大约有 42,000 项符合查询结果（耗时：0.1066秒） [XML]
How many database indexes is too many?
...
I made some simple tests on my real project and real MySql database. I already answered in this topic: What is the cost of indexing multiple db columns?
But I think it will be better if I quote it here:
I made some simple tests using my real
project and real MySql databa...
How can I combine hashes in Perl?
...y ...)
See also
PM post on merging hashes
PM Categorical Q&A hash union
Perl Cookbook 5.10. Merging Hashes
websearch://perlfaq "merge two hashes"
websearch://perl merge hash
https://metacpan.org/pod/Hash::Merge
Footnotes
1 * (aka associative-array, aka dictionary)
...
in_array multiple values
... developer, you should probably start learning set operations (difference, union, intersection). You can imagine your array as one "set", and the keys you are searching for the other.
Check if ALL needles exist
function in_array_all($needles, $haystack) {
return empty(array_diff($needles, $hays...
Copy table without copying data
...her processes. Basically caused a massive lock meltdown and had to restart MySQL.
– Mark B
Jul 29 '14 at 15:57
6
...
How to make a programme continue to run after log out from ssh? [duplicate]
I have a program that takes a lot of time to finish.
It is running as root over ssh.
I want it to continue to run after I logout,is this possible and how would I achieve this?
...
How do I use su to execute the rest of the bash script as that user?
...Jadhav, he used it here just to show the ID of the current user, the ID of root is 0, so the first id will show you some number, but the second one will definetly show 0 (because the second one was executed inside a block run by root). You can user whoami instead of id which will return the name ins...
How to log something in Rails in an independent log file?
...ActiveRecord::Base
def my_logger
@@my_logger ||= Logger.new("#{Rails.root}/log/my.log")
end
def before_save
my_logger.info("Creating user with name #{self.name}")
end
end
Here I used a class attribute to memoize the logger. This way it won't be created for every single User object...
android: move a view on touch move (ACTION_MOVE)
...nds Activity implements View.OnTouchListener {
TextView _view;
ViewGroup _root;
private int _xDelta;
private int _yDelta;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
_root = (ViewGroup)findViewById(R.id...
Windows 7, 64 bit, DLL problems
...lls other DLL files.
In my case, it was not three .ocx files, but missing MySQL connector DLL file. After installing of MySQL Connector for .NET on server, the problem disappeared.
So, in short, the solution is: check if all your project references are there.
...
How to store date/time and timestamps in UTC time zone with JPA and Hibernate
...
@VladMihalcea if it's for Mysql, one need to tell MySql to use timezone by using useTimezone=true in the connection string. Then only setting property hibernate.jdbc.time_zone will work
– TheCoder
Oct 13 '18 at 1...