05      3.5±0.03ms        ? ?/sec    1.00      3.3±0.02ms        ? ?/sec
smol-songs.csv: basic without quote/charles                                                              1.48    436.0±3.54µs        ? ?/sec    1.00    295.4±1.98µs        ? ?/sec
smol-songs.csv: basic without quote/charles mingus                                                       1.19      3.6±0.01ms        ? ?/sec    1.00      3.1±0.07ms        ? ?/sec
smol-songs.csv: basic without quote/david                                                                1.33    591.5±3.88µs        ? ?/sec    1.00    446.4±4.42µs        ? ?/sec
smol-songs.csv: basic without quote/david bowie                                                          1.08      6.9±0.03ms        ? ?/sec    1.00      6.4±0.02ms        ? ?/sec
smol-songs.csv: basic without quote/john                                                                 1.10  1432.4±14.73µs        ? ?/sec    1.00   1299.2±9.68µs        ? ?/sec
smol-songs.csv: basic without quote/marcus miller                                                        1.19      3.1±0.01ms        ? ?/sec    1.00      2.6±0.01ms        ? ?/sec
smol-songs.csv: basic without quote/michael jackson                                                      1.12      4.6±0.02ms        ? ?/sec    1.00      4.1±0.02ms        ? ?/sec
smol-songs.csv: basic without quote/tamo                                                                 1.16  1072.8±11.71µs        ? ?/sec    1.00   927.4±10.85µs        ? ?/sec
smol-songs.csv: basic without quote/thelonious monk                                                      1.10      5.9±0.02ms        ? ?/sec    1.00      5.3±0.06ms        ? ?/sec
smol-songs.csv: big filter/Notstandskomitee                                                              1.03      3.5±0.03ms        ? ?/sec    1.00      3.4±0.02ms        ? ?/sec
smol-songs.csv: big filter/charles                                                                       1.46    464.2±2.57µs        ? ?/sec    1.00    318.6±1.52µs        ? ?/sec
smol-songs.csv: big filter/charles mingus                                                                1.64   1257.3±8.79µs        ? ?/sec    1.00    766.8±4.51µs        ? ?/sec
smol-songs.csv: big filter/david                                                                         1.16   1087.6±9.86µs        ? ?/sec    1.00    937.4±7.77µs        ? ?/sec
smol-songs.csv: big filter/david bowie                                                                   1.27      2.3±0.01ms        ? ?/sec    1.00   1821.5±8.19µs        ? ?/sec
smol-songs.csv: big filter/john                                                                          1.14  1238.0±21.04µs        ? ?/sec    1.00  1089.2±11.10µs        ? ?/sec
smol-songs.csv: big filter/marcus miller                                                                 1.59  1334.0±16.04µs        ? ?/sec    1.00    836.5±4.30µs        ? ?/sec
smol-songs.csv: big filter/michael jackson                                                               1.27      2.3±0.01ms        ? ?/sec    1.00  1795.0±12.29µs        ? ?/sec
smol-songs.csv: big filter/tamo                                                                          1.91    304.8±2.25µs        ? ?/sec    1.00    159.5±1.69µs        ? ?/sec
smol-songs.csv: big filter/thelonious monk                                                               1.11      4.2±0.02ms        ? ?/sec    1.00      3.7±0.02ms        ? ?/sec
smol-songs.csv: desc + default/Notstandskomitee                                                          1.03      3.7±0.02ms        ? ?/sec    1.00      3.6±0.01ms        ? ?/sec
smol-songs.csv: desc + default/charles                                                                   1.08   1882.2±9.71µs        ? ?/sec    1.00  1744.4±14.56µs        ? ?/sec
smol-songs.csv: desc + default/charles mingus                                                            1.18      3.1±0.01ms        ? ?/sec    1.00      2.6±0.01ms        ? ?/sec
smol-songs.csv: desc + default/david                                                                     1.02      6.1±0.02ms        ? ?/sec    1.00      6.0±0.03ms        ? ?/sec
