jcoglan edited a comment on issue #3773:
URL: https://github.com/apache/couchdb/issues/3773#issuecomment-937846761
It's also interesting that querying the view without `keys` lists two rows
with `q=2`:
```
See what is in the view
00000000 7b 22 72 6f 77 73 22 3a 5b 0d 0a 7b 22 6b 65 79
|{"rows":[..{"key|
00000010 22 3a 5b 22 66 69 6c 65 22 2c 22 63 68 61 c3 ae
|":["file","cha..|
00000020 6e 65 22 5d 2c 22 76 61 6c 75 65 22 3a 31 7d 2c
|ne"],"value":1},|
00000030 0d 0a 7b 22 6b 65 79 22 3a 5b 22 66 69 6c 65 22
|..{"key":["file"|
00000040 2c 22 63 68 61 69 cc 82 6e 65 22 5d 2c 22 76 61
|,"chai..ne"],"va|
00000050 6c 75 65 22 3a 31 7d 0d 0a 5d 7d 0a |lue":1}..]}.|
0000005c
```
... but only a single row with `q=1`. The row returned has key bytes `c3 ae`
representing codepoint U+00EE. Notes its `value` is `2` indicating there are
actually two rows stored in the view, but their keys have been considered equal
by the `_count` function.
```
See what is in the view
00000000 7b 22 72 6f 77 73 22 3a 5b 0d 0a 7b 22 6b 65 79
|{"rows":[..{"key|
00000010 22 3a 5b 22 66 69 6c 65 22 2c 22 63 68 61 c3 ae
|":["file","cha..|
00000020 6e 65 22 5d 2c 22 76 61 6c 75 65 22 3a 32 7d 0d
|ne"],"value":2}.|
00000030 0a 5d 7d 0a |.]}.|
00000034
```
So it does seem as though if these two rows are stored in the same shard,
their keys are considered equal and they get merged, but not if they're
(potentially) stored in different shards. I also tried running this example
with the `reduce` and `group` operations removed just to see what rows we'd
get. With `q=1` or `q=2` I get the same results; all queries return _two_ rows:
```
See what is in the view
00000000 7b 22 74 6f 74 61 6c 5f 72 6f 77 73 22 3a 32 2c
|{"total_rows":2,|
00000010 22 6f 66 66 73 65 74 22 3a 30 2c 22 72 6f 77 73
|"offset":0,"rows|
00000020 22 3a 5b 0d 0a 7b 22 69 64 22 3a 22 64 6f 63 31
|":[..{"id":"doc1|
00000030 22 2c 22 6b 65 79 22 3a 5b 22 66 69 6c 65 22 2c
|","key":["file",|
00000040 22 63 68 61 c3 ae 6e 65 22 5d 2c 22 76 61 6c 75
|"cha..ne"],"valu|
00000050 65 22 3a 6e 75 6c 6c 7d 2c 0d 0a 7b 22 69 64 22
|e":null},..{"id"|
00000060 3a 22 64 6f 63 32 22 2c 22 6b 65 79 22 3a 5b 22
|:"doc2","key":["|
00000070 66 69 6c 65 22 2c 22 63 68 61 69 cc 82 6e 65 22
|file","chai..ne"|
00000080 5d 2c 22 76 61 6c 75 65 22 3a 6e 75 6c 6c 7d 0d
|],"value":null}.|
00000090 0a 5d 7d 0a |.]}.|
00000094
Request the view, one time for each encoding
00000000 7b 22 74 6f 74 61 6c 5f 72 6f 77 73 22 3a 32 2c
|{"total_rows":2,|
00000010 22 6f 66 66 73 65 74 22 3a 30 2c 22 72 6f 77 73
|"offset":0,"rows|
00000020 22 3a 5b 0d 0a 7b 22 69 64 22 3a 22 64 6f 63 31
|":[..{"id":"doc1|
00000030 22 2c 22 6b 65 79 22 3a 5b 22 66 69 6c 65 22 2c
|","key":["file",|
00000040 22 63 68 61 c3 ae 6e 65 22 5d 2c 22 76 61 6c 75
|"cha..ne"],"valu|
00000050 65 22 3a 6e 75 6c 6c 7d 2c 0d 0a 7b 22 69 64 22
|e":null},..{"id"|
00000060 3a 22 64 6f 63 32 22 2c 22 6b 65 79 22 3a 5b 22
|:"doc2","key":["|
00000070 66 69 6c 65 22 2c 22 63 68 61 69 cc 82 6e 65 22
|file","chai..ne"|
00000080 5d 2c 22 76 61 6c 75 65 22 3a 6e 75 6c 6c 7d 0d
|],"value":null}.|
00000090 0a 5d 7d 0a |.]}.|
00000094
00000000 7b 22 74 6f 74 61 6c 5f 72 6f 77 73 22 3a 32 2c
|{"total_rows":2,|
00000010 22 6f 66 66 73 65 74 22 3a 30 2c 22 72 6f 77 73
|"offset":0,"rows|
00000020 22 3a 5b 0d 0a 7b 22 69 64 22 3a 22 64 6f 63 31
|":[..{"id":"doc1|
00000030 22 2c 22 6b 65 79 22 3a 5b 22 66 69 6c 65 22 2c
|","key":["file",|
00000040 22 63 68 61 c3 ae 6e 65 22 5d 2c 22 76 61 6c 75
|"cha..ne"],"valu|
00000050 65 22 3a 6e 75 6c 6c 7d 2c 0d 0a 7b 22 69 64 22
|e":null},..{"id"|
00000060 3a 22 64 6f 63 32 22 2c 22 6b 65 79 22 3a 5b 22
|:"doc2","key":["|
00000070 66 69 6c 65 22 2c 22 63 68 61 69 cc 82 6e 65 22
|file","chai..ne"|
00000080 5d 2c 22 76 61 6c 75 65 22 3a 6e 75 6c 6c 7d 0d
|],"value":null}.|
00000090 0a 5d 7d 0a |.]}.|
00000094
```
Something curious is going on here: both documents are stored distinctly and
produce two distinct view rows, the `keys` param matches both rows no matter
which encoding is used, and when `q=1` the `reduce`/`group` operation with
`_count` considers the rows' keys equal and merges them.
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