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What is the “N+1 selects problem” in ORM (Object-Relational Mapping)?
...QL is now a heck of a lot better at handling them than it was when I first started using it.
These days, a simple join on a properly indexed set of tables is rarely a problem, in performance terms. And if it does give a performance hit, then the use of index hints often solves them.
This is discus...
Is recursion ever faster than looping?
... algorithm and reach a result?
We will establish a hierarchy of concepts, starting from scratch and defining in first place the basic, core concepts, then build second level concepts with those, and so on.
First Concept: Memory cells, storage, State. To do something you need places to store final...
MongoDB Many-to-Many Association
...
This can be achieved with a document which tells the application at the start (1) which roles the user belongs to and (2) where to get information about an event linked to a particular role.
{_id: ObjectID(),
roles: [[“Engineer”, “ObjectId()”],
[“Administrator”, ...
What is “callback hell” and how and why does RX solve it?
...ell can be avoided is to use FRP which is an "enhanced version" of RX.
I started to use FRP recently because I have found a good implementation of it called Sodium ( http://sodium.nz/ ).
A typical code looks like this ( Scala.js ) :
def render: Unit => VdomElement = { _ =>
<.div(
...
javascript: recursive anonymous function?
...Y (f => ([a, b, x]) =>
x === 0 ? a : f ([b, a + b, x - 1]))
// starting with 0 and 1, generate the 7th number in the sequence
console.log (fibonacci ([0, 1, 7]))
// 0 1 1 2 3 5 8 13
But this is bad because it's exposing internal state (counters a and b). It would be nice if we ...
Servlet returns “HTTP Status 404 The requested resource (/servlet) is not available”
...he error message is fine Googlable. In case you have no clue, best is to restart from scratch and do not touch any IDE/project configuration defaults. In case you're using Eclipse, you can find instructions in How do I import the javax.servlet API in my Eclipse project?
Testing the servlet individu...
GridLayout and Row/Column Span Woe
...
Starting from API 21, the GridLayout now supports the weight like LinearLayout. For details please see the link below:
https://stackoverflow.com/a/31089200/1296944
...
How can I prevent SQL injection in PHP?
...he source again. It's the destination that matters. The moment a developer starts to separate the sheep from the goats (thinking whether some particular variable is "safe" or not) he/she takes his/her first step towards disaster. Not to mention that even the wording suggests bulk escaping at the ent...
In practice, what are the main uses for the new “yield from” syntax in Python 3.3?
...own in Python. Dave Beazley's Curious Course on Coroutines is an excellent start. Read slides 24-33 for a quick primer.
Reading data from a generator using yield from
def reader():
"""A generator that fakes a read from a file, socket, etc."""
for i in range(4):
yield '<< %s' ...
Is “inline” without “static” or “extern” ever useful in C99?
...
Thanks, I'm starting to get the idea!
– Sven Marnach
Jun 10 '11 at 22:55
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