Making sure wp term relationships records are unique

Question

Which' WordPress function is used in programmatically associating the term taxonomy IDs with post IDs?

And does that function have internal mechanisms to make sure no duplicate entries are allowed even if the records were to be added programmatically?

Here of course I'm not talking about wpdb->insert.

Answer 1

While the code does check for duplicates, the schema itself won't allow it because the term_relationships table has a PRIMARY KEY of (object_id,term_taxonomy_id).

Answer 2

I believe the function you are looking for is wp_set_object_terms(). You will need to ensure that you are not giving duplicate IDs when append is set to false. I'm not sure what the behavior is when append is set to true.

EDIT: Having read through the source code for the function, it looks like if you're appending, then it does check for duplicates.