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The following shows how dropping the admin db may leave UUIDs.
test> db.adminCommand({getParameter: 1, featureCompatibilityVersion: 1})
{ "featureCompatibilityVersion" : { "version" : "3.6" }, "ok" : 1 }
test> use local
switched to db local
local> db.runCommand({listCollections: 1})
{
"cursor" : {
"id" : NumberLong(0),
"ns" : "local.$cmd.listCollections",
"firstBatch" : [
{
"name" : "startup_log",
"type" : "collection",
"options" : {
"capped" : true,
"size" : 10485760
},
"info" : {
"readOnly" : false,
"uuid" : BinData(4,"8Vlh0RQDSSy2HRFJJlBVDQ==")
},
"idIndex" : {
"v" : 2,
"key" : {
"_id" : 1
},
"name" : "_id_",
"ns" : "local.startup_log"
}
}
]
},
"ok" : 1
}
local> use admin
switched to db admin
admin> db.dropDatabase()
{ "dropped" : "admin", "ok" : 1 }
admin> db.adminCommand({getParameter: 1, featureCompatibilityVersion: 1})
{ "featureCompatibilityVersion" : { "version" : "3.4" }, "ok" : 1 }
admin> use local
switched to db local
local> db.runCommand({listCollections: 1})
{
"cursor" : {
"id" : NumberLong(0),
"ns" : "local.$cmd.listCollections",
"firstBatch" : [
{
"name" : "startup_log",
"type" : "collection",
"options" : {
"capped" : true,
"size" : 10485760
},
"info" : {
"readOnly" : false,
"uuid" : BinData(4,"8Vlh0RQDSSy2HRFJJlBVDQ==")
},
"idIndex" : {
"v" : 2,
"key" : {
"_id" : 1
},
"name" : "_id_",
"ns" : "local.startup_log"
}
}
]
},
"ok" : 1
}
local> db.adminCommand({getParameter: 1, featureCompatibilityVersion: 1})
{ "featureCompatibilityVersion" : { "version" : "3.4" }, "ok" : 1 }
local> db.version()
As shown, info.uuid is still present in the local.startup_log collection.
Bug
Major - P3
SERVER-33014 Ensure theoretically unreachable featureCompatibilityVersion document op observers are never reached
SERVER-32126 validate() should do basic sanity checks for UUIDs