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Why does PostgreSQL perform sequential scan on indexed column?
...ster than an index scan.
This is because an index scan requires several IO operations for each row (look up the row in the index, then retrieve the row from the heap). Whereas a sequential scan only requires a single IO for each row - or even less because a block (page) on the disk contains more...
What is the difference between user and kernel modes in operating systems?
...cted
access to the underlying hardware. It
can execute any CPU instruction and
reference any memory address. Kernel
mode is generally reserved for the
lowest-level, most trusted functions
of the operating system. Crashes in
kernel mode are catastrophic; they
will halt the entire PC.
...
How to check if a file exists in a folder?
... Noe that this answer returns false if the user does not have permission to read the file. So it does more than just checkinf if the file exists in a folder. You might want to use DirectoryInfo.GetFiles() and enumerate the result.
– ogborstad
Feb 10 '15 a...
Xcode 4 and Core Data: How to enable SQL Debugging
I'm working on a universal iOS app and I'd like to see the raw SQL in the logs when I'm debugging. There is some info in this blog post about how to enable raw SQL logging for iOS Core Data development. The given example is for Xcode 3 and it's just not clear to me how to enable this in Xcode 4.
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Can I mix Swift with C++? Like the Objective-C .mm files
...en try to compile that as Objective-C++.
Swift doesn't have the same relationship. It is not a superset of C or C++, and you can't directly use either in a .swift file.
"Using Swift with Cocoa and Objective-C" also tells us:
You cannot import C++ code directly into Swift. Instead, create an Ob...
How to make an HTTP POST web request
...d approach, and is asynchronous and high performance. Use the built-in version in most cases, but for very old platforms there is a NuGet package.
using System.Net.Http;
Setup
It is recommended to instantiate one HttpClient for your application's lifetime and share it unless you have a specific ...
String isNullOrEmpty in Java? [duplicate]
...
I was confused between the distinction between blank and empty, so I looked it up; blank means, "", null, and any amount of whitespace; empty is just "" and null.
– James McMahon
Feb 16 '10 at 15:50
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How to get device make and model on iOS?
...
EITHER try this library: http://github.com/erica/uidevice-extension/ (by Erica Sadun). (The library is 7-8 years old, and hence is obsolete)
(Sample Code):
[[UIDevice currentDevice] platformType] // ex: UIDevice4GiPhone
[[UIDevice currentDevice] platformString] // ex: @"iPhone...
Read whole ASCII file into C++ std::string [duplicate]
...
Update: Turns out that this method, while following STL idioms well, is actually surprisingly inefficient! Don't do this with large files. (See: http://insanecoding.blogspot.com/2011/11/how-to-read-in-file-in-c.html)
You can make a streambuf iterator out of the file and initialize ...
Idiomatic way to convert an InputStream to a String in Scala
I have a handy function that I've used in Java for converting an InputStream to a String. Here is a direct translation to Scala:
...