Serguei_Tarassov's blog

Agile or not agile

Bertrand Meyer's article "Making sense of agile methods" (PDF, November 2017)
Russian translation published in "Open systems" magazine N°2-2018 "Об Agile по гамбургскому счету"

Some citations (I'm completely agreed according to my experience).

Everything will look fine until you suddenly discover that the next user story conflicts with previously implemented ones, and you have to go back and rethink everything

SQL Server: temporary tables and constraint names

Local temporary tables are isolated in the scope of current session regardless its name. It means that #temp_table in the session 1 is not the same that #temp_table in the session 2. However, the names of constraints are stored in the metadata of tempdb and can produce duplicate name errors.

SQL Server: key-value store table and hash index

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 value is a small random string.

The table store is used :

  • random read of a value from a key
  • random update of a value by a key

We will tests the scenario for the following types of table :

SQL: generate random character string

Collection of methods to generate random string in a single SQL statement

M1: Recursive string concatenation

On SQL Server the method is limited by 100 characters owing to the recursion level limitation. The method has the performance issues when using in loops/joins because the table always have 100 rows generated every time.


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