How does Apple find SMS records in search?

The operation steps of searching for SMS records by Apple mobile phone are as follows:

Find the general options in the phone settings, and click to enter the general options.

Review the Spotlight search options in the General tab, and then click Enter.

After entering the Spotlight search tab, find the information option and open the information.

Then enter the short message content in the "Spotlight search" box to show off the search, and you can see the short message you need to search below.