what is tts_isempty in postgres

In PostgreSQL, `tts_isempty` is a function related to the Text Search (TS) system. It's specifically used for managing and querying full-text search indexes. The `tts_isempty` function checks whether a given text search term or token set is empty or not. When called on an index or a term, it returns `true` if there are no indexed terms within that set, and `false` otherwise.

Here's a basic usage example:

SELECT tts_isempty('my_index', 'some_search_term');

This query would return `true` if there's no match for 'some_search_term' in the 'my_index'.

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file.isEmpty()

The `file.isEmpty()` method is not a standard method in Java. It is possible that it is a custom method that has been created in a specific program or library. Without further context, it is difficult to determine what this method does or what it returns.