大约有 40,000 项符合查询结果（耗时：0.0748秒） [XML]
E11000 duplicate key error index in mongodb mongoose
... null value.
In other words, a sparse index is ok with multiple documents all having null values.
sparse indexes
From comments:
Your error says that the key is named mydb.users.$email_1 which makes me suspect that you have an index on both users.email and users.local.email (The former being old an...
Remove Object from Array using JavaScript
...
This however will remove all the occurrences found, not only the first one
– Flavien Volken
Jul 12 '16 at 6:49
6
...
How to style a div to be a responsive square? [duplicate]
...
Very nice but browser support is a little bit sketchy at the moment though isn't it - google.ie/…
– byronyasgur
Dec 4 '13 at 18:25
3
...
dplyr: “Error in n(): function should not be called directly”
...ction" specification, like example below:
delay <- dplyr::summarise(by_tailnum,
count = n(),
dist = mean(distance, na.rm = TRUE),
delay = mean(arr_delay, na.rm = TRUE))
share
|
improv...
Mapping a function on the values of a map in Clojure
...ure.walk/walk #(apply f %) identity m) )
Parellel versions – pmap-map, etc.
There are also parallel versions of these functions if you need them. They simply use pmap instead of map.
(defn pmap-map [f m]
(into (empty m) (pmap #(apply f %) m)) )
(defn pmap-map-keys [f m]
(pmap-map (fn [...
Are there any CSV readers/writer libraries in C#? [closed]
...m just looking for a way to prevent errors in the files (escaping properly etc).
– u84six
Oct 9 '18 at 21:09
Yes. You ...
How do you create a Swift Date object?
... dateFromString. If you wanted to return a nil on bad parses, you would ideally use a failible initializer; but you cannot do that now (June 2015), because of a limitation in Swift 1.2, so then you're next best choice is to use a class factory method.
A more elaborate example, which addresses both ...
Ignore mapping one property with Automapper
...nore(record => record.AnotherField)
.Ignore(record => record.Etc);
You could also rewrite it to work with params, but I don't like the look of a method with loads of lambdas.
share
|
...
Firefox 'Cross-Origin Request Blocked' despite headers
... folder .htaccess).
I added a lot of console.log("Hi FF, you are here A") etc to see what was going on.
At first it looked like it hanged on xhr.send(). But then I discovered it did not get to the this statement. I placed another console.log right before it and did not get there - even though the...
Postgres: SQL to list table foreign keys
...raints are the same. The only option is going for pg_constraints, pg_class etc. using oids to join. Postgres' ANSI catalog is only there for compliance but it's flawed. pg_catalog is the way to go. The correct answer is here dba.stackexchange.com/questions/36979/retrieving-all-pk-and-fk
...