Tutorial by Examples: r

Getting started with a simple map

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Using a table valued parameter to insert multiple rows to a table

First, define a used defined table type to use: CREATE TYPE names as TABLE ( FirstName varchar(10), LastName varchar(10) ) GO Create the stored procedure: CREATE PROCEDURE prInsertNames ( @Names dbo.Names READONLY -- Note: You must specify the READONLY ) AS INSERT INTO d...

Expressing the power of 2

For expressing the power of 2 (2^n) of integers, one may use a bitshift operation that allows to explicitly specify the n. The syntax is basically: int pow2 = 1<<n; Examples: int twoExp4 = 1<<4; //2^4 int twoExp5 = 1<<5; //2^5 int twoExp6 = 1<<6; //2^6 ... int twoEx...

Installing PostgreSQL on Windows

While it's good practice to use a Unix based operating system (ex. Linux or BSD) as a production server you can easily install PostgreSQL on Windows (hopefully only as a development server). Download the Windows installation binaries from EnterpriseDB: http://www.enterprisedb.com/products-services-...

A Basic Importer

Assume you have a custom file you want to create an importer for. It could be an .xls file or whatever. In this case we're going to use a JSON file because it's easy but we're going to pick a custom extension to make it easy to tell which files are ours? Let's assume the format of the JSON file is ...

Using the right-left or spiral rule to decipher C declaration

The "right-left" rule is a completely regular rule for deciphering C declarations. It can also be useful in creating them. Read the symbols as you encounter them in the declaration... * as "pointer to" - always on the left side [] as "array of" ...

Creating a WeakMap object

WeakMap object allows you to store key/value pairs. The difference from Map is that keys must be objects and are weakly referenced. This means that if there aren't any other strong references to the key, the element in WeakMap can be removed by garbage collector. WeakMap constructor has an optional...

Removing an element with the key

To remove an element with a specified key, use the .delete() method. It returns true if the element existed and has been removed, otherwise false. const obj1 = {}, obj2 = {}; const weakmap = new WeakMap([[obj1, 7]]); console.log(weakmap.delete(obj1)); // true console.log(weakmap.has(obj...

Compile docker with checkpoint and restore enabled (ubuntu)

In order to compile docker its recommended you have at least 2 GB RAM. Even with that it fails sometimes so its better to go for 4GB instead. make sure git and make is installed sudo apt-get install make git-core -y install a new kernel (at least 4.2) sudo apt-get install linux-generic...

Checkpoint and Restore a Container

# create docker container export cid=$(docker run -d --security-opt seccomp:unconfined busybox /bin/sh -c 'i=0; while true; do echo $i; i=$(expr $i + 1); sleep 1; done') # container is started and prints a number every second # display the output with docker logs $cid # checkpoint the cont...

Using standard SQL directly with models

To use SQL syntax with model, that would transfer result to proper instantions, you should use directly one of Phalcon\Mvc\Model\Resultset classes: $users = new \Application\Models\Users(); // bitwise operation on `flag` field $sql = 'SELECT * FROM phorum.users WHERE (15 & (1 <&...

Create Memory Optimized Table

-- Create demo database CREATE DATABASE SQL2016_Demo ON PRIMARY ( NAME = N'SQL2016_Demo', FILENAME = N'C:\Dump\SQL2016_Demo.mdf', SIZE = 5120KB, FILEGROWTH = 1024KB ) LOG ON ( NAME = N'SQL2016_Demo_log', FILENAME = N'C:\Dump\SQL2016_Demo_log.ldf', ...

Show created .dll files and tables for Memory Optimized Tables

SELECT OBJECT_ID('MemOptTable1') AS MemOptTable1_ObjectID, OBJECT_ID('MemOptTable2') AS MemOptTable2_ObjectID GO SELECT name,description FROM sys.dm_os_loaded_modules WHERE name LIKE '%XTP%' GO Show all Memory Optimized Tables: SELECT name,type_desc,durability_desc,...

Memory-Optimized Table Types and Temp tables

For example, this is traditional tempdb-based table type: CREATE TYPE dbo.testTableType AS TABLE ( col1 INT NOT NULL, col2 CHAR(10) ); To memory-optimize this table type simply add the option memory_optimized=on, and add an index if there is none on the original type: CREATE TYPE dbo....

Declare Memory-Optimized Table Variables

For faster performance you can memory-optimize your table variable. Here is the T-SQL for a traditional table variable: DECLARE @tvp TABLE ( col1 INT NOT NULL , Col2 CHAR(10) ); To define memory-optimized variables, you must first create a memory-optimized table type and...

The use of "i" or "j" as imaginary unit, loop indices or common variable.

Recommendation Because the symbols i and j can represent significantly different things in MATLAB, their use as loop indices has split the MATLAB user community since ages. While some historic performance reasons could help the balance lean to one side, this is no longer the case and now the choice...

CREATE Temporal Tables

CREATE TABLE dbo.Employee ( [EmployeeID] int NOT NULL PRIMARY KEY CLUSTERED , [Name] nvarchar(100) NOT NULL , [Position] varchar(100) NOT NULL , [Department] varchar(100) NOT NULL , [Address] nvarchar(1024) NOT NULL , [AnnualSalary] decimal (10,2) NOT NULL ...

How do I query temporal data?

SELECT * FROM Employee FOR SYSTEM_TIME BETWEEN '2014-01-01 00:00:00.0000000' AND '2015-01-01 00:00:00.0000000' WHERE EmployeeID = 1000 ORDER BY ValidFrom;

Return actual value specified point in time(FOR SYSTEM_TIME AS OF )

Returns a table with a rows containing the values that were actual (current) at the specified point in time in the past. SELECT * FROM Employee FOR SYSTEM_TIME AS OF '2016-08-06 08:32:37.91'

Compile Feature Requirements

Required compiler features can be specified on a target using the command target_compile_features: add_library(foo foo.cpp ) target_compile_features(foo PRIVATE # scope of the feature cxx_constexpr # list of features ) The features must be part of CMAKE_C_COMPILE_FE...

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