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Transaction isolation levels relation with locks on table
...implementation and the algorithm they use: MVCC or Two Phase Locking.
CUBRID (open source RDBMS) explains the idea of this two algorithms:
Two-phase locking (2PL)
The first one is when the T2 transaction tries to change the A record,
it knows that the T1 transaction has already cha...
Which kind of pointer do I use when?
...e rage. I never really looked into the other smart pointer types boost provided. I understand that C++11 now provides some of the types boost came up with, but not all of them.
...
What is the purpose of setting a key in data.table?
...two things:
reorders the rows of the data.table DT by the column(s) provided (a, b) by reference, always in increasing order.
marks those columns as key columns by setting an attribute called sorted to DT.
The reordering is both fast (due to data.table's internal radix sorting) and memory effic...
How do CDI and EJB compare? interact?
...llows you to inject implementation into your service or whatever. The main idea is that class, where you inject, should be managed by EJB container.
Seems that CDI does understand what EJB is, so in Java EE 6 compliant server, in your servlet you can write both
@EJB EJBService ejbService;
and
@Inje...
Why should we NOT use sys.setdefaultencoding(“utf-8”) in a py script?
... time, when Python scans the environment. It has to be called in a system-wide module, sitecustomize.py, After this module has been evaluated, the setdefaultencoding() function is removed from the sys module.
The only way to actually use it is with a reload hack that brings the attribute back.
A...
Why does X[Y] join of data.tables not allow a full outer join, or a left join?
...ifferent so change to be the same as `merge`
setcolorder(le, names(mallx))
identical(le, mallx)
# [1] TRUE
If you want a full outer join
# the unique values for the keys over both data sets
unique_keys <- unique(c(X[,t], Y[,t]))
Y[X[J(unique_keys)]]
## t b a
## 1: 1 NA 1
## 2: 2 NA 4
## ...
What's the difference between “groups” and “captures” in .NET regular expressions?
... a "capture" are when it comes to .NET's regular expression language. Consider the following C# code:
5 Answers
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What is the best way to stop people hacking the PHP-based highscore table of a Flash game
...m with Internet games and contests. Your Flash code works with users to decide a score for a game. But users aren't trusted, and the Flash code runs on the user's computer. You're SOL. There is nothing you can do to prevent an attacker from forging high scores:
Flash is even easier to reverse engi...
What does “dereferencing” a pointer mean?
...t's (current) value - I focus below on C and C++.
A pointer scenario
Consider in C, given a pointer such as p below...
const char* p = "abc";
...four bytes with the numerical values used to encode the letters 'a', 'b', 'c', and a 0 byte to denote the end of the textual data, are stored somewher...
Why do we copy then move?
I saw code somewhere in which someone decided to copy an object and subsequently move it to a data member of a class. This left me in confusion in that I thought the whole point of moving was to avoid copying. Here is the example:
...