smol-songs.csv: desc + default/david bowie                                                               1.07      9.9±0.04ms        ? ?/sec    1.00      9.3±0.03ms        ? ?/sec
smol-songs.csv: desc + default/john                                                                      1.02      4.9±0.08ms        ? ?/sec    1.00      4.8±0.07ms        ? ?/sec
smol-songs.csv: desc + default/marcus miller                                                             1.11      4.7±0.02ms        ? ?/sec    1.00      4.2±0.02ms        ? ?/sec
smol-songs.csv: desc + default/michael jackson                                                           1.07      7.4±0.03ms        ? ?/sec    1.00      6.9±0.02ms        ? ?/sec
smol-songs.csv: desc + default/tamo                                                                      1.09   1708.4±9.45µs        ? ?/sec    1.00   1574.3±9.82µs        ? ?/sec
smol-songs.csv: desc + default/thelonious monk                                                           1.05      5.6±0.02ms        ? ?/sec    1.00      5.4±0.02ms        ? ?/sec
smol-songs.csv: desc/Notstandskomitee                                                                    1.03      3.3±0.03ms        ? ?/sec    1.00      3.2±0.01ms        ? ?/sec
smol-songs.csv: desc/charles                                                                             1.27    676.9±4.33µs        ? ?/sec    1.00    532.5±3.26µs        ? ?/sec
smol-songs.csv: desc/charles mingus                                                                      1.54   1397.8±8.67µs        ? ?/sec    1.00    905.4±6.42µs        ? ?/sec
smol-songs.csv: desc/david                                                                               1.18    960.7±7.83µs        ? ?/sec    1.00    815.5±3.72µs        ? ?/sec
smol-songs.csv: desc/david bowie                                                                         1.40  1736.7±11.55µs        ? ?/sec    1.00  1243.0±10.59µs        ? ?/sec
smol-songs.csv: desc/john                                                                                1.21    851.0±5.14µs        ? ?/sec    1.00    706.1±3.06µs        ? ?/sec
smol-songs.csv: desc/marcus miller                                                                       1.43   1635.6±6.68µs        ? ?/sec    1.00   1145.1±8.11µs        ? ?/sec
smol-songs.csv: desc/michael jackson                                                                     1.40   1669.3±7.92µs        ? ?/sec    1.00   1192.2±6.99µs        ? ?/sec
smol-songs.csv: desc/tamo                                                                                2.70    227.3±3.44µs        ? ?/sec    1.00     84.3±0.61µs        ? ?/sec
smol-songs.csv: desc/thelonious monk                                                                     1.16      4.1±0.01ms        ? ?/sec    1.00      3.5±0.02ms        ? ?/sec
smol-songs.csv: prefix search/a                                                                          1.12  1372.5±12.54µs        ? ?/sec    1.00  1220.6±17.26µs        ? ?/sec
smol-songs.csv: prefix search/b                                                                          1.13   1235.4±8.87µs        ? ?/sec    1.00  1089.7±10.75µs        ? ?/sec
smol-songs.csv: prefix search/i                                                                          1.11  1506.4±28.31µs        ? ?/sec    1.00  1354.4±17.05µs        ? ?/sec
smol-songs.csv: prefix search/s                                                                          1.18   985.1±15.30µs        ? ?/sec    1.00    833.2±4.68µs        ? ?/sec
smol-songs.csv: prefix search/x                                                                          1.47    429.8±3.09µs        ? ?/sec    1.00    291.8±2.27µs        ? ?/sec
smol-songs.csv: proximity/7000 Danses Un Jour Dans Notre Vie                                             3.65     18.7±0.51ms        ? ?/sec    1.00      5.1±0.86ms        ? ?/sec
smol-songs.csv: proximity/The Disneyland Sing-Along Chorus                                               1.45     12.8±0.08ms        ? ?/sec    1.00      8.8±0.03ms        ? ?/sec
