大约有 6,886 项符合查询结果（耗时：0.0285秒） [XML]
How big is too big for a PostgreSQL table?
...u are doing.
Depending on your data distribution you can use a mixture of indexes, filtered indexes, and table partitioning of some kind to speed thing up once you see what performance issues you may or may not have. Your problem will be the same on any other RDMS that I know of. If you only need ...
Generating all permutations of a given string
... {
res.add(s);
} else if (s.length() > 1) {
int lastIndex = s.length() - 1;
// Find out the last character
String last = s.substring(lastIndex);
// Rest of the string
String rest = s.substring(0, lastIndex);
// Perform permutation on the...
How can I convert a hex string to a byte array? [duplicate]
...g));
}
byte[] data = new byte[hexString.Length / 2];
for (int index = 0; index < data.Length; index++)
{
string byteValue = hexString.Substring(index * 2, 2);
data[index] = byte.Parse(byteValue, NumberStyles.HexNumber, CultureInfo.InvariantCulture);
}
ret...
how to get the one entry from hashmap without iterating
...no such thing as 'the first entry', and that's also why there is no get-by-index method on Map (or HashMap).
You could do this:
Map<String, String> map = ...; // wherever you get this from
// Get the first entry that the iterator returns
Map.Entry<String, String> entry = map.entrySet...
How fast is D compared to C++?
...ting average
Removed the size_type and replaced appropriately with the new index_type alias
...thus resulting in scalar2.cpp (pastebin):
import std.stdio : writeln;
import std.datetime : Clock, Duration;
import std.array : uninitializedArray;
import std.random : uniform;
alia...
How do I toggle an element's class in pure JavaScript?
...Name){
return;
}
var classString = element.className, nameIndex = classString.indexOf(className);
if (nameIndex == -1) {
classString += ' ' + className;
}
else {
classString = classString.substr(0, nameIndex) + classString.substr(nameIndex+className.lengt...
How to Get True Size of MySQL Database?
... MySQL forum:
SELECT table_schema "database name",
sum( data_length + index_length ) / 1024 / 1024 "database size in MB",
sum( data_free )/ 1024 / 1024 "free space in MB"
FROM information_schema.TABLES
GROUP BY table_schema;
Or in a single line for easier copy-pasting:
SELECT table_sche...
PhoneGap: Detect if running on desktop browser
...n a browser or not, here is another great option:
var app = document.URL.indexOf( 'http://' ) === -1 && document.URL.indexOf( 'https://' ) === -1;
if ( app ) {
// PhoneGap application
} else {
// Web page
}
as seen here: Detect between a mobile browser or a PhoneGap application...
Should each and every table have a primary key?
...s, most RDBMS engines will benefit from including these fields in a unique index.
And since any primary key involves creating a unique index, you should declare it and get both logical consistency and performance.
See this article in my blog for why you should always create a unique index on uniqu...
Creating a zero-filled pandas data frame
...
You can try this:
d = pd.DataFrame(0, index=np.arange(len(data)), columns=feature_list)
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