There's no compression. It's just a uncompressed sqlite database file. You need a sqlite db editor and learn some SQL to use this file.

Thanks for the answer.

There's no compression.

If so, why doesn't the size of the sqlite-file change (it remains equal to 48 kilobytes), no matter how many commands I enter in the console? The size of the sqlite-file does not change even after adding a few megabytes of text to the console.

You need a sqlite db editor

I was browsing the contents of the object_data table using DB Browser for SQL: http://i.imgur.com/T2sIsJu.png