Using C++ 11 lambdas: #include <iostream> #include <vector> #include <numeric> // std::iota #include <algorithm> // std::sort, std::stable_sort using namespace std; template <typename T> vector<size_t> sort_indexes(const vector<T> &v) { // initialize original index locations vector<size_t> idx(v.size()); iota(idx.begin(), idx.end(), 0); // sort indexes based on comparing values in v // using std::stable_sort instead of std::sort // to … Read more
The primary key is always indexed. This is the same for MyISAM and InnoDB, and is generally true for all storage engines that at all supports indices.
Create some test data… create table test (a int, b int, c int, constraint pk_test primary key(a, b)); create table test2 (a int, b int, c int, constraint uk_test2 unique (b, c)); create table test3 (a int, b int, c int, constraint uk_test3b unique (b), constraint uk_test3c unique (c),constraint uk_test3ab unique (a, b)); List indexes … Read more
If you are using numpy, you have the argsort() function available: >>> import numpy >>> numpy.argsort(myList) array([0, 1, 2, 4, 3]) http://docs.scipy.org/doc/numpy/reference/generated/numpy.argsort.html This returns the arguments that would sort the array or list.
KEY and INDEX are synonyms in MySQL. They mean the same thing. In databases you would use indexes to improve the speed of data retrieval. An index is typically created on columns used in JOIN, WHERE, and ORDER BY clauses. Imagine you have a table called users and you want to search for all the … Read more
Mark this folder as Excluded in the File | Project Structure | Modules | Sources tab. Edit: also make sure it’s not added as a library in the project.
Yes, but only on innodb. Innodb is currently the only shipped table format that has foreign keys implemented.
Clustered Index Only one per table Faster to read than non clustered as data is physically stored in index order Non Clustered Index Can be used many times per table Quicker for insert and update operations than a clustered index Both types of index will improve performance when select data with fields that use the … Read more
You can use operator.itemgetter: from operator import itemgetter a = [-2, 1, 5, 3, 8, 5, 6] b = [1, 2, 5] print(itemgetter(*b)(a)) # Result: (1, 5, 5) Or you can use numpy: import numpy as np a = np.array([-2, 1, 5, 3, 8, 5, 6]) b = [1, 2, 5] print(list(a[b])) # Result: [1, … Read more
see docs: http://pandas.pydata.org/pandas-docs/stable/generated/pandas.DataFrame.insert.html using loc = 0 will insert at the beginning df.insert(loc, column, value) df = pd.DataFrame({‘B’: [1, 2, 3], ‘C’: [4, 5, 6]}) df Out: B C 0 1 4 1 2 5 2 3 6 idx = 0 new_col = [7, 8, 9] # can be a list, a Series, an array … Read more