On 03/11/11 19:19, Florian Pflug wrote:
There's a difference between values of type tsvector, and what GIN indices on columns or expressions of type tsvector store.
I was wondering what was the point about storing the tsvector in the table, I now understand. I then should use the GIN index to rank my documents, and work on the stored tsvectors for positions.
As I pointed out above, you'll first need to make sure to store the result of to_tsvector in a columns. Then, what you need seems to be a functions that takes a tsvector value and returns the contained lexems as individual rows. Postgres doesn't seem to contain such a function currently (don't believe that, though - go and recheck the documentation. I don't know all thousands of built-in functions by heart). But it's easy to add one. You could either use PL/pgSQL to parse the tsvector's textual representation, or write a C function. If you go the PL/pgSQL route, regexp_split_to_table() might come in handy.
This seems easier to program than what I was thinking about, I'm going to do that. But I'm wondering about size of database with the GIN index plus the tsvector column, and performance about parsing the whole tsvectors for each document I need positions from (as I need them for a very few terms).
Maybe some external fulltext engine managing lexemes and positions would be more efficient for my purpose. I'll try some different things and let you know the results.
Thanks all for your help Regards, Yoann Moreau -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
