I want to sort the search result collection by product attribute value.

**Scenario:** 

I have created a custom attribute called "**product_category**" as a drop down attribute.

Which has the following options, 

  1.Unit.

  2.Component

  3.Bundle

So once We search any product I need to load the product created with "**Unit**" option first for the particular keyword match.

**Example:**

3 products are created with below information.

1. Unit Test product - **product_category** attribute value is set as "**Unit**".

2. Test bundle product - **product_category** attribute value is set as "**Bundle**".

3. Test component product - **product_category** attribute value is set as "**Component**".

So whenever i searched the keyword, "**Test Product**" I need to load the product where **product_category** attribute value is set as "**Unit**" on top in search result page.

Can anyone help me how this can be achieved? Thanks in advance!!