error in string sorting

[hereisok]

hi, The couchdb version I use is 3.1.0.

Below is my document in the database,

_id	group_id	msg_id
H-jqPgaMjkaqpmZsyX97_uMOtD3rsYPcABjz8=	lEJXOvV-jqPgaMjkaqpmZsyX97_uMOtD3rsYPcABjz8=	H
h-jqPgaMjkaqpmZsyX97_uMOtD3rsYPcABjz8=	lEJXOvV-jqPgaMjkaqpmZsyX97_uMOtD3rsYPcABjz8=	h
b-lEJXOvV-jqPgaMjkaqpmZsyX97_uMOtD3rsYPcABjz8=	lEJXOvV-jqPgaMjkaqpmZsyX97_uMOtD3rsYPcABjz8=	b
A-lEJXOvV-jqPgaMjkaqpmZsyX97_uMOtD3rsYPcABjz8=	lEJXOvV-jqPgaMjkaqpmZsyX97_uMOtD3rsYPcABjz8=	A
a-lEJXOvV-jqPgaMjkaqpmZsyX97_uMOtD3rsYPcABjz8=	lEJXOvV-jqPgaMjkaqpmZsyX97_uMOtD3rsYPcABjz8=	a
7ewRhpLu5-567jqPgaMjkaqpmZsyX97_uMOtD3rsYPcABjz8=	lEJXOvV-jqPgaMjkaqpmZsyX97_uMOtD3rsYPcABjz8=	7ewRhpLu5
7ewRHPJZN-567jqPgaMjkaqpmZsyX97_uMOtD3rsYPcABjz8=	lEJXOvV-jqPgaMjkaqpmZsyX97_uMOtD3rsYPcABjz8=	7ewRHPJZN

I created an index:

{
        "index": {
            "fields": ["group_id", "msg_id"]
        },
        "name": "msg-id-index",
        "type": "json",
        "ddoc": "_design/index_msg-id-index"
}

Then sort query based on msg_id. Below is the result of my query.

According to couchdb's documentation, I know that the order of "H" is higher than "h", but why is the order of "7ewRhpLu5" higher than "7ewRHPJZN"?

[hereisok]

apache/couchdb#3048