On 2013-02-23, Raymond C. Rodgers <sinful622@xxxxxxxxx> wrote: > On 02/23/2013 05:26 AM, Tom Lane wrote: >> A "virtual" tsvector like that is probably going to be useless for >> searching as soon as you get a meaningful amount of data, because the >> only way the DB can implement a search is to compute the tsvector >> value for each table row and then examine it