Stop reindexing already indexed documents

[irevoire]

 % ./compare.sh indexing_stop-reindexing-unchanged-documents_cb5a1669.json indexing_main_eeba1960.json
group                                                                     indexing_main_eeba1960                 indexing_stop-reindexing-unchanged-documents_cb5a1669
-----                                                                     ----------------------                 -----------------------------------------------------
indexing/-geo-delete-facetedNumber-facetedGeo-searchable-                 1.03      2.0±0.22ms        ? ?/sec    1.00  1955.4±336.24µs        ? ?/sec
indexing/-movies-delete-facetedString-facetedNumber-searchable-           1.08     11.0±2.93ms        ? ?/sec    1.00     10.2±4.04ms        ? ?/sec
indexing/-movies-delete-facetedString-facetedNumber-searchable-nested-    1.00     15.1±3.89ms        ? ?/sec    1.14     17.1±5.18ms        ? ?/sec
indexing/-songs-delete-facetedString-facetedNumber-searchable-            1.26    59.2±12.01ms        ? ?/sec    1.00     47.1±8.52ms        ? ?/sec
indexing/-wiki-delete-searchable-                                         1.08   316.6±31.53ms        ? ?/sec    1.00   293.6±17.00ms        ? ?/sec
indexing/Indexing geo_point                                               1.01      60.9±0.31s        ? ?/sec    1.00      60.6±0.36s        ? ?/sec
indexing/Indexing movies in three batches                                 1.04      20.0±0.30s        ? ?/sec    1.00      19.2±0.25s        ? ?/sec
indexing/Indexing movies with default settings                            1.02      19.1±0.18s        ? ?/sec    1.00      18.7±0.24s        ? ?/sec
indexing/Indexing nested movies with default settings                     1.02      26.2±0.29s        ? ?/sec    1.00      25.9±0.22s        ? ?/sec
indexing/Indexing nested movies without any facets                        1.02      25.3±0.32s        ? ?/sec    1.00      24.7±0.26s        ? ?/sec
indexing/Indexing songs in three batches with default settings            1.00      66.7±0.41s        ? ?/sec    1.01      67.1±0.86s        ? ?/sec
indexing/Indexing songs with default settings                             1.00      58.3±0.90s        ? ?/sec    1.01      58.8±1.32s        ? ?/sec
indexing/Indexing songs without any facets                                1.00      54.5±1.43s        ? ?/sec    1.01      55.2±1.29s        ? ?/sec
indexing/Indexing songs without faceted numbers                           1.00      57.9±1.20s        ? ?/sec    1.01      58.4±0.93s        ? ?/sec
indexing/Indexing wiki                                                    1.00   1052.0±10.95s        ? ?/sec    1.02   1069.4±20.38s        ? ?/sec
indexing/Indexing wiki in three batches                                   1.00    1193.1±8.83s        ? ?/sec    1.00    1189.5±9.40s        ? ?/sec
indexing/Reindexing geo_point                                             3.22      67.5±0.73s        ? ?/sec    1.00      21.0±0.16s        ? ?/sec
indexing/Reindexing movies with default settings                          3.75      19.4±0.28s        ? ?/sec    1.00       5.2±0.05s        ? ?/sec
indexing/Reindexing songs with default settings                           8.90      61.4±0.91s        ? ?/sec    1.00       6.9±0.07s        ? ?/sec
indexing/Reindexing wiki                                                  1.00   1748.2±35.68s        ? ?/sec    1.00   1750.5±18.53s        ? ?/sec

tldr: We do not lose any performance on the normal indexing benchmark, but we get between 3 and 8 times faster on the reindexing benchmarks 👍

[ManyTheFish]

Seems good to me

[Kerollmops]

Looks good to me but please, I don't want to rebase #561 again... 😭

[curquiza]

We need to fix the git conflicts before merging 😊

[irevoire]

I rebased on main

[ManyTheFish]

Bors merge

[bors]

Build succeeded:

• Run Rustfmt
• Tests on macos-latest
• Tests on ubuntu-18.04
• Tests on windows-latest