smol-songs.csv: proximity/Under Great Northern Lights                                                    1.60      5.1±0.02ms        ? ?/sec    1.00      3.2±0.02ms        ? ?/sec
smol-songs.csv: proximity/black saint sinner lady                                                        1.46      6.1±0.02ms        ? ?/sec    1.00      4.2±0.02ms        ? ?/sec
smol-songs.csv: proximity/les dangeureuses 1960                                                          1.18      6.0±0.02ms        ? ?/sec    1.00      5.1±0.02ms        ? ?/sec
smol-songs.csv: typo/Arethla Franklin                                                                    1.92    902.0±6.83µs        ? ?/sec    1.00    469.6±2.70µs        ? ?/sec
smol-songs.csv: typo/Disnaylande                                                                         1.02      3.3±0.03ms        ? ?/sec    1.00      3.3±0.02ms        ? ?/sec
smol-songs.csv: typo/dire straights                                                                      1.11      4.2±0.02ms        ? ?/sec    1.00      3.8±0.02ms        ? ?/sec
smol-songs.csv: typo/fear of the duck                                                                    3.05      3.0±0.01ms        ? ?/sec    1.00    974.4±3.72µs        ? ?/sec
smol-songs.csv: typo/indochie                                                                            2.08    272.8±2.08µs        ? ?/sec    1.00    131.2±1.38µs        ? ?/sec
smol-songs.csv: typo/indochien                                                                           1.83    309.6±1.87µs        ? ?/sec    1.00    169.5±1.25µs        ? ?/sec
smol-songs.csv: typo/klub des loopers                                                                    2.62  1622.6±14.43µs        ? ?/sec    1.00    618.3±6.16µs        ? ?/sec
smol-songs.csv: typo/michel depech                                                                       1.81    952.6±4.39µs        ? ?/sec    1.00    525.2±5.01µs        ? ?/sec
smol-songs.csv: typo/mongus                                                                              1.92    303.2±2.28µs        ? ?/sec    1.00    158.1±0.95µs        ? ?/sec
smol-songs.csv: typo/stromal                                                                             1.86    310.4±2.77µs        ? ?/sec    1.00    167.1±1.18µs        ? ?/sec
smol-songs.csv: typo/the white striper                                                                   2.23  1792.6±10.24µs        ? ?/sec    1.00    804.0±3.72µs        ? ?/sec
smol-songs.csv: typo/thelonius monk                                                                      2.22    759.0±6.25µs        ? ?/sec    1.00    342.5±4.84µs        ? ?/sec
smol-songs.csv: words/7000 Danses / Le Baiser / je me trompe de mots                                     4.00     94.5±3.12ms        ? ?/sec    1.00     23.6±3.71ms        ? ?/sec
smol-songs.csv: words/Bring Your Daughter To The Slaughter but now this is not part of the title         3.78    197.4±9.04ms        ? ?/sec    1.00     52.2±6.56ms        ? ?/sec
smol-songs.csv: words/The Disneyland Children's Sing-Alone song                                          2.50     33.6±0.46ms        ? ?/sec    1.00     13.4±0.61ms        ? ?/sec
smol-songs.csv: words/les liaisons dangeureuses 1793                                                     1.62      7.2±0.03ms        ? ?/sec    1.00      4.5±0.04ms        ? ?/sec
smol-songs.csv: words/seven nation mummy                                                                 1.94      2.5±0.01ms        ? ?/sec    1.00  1308.4±16.35µs        ? ?/sec
smol-songs.csv: words/the black saint and the sinner lady and the good doggo                             3.06    202.0±7.10ms        ? ?/sec    1.00     66.0±6.13ms        ? ?/sec
smol-songs.csv: words/whathavenotnsuchforth and a good amount of words to pop to match the first one     3.08    205.4±6.88ms        ? ?/sec    1.00     66.6±5.31ms        ? ?/sec

[Kerollmops]

Thank you very much! Perfs are kind of back!
bors merge

[bors]

Build succeeded:

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• Tests on macos-latest
• Tests on ubuntu-18.04
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