No, that order doesn’t matter (or at least: shouldn’t matter). Any decent query optimizer will look at all the parts of the WHERE clause and figure out the most efficient way to satisfy that query. I know the SQL Server query optimizer will pick a suitable index – no matter which order you have your … Read more
The answer was no, sealed classes do not perform better than non-sealed. 2021: The answer is now yes there are performance benefits to sealing a class. Sealing a class may not always provide a performance boost, but the dotnet team are adopting the rule of sealing all internal classes to give the optimiser the best … Read more
Either I don’t understand your question, or Enumerable#find is the thing you were looking for.
Its interesting to run this benchmark with xdebug disabled, as xdebug adds quite a lot of overhead, esp to function calls. This is FGM’s script run using 5.6 With xdebug ForEach : 0.79232501983643 MapClosure: 4.1082420349121 MapNamed : 1.7884571552277 Without xdebug ForEach : 0.69830799102783 MapClosure: 0.78584599494934 MapNamed : 0.85125398635864 Here there is only a very small … Read more
A “correlated subquery” (i.e., one in which the where condition depends on values obtained from the rows of the containing query) will execute once for each row. A non-correlated subquery (one in which the where condition is independent of the containing query) will execute once at the beginning. The SQL engine makes this distinction automatically. … Read more
Why is x**4.0 faster than x**4 in Python 3*? Python 3 int objects are a full fledged object designed to support an arbitrary size; due to that fact, they are handled as such on the C level (see how all variables are declared as PyLongObject * type in long_pow). This also makes their exponentiation a … Read more
In perl, they result in the same opcodes: $ perl -MO=Concise -e ‘for(;;) { print “foo\n” }’ a <@> leave[1 ref] vKP/REFC ->(end) 1 <0> enter ->2 2 <;> nextstate(main 2 -e:1) v ->3 9 <2> leaveloop vK/2 ->a 3 <{> enterloop(next->8 last->9 redo->4) v ->4 – <@> lineseq vK ->9 4 <;> nextstate(main 1 … Read more
Scala makes it very easy to use enormous amounts of memory without realizing it. This is usually very powerful, but occasionally can be annoying. For example, suppose you have an array of strings (called array), and a map from those strings to files (called mapping). Suppose you want to get all files that are in … Read more
Several of the answers in the question you link talk about rewriting the code to be branchless and thus avoiding any branch prediction issues. That’s what your updated compiler is doing. Specifically, clang++ 10 with -O3 vectorizes the inner loop. See the code on godbolt, lines 36-67 of the assembly. The code is a little … Read more
The most voted answer so far is not wrong, but it doesn’t go into the depth I like to see and provides no scientific evidence. The Spring Boot team went through an exercise for reducing startup time for Boot 2.0, and ticket 11226 contains a lot of useful information. There is also a ticket 7939 … Read more