What does "GIN doesn't support full index scans" mean? I'm a RDBMS newbie and I have a PostgreSQL database of more than 50 millions lines, growing everyday. There is a column 'text', which contains human-generated text of around 20 words. I need to be able to retrieve the texts containing a word or two belonging to a pre-set, almost 'constant', list of words.

I believe that the best to do so is to use full text search, based on my own dictionary and configuration, with a GIN or GiST index. That was for some context.

The pgsql doc states:


  GIN doesn't support full index scans.


I don't understand what that means.
Does it mean that if I query the word 'hello' it is possible that a line which text contains the word 'hello' could be not returned?

That would not be great, I'd rather be positive that I get exactly and fully what I want.

Thanks,

Arthur
a word or two belonging to a pre-set, almost 'constant', list of
  words.


Have you considered scanning the texts as they are input and flagging them (possibly with a many-to-many link to another table containing your list of keywords)?