Pros and cons

Why use Qt Test for unit testing and TDD (test-driven development)?

• small testing framework (about 6K lines of source code);
• seamless integration with QtCreator development environment;
• full support of Qt framework including classes/types and signal/slots;
• simple to start and use.

However, there are some drawbacks …

The Windows registry (WR) is a NoSQL DBMS based on a semi-structured hierarchical data model. Unlike configuration files approach, WR:

• can manage millions of keys and values
• is thread-safe
• is an in-memory database
• supports some data types
• supports a secure access to keys and values
• has GUI (regedit) and command …

Motivation

C++11 has introduced the move semantic which can also be used in containers instead of "old-school" pointers. The specific containers owning objects has been proposed earlier by third-party libraries like Boost (for example, ptr_map or ptr_vector).

The goal of the test is to compare the speed of manipulations …

SQL Server Profiler has the template "locks" that is intended especially to trace deadlock. Let's try to simulate and catch a deadlock situation.

Suppose the test database is named test. Create two tables and feed them some data.

USE test;

CREATE TABLE dbo.invoices (
   id int NOT NULL,
   num nvarchar …

Hash indexes are used as entry points for memory-optimized tables; both features were introduced in SQL Server 2014. Let's look at index performance in scenario "key-value store".

Scenario and environment

The table stores a significant volume (about 10 millions rows) of pairs key-value. The key is of integer type and …

The small test program shows how memory and file I/O operations can be accelerated using multiple threads.

Scenario

The program uses

• N threads (1 means a single thread)
• X bytes of memory to allocate a huge block (255 MB by default)
• M files to dump some huge memory block …

Some countries have integer numbers printed on the transport tickets, for example, in ex-USSR. The ticket is "happy" when the sum of the first half of digits equals to the second one. Then you should eat it and make a wish.

Example:

123456 and 111222 are not happy tickets
123123 …

As DBAs know, Database Tuning Advisor can help you in some cases.

• The analyze of the traces will be efficient in OLTP where the most of queries are repeating and could be generalized
• The analyze of traces will be less efficient in OLAP/reporting where the queries are parameterized by …

In theory, hash map structure should be very fast on retrieving by key operations, close to O(1) like for an array. A sorted map (keys are sorted) should be O(log₂ N) instead. The following test checks the difference.

Common scenario

We will use one tester class per …

Free Pascal (like Delphi) provide some useful functions to watch heap memory state in your application.

function GetHeapStatus: THeapStatus;

THeapStatus is documented here

Example of using this function is below

program ProgWatchMem;

uses
  Math, FGL;

type
  TLongIntArr = array of LongInt; // LongInt is a 4-byte signed integer
  PLongIntArr = ^TLongIntArr;
  TMySortedMap = specialize …