Tutorial by Examples: r

This will create a composite index of both keys, mystring and mydatetime and speed up queries with both columns in the WHERE clause. CREATE INDEX idx_mycol_myothercol ON my_table(mycol, myothercol) Note: The order is important! If the search query does not include both columns in the WHERE claus...

Most developers encounter backpressure when their application fails with MissingBackpressureException and the exception usually points to the observeOn operator. The actual cause is usually the non-backpressured use of PublishSubject, timer() or interval() or custom operators created via create(). ...

Collections in Java only work for objects. I.e. there is no Map<int, int> in Java. Instead, primitive values need to be boxed into objects, as in Map<Integer, Integer>. Java auto-boxing will enable transparent use of these collections: Map<Integer, Integer> map = new HashMap<&g...

public static class ArrayHelpers { public static bool Contains<T>(this T[] array, T[] candidate) { if (IsEmptyLocate(array, candidate)) return false; if (candidate.Length > array.Length) return false; for (int a = 0; a <...

redis-cli is the Redis command line interface program that allows to send commands to Redis and read the replies sent by the server, directly from the terminal. Basic command line usage is below: Access to redis: $ redis-cli 127.0.0.1:6379> Access to redis with authentication: $ redis-cli ...

The dir() function can be used to get a list of the members of a class: dir(Class) For example: >>> dir(list) ['__add__', '__class__', '__contains__', '__delattr__', '__delitem__', '__dir__', '__doc__', '__eq__', '__format__', '__ge__', '__getattribute__', '__getitem__', '__gt__', '__...

The trim() method returns a new String with the leading and trailing whitespace removed. String s = new String(" Hello World!! "); String t = s.trim(); // t = "Hello World!!" If you trim a String that doesn't have any whitespace to remove, you will be returned the same S...

If efficiency is important, a fast way to iterate over pixels in a cv::Mat object is to use its ptr<T>(int r) method to obtain a pointer to the beginning of row r (0-based index). According to the matrix type, the pointer will have a different template. For CV_8UC1: uchar* ptr = image.ptr&...

By default, most of the information is hidden from the user. You can use -v switches to get a verbose log of the connection attempt, which will usually pinpoint the problem by showing why the behavior is different than you expect. Let's assume you are connecting to the server example.com using ssh ...

ISO/ANSI SQL: SELECT Id, Col1 FROM TableName ORDER BY Id OFFSET 20 ROWS MySQL: SELECT * FROM TableName LIMIT 20, 42424242424242; -- skips 20 for take use very large number that is more than rows in table Oracle: SELECT Id, Col1 FROM (SELECT Id, Col1, row_num...

ISO/ANSI SQL: SELECT * FROM TableName FETCH FIRST 20 ROWS ONLY; MySQL; PostgreSQL; SQLite: SELECT * FROM TableName LIMIT 20; Oracle: SELECT Id, Col1 FROM (SELECT Id, Col1, row_number() over (order by Id) RowNumber FROM TableName) WHERE RowNumber <= 2...

ISO/ANSI SQL: SELECT Id, Col1 FROM TableName ORDER BY Id OFFSET 20 ROWS FETCH NEXT 20 ROWS ONLY; MySQL: SELECT * FROM TableName LIMIT 20, 20; -- offset, limit Oracle; SQL Server: SELECT Id, Col1 FROM (SELECT Id, Col1, row_number() over (order by Id) RowNumbe...

See also the Mercurial Tutorial Creating a Mercurial Repository A Mercurial repository is simply a directory (referred to as the "working directory") containing an .hg directory with metadata about the contents of the repository. This makes Mercurial very lightweight and easy to start us...

DESCRIBE and EXPLAIN are synonyms. DESCRIBE on a tablename returns the definition of the columns. DESCRIBE tablename; Exmple Result: COLUMN_NAME COLUMN_TYPE IS_NULLABLE COLUMN_KEY COLUMN_DEFAULT EXTRA id int(11) NO PRI 0 ...

android { ... defaultConfig {...} buildTypes {...} productFlavors { demo { applicationId "com.example.myapp.demo" versionName "1.0-demo" } full { applicationId "com.example.myapp.full"...

In this example, we have a Countries table. A table for countries has many uses, especially in Financial applications involving currencies and exchange rates. Live example: SQL fiddle Some Market data software applications like Bloomberg and Reuters require you to give their API either a 2 or 3 ch...

<?php /** * Panel: WPCustomize * * Basic Customizer panel with basic controls. * * @since 1.0.0 * @package WPC */ // Exit if accessed directly. if ( ! defined( 'ABSPATH' ) ) { exit; } // Customize function. if ( ! function_exists( 'wpc_panel_wpcustomize' ) ) { ...

Panels can have sections, sections can have settings, and settings can have controls. Settings are saved in the database, while the controls for particular settings are only used to display their corresponding setting to the user. This code creates a basic section in the panel from above. Inside a...

Add typings to your package.json { ... "typings": "path/file.d.ts" ... } Now when ever that library is imported typescript will load the typings file

Add the following code to functions.php to remove it from everyone except the Administrator user level: add_action('after_setup_theme', 'no_admin_bar'); function no_admin_bar() { if (!current_user_can('administrator') && !is_admin()) { show_admin_bar(false); ...