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Is there a good reason I see VARCHAR(255) used so often (as opposed to another length)?
...egers, you count starting from 0 and you end at 255. But with places in a string, you count starting from the 1st place, so doesn't it make sense to end at the 256th place, because you started at 1 instead of 0? I'm not agreeing with varchar(256) entirely just yet, because of string_length() resul...
Optimising Android application before release [closed]
...g
recycle complex java objects such as XmlPullParserFactory/BitmapFactory/StringBuilder/Matcher etc.
For more battery tricks see Coding for Life - Battery Life, That Is.
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How to print color in console using System.out.println?
...you could define constants like these for the colors:
public static final String ANSI_RESET = "\u001B[0m";
public static final String ANSI_BLACK = "\u001B[30m";
public static final String ANSI_RED = "\u001B[31m";
public static final String ANSI_GREEN = "\u001B[32m";
public static final String ANSI_...
Why unsigned integer is not available in PostgreSQL?
...rser to deal with literals because PgSQL has such an easy way to interpret strings as literals, just write '4294966272'::uint4 as your literals. Casts shouldn't be a huge deal either. You don't even need to do range exceptions, you can just treat the semantics of '4294966273'::uint4::int as -1024. O...
Can hash tables really be O(1)?
...ll as the above, if you are using immutable objects as your keys e.g. Java Strings, having calculated the hash once, you can remember it and not have to calculate it again. On the other hand, you can't usually rely on the hash to tell if two keys are equal once you have found the right bucket, so f...
What is the proper way to format a multi-line dict in Python?
...(4, 'd'),
],
}
Similarly, here's my preferred way of including large strings without introducing any whitespace (like you'd get if you used triple-quoted multi-line strings):
data = (
"iVBORw0KGgoAAAANSUhEUgAAABAAAAAQCAYAAAAf8/9hAAAABG"
"l0RVh0U29mdHdhcmUAQWRvYmUgSW1hZ2VSZWFkeXHJZTwAA...
C/C++ Struct vs Class
... examples given:
struct Pair { // the members can vary independently
string name;
int volume;
};
// but
class Date {
public:
// validate that {yy, mm, dd} is a valid date and initialize
Date(int yy, Month mm, char dd);
// ...
private:
int y;
Month m;
char d; //...
Removing all non-numeric characters from string in Python
How do we remove all non-numeric characters from a string in Python?
7 Answers
7
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how to exclude null values in array_agg like in string_agg using postgres?
...s g
GROUP BY g.id
) s
Or, simpler and may be cheaper, using array_to_string which eliminates nulls:
SELECT
g.id,
array_to_string(
array_agg(CASE WHEN g.canonical = 'Y' THEN g.users ELSE NULL END)
, ','
) canonical_users,
array_to_string(
array_agg(CASE ...
Regular expression to match any character being repeated more than 10 times
...ckslashes, e.g. Emacs would make you write \(.\)\1\{9,\} here.
If a whole string should consist of 9 or more identical characters, add anchors around the pattern:
my $regex = qr/^(.)\1{9,}$/;
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