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Include all existing fields and add new fields to document
...s the new fields.
db.collection.aggregate([
{ "$addFields": { "custom_field": "$obj.obj_field1" } }
])
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将Linux代码移植到Windows的简单方法 - 操作系统(内核) - 清泛网 - 专注C/C++及内核技术
...（Header File）的包含问题。在Config.h中定义了很多类似HAVE_XXXX_H。比如定义HAVE_CONFIG_H为1表示工程中可以使用config.h。
#define HAVE_MALLOC_H 1表示可以在工程中使用Malloc.h头文件。通过调整这些定义值，可以去除一些Windows平台下面没有...
Sending HTTP POST Request In Java
...alue(), "UTF-8"));
byte[] out = sj.toString().getBytes(StandardCharsets.UTF_8);
int length = out.length;
We can then attach our form contents to the http request with proper headers and send it.
http.setFixedLengthStreamingMode(length);
http.setRequestProperty("Content-Type", "application/x-www-f...
Is it expensive to use try-catch blocks even if an exception is never thrown?
...
public class TryFinally {
public TryFinally();
Code:
0: aload_0
1: invokespecial #1 // Method java/lang/Object."<init>":()V
4: return
public static void main(java.lang.String[]) throws java.lang.Throwable;
Code:
0: new #2 ...
Remove blank attributes from an Object in Javascript
...a simple solution:
var obj = {name: 'John', age: null};
var compacted = _.pickBy(obj);
This will only work with lodash 4, pre lodash 4 or underscore.js, use _.pick(obj, _.identity);
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How to avoid isset() and empty()
...of "xyz is undefined" and "undefined offset" messages when running on the E_NOTICE error level, because the existence of variables is not explicitly checked using isset() and consorts.
...
Why use prefixes on member variables in C++ classes
...ng underscore before a capital letter in a word is reserved.
For example:
_Foo
_L
are all reserved words while
_foo
_l
are not. There are other situations where leading underscores before lowercase letters are not allowed. In my specific case, I found the _L happened to be reserved by Visual...
Getting the last argument passed to a shell script
...
The simplest answer for bash 3.0 or greater is
_last=${!#} # *indirect reference* to the $# variable
# or
_last=$BASH_ARGV # official built-in (but takes more typing :)
That's it.
$ cat lastarg
#!/bin/bash
# echo the last arg given:
_last=${!#}
echo $_last
_last...
How to set a value of a variable inside a template code?
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If you need to declare a list, use make_list. docs.djangoproject.com/en/1.9/ref/templates/builtins/#make-list
– MrValdez
Jul 1 '16 at 7:55
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Which is faster : if (bool) or if(int)?
...
Does this also apply to 64-bit processes, that __int64 is faster than int? Or CPU deals 32-bit integer with 32-bit instruction sets separately?
– Crend King
Apr 27 '11 at 21:22
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