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Computed / calculated / virtual / derived columns in PostgreSQL
...al, but makes makes life a bit easier).
Suppose my computation is md5(some_string_field), then I create the index as:
CREATE INDEX some_string_field_md5_index ON some_table(MD5(some_string_field));
Now, any queries that act on MD5(some_string_field) will use the index rather than computing it f...
Generate full SQL script from EF 5 Code First Migrations
...ate a database to a specific version.
Script-Migration -From 20190101011200_Initial-Migration -To 20190101021200_Migration-2
https://docs.microsoft.com/en-us/ef/core/managing-schemas/migrations/#generate-sql-scripts
There are several options to this command.
The from migration should be the last m...
sed one-liner to convert all uppercase to lowercase?
...amel case example. 's/\w+/\u&/g' also works.
– PJ_Finnegan
Feb 26 '15 at 23:36
1
...
How to convert a byte array to a hex string in Java?
...swer, this is the function I currently use:
private static final char[] HEX_ARRAY = "0123456789ABCDEF".toCharArray();
public static String bytesToHex(byte[] bytes) {
char[] hexChars = new char[bytes.length * 2];
for (int j = 0; j < bytes.length; j++) {
int v = bytes[j] & 0xFF;...
Custom HTTP headers : naming conventions
...onvention for these that people tend to use? (such as prefixing them with "_" perhaps? ie: ("_ClientDataFoo")
– Marchy
Feb 9 '14 at 17:25
...
iOS 5 Best Practice (Release/retain?)
...time compatibility glue code to your app. This works for everything except __weak variables, which require more support than the compatibility code can provide. ARC on iOS 4 is simpler than non-ARC code, but it's not as simple as ARC on iOS 5." By the way, the WWDC schedule app was written with AR...
How can I efficiently select a Standard Library container in C++11?
...ecause list is not such a good container in general, and neither is forward_list. Both lists are very specialized containers for niche applications.
To build such a chart, you just need two simple guidelines:
Choose for semantics first
When several choices are available, go for the simplest
Wor...
Entity Framework: There is already an open DataReader associated with this Command
...ng to iterate is kind of lazy loading (IQueriable).
foreach (var user in _dbContext.Users)
{
}
Converting the IQueriable collection into other enumerable collection will solve this problem.
example
_dbContext.Users.ToList()
Note: .ToList() creates a new set every-time and it can cause th...
Is there a way to iterate over a dictionary?
...alue] = value;
}
... summing up the numbers with the block approach ...
__block int sum = 0;
[dict enumerateKeysAndObjectsUsingBlock:^(NSString* key, NSNumber* value, BOOL* stop) {
sum += value.intValue;
}];
... rather than the loop approach ...
int sum = 0;
for (NSString* key in dict)
sum...
How to save an image to localStorage and display it on the next page?
..."text"/>
Then get the dimensions of your file into the input boxes
var _URL = window.URL || window.webkitURL;
$("#file-input").change(function(e) {
var file, img;
if ((file = this.files[0])) {
img = new Image();
img.onload = function() {
$("#file-h").val(this....