SQL Server

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 :

Fast inserting a file into a table

How to insert fast a file (i.e. binary one) from disk to a SQL Server table?

Certainly the SQL Server account should have a corresponding permissions to access the file on the disk. For example I take the file C:\WINDOWS\system32\oembios.bin having the size about 12 MB. For really big files you'd better switch to the FILESTREAM approach.

Indexing columns of bit type

Clearly, an index build on only one column of the bit type is useless because the selectivity is poor (50% of a table in average). However, when a table has several columns of the bit type, the composite index may be efficient.

For the test example, we'll create a table and fill it with random data.

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