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When should I use the HashSet type?
...here's no such thing as the 45th element of a set. Items in a set have no ordering. The sets {1, 2, 3} and {2, 3, 1} are identical in every respect because they have the same membership, and membership is all that matters.
It's somewhat dangerous to iterate over a HashSet<T> because doing...
Best way to select random rows PostgreSQL
... select * from table where random() < 0.01;
EXPLAIN select * from table order by random() limit 1000;
A quick test on a large table1 shows, that the ORDER BY first sorts the complete table and then picks the first 1000 items. Sorting a large table not only reads that table but also involves rea...
How to save MySQL query output to excel or .txt file? [duplicate]
...ion which
accepts data in CSV format.
Given a query such as
SELECT order_id,product_name,qty FROM orders
which returns three columns of data, the results can be placed into
the file /tmp/orders.txt using the query:
SELECT order_id,product_name,qty FROM orders
INTO OUTFILE '/tmp/orde...
How to order events bound with jQuery
...eralize this kind of process, but in my case I was only concerned with the order of first event listener in the chain.
If it's of any use, here is my jQuery plugin that binds an event listener that is always triggered before any others:
** UPDATED inline with jQuery changes (thanks Toskan) **
(f...
PostgreSQL - fetch the row which has the Max value for a column
...lue(trans_id) OVER wnd
FROM lives
WINDOW wnd AS (
PARTITION BY usr_id ORDER BY time_stamp, trans_id
ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING
);
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...
Plot correlation matrix into a graph
..., addcolorlabel="no")
corrplot(M, method="number")
corrplot(M)
corrplot(M, order ="AOE")
corrplot(M, order ="AOE", addCoef.col="grey")
corrplot(M, order="AOE", col=col1(20), cl.length=21,addCoef.col="grey")
corrplot(M, order="AOE", col=col1(10),addCoef.col="grey")
corrplot(M, order="AOE", col=col2...
When to use volatile with multi threading?
... synchronization, it does not create memory fences, nor does it ensure the order of execution of operations. It does not make operations atomic. It does not make your code magically thread safe. volatile may be the single-most misunderstood facility in all of C++. See this, this and this for mor...
Where does Scala look for implicits?
...mple of type class pattern. Another example on Scala's standard library is Ordering. There's a library that makes heavy use of this pattern, called Scalaz.
This is an example of its use:
def sum[T](list: List[T])(implicit integral: Integral[T]): T = {
import integral._ // get the implicits i...
Rolling median algorithm in C
...
I couldn't find a modern implementation of a c++ data structure with order-statistic so ended up implementing both ideas in top coders link suggested by MAK ( Match Editorial: scroll down to FloatingMedian).
Two multisets
The first idea partitions the data into two data structures (heaps, mu...
In what order do static/instance initializer blocks in Java run?
...ns several classes, each of which has a static initializer block. In what order do those blocks run? I know that within a class, such blocks are run in the order they appear in the code. I've read that it's the same across classes, but some sample code I wrote disagrees with that. I used this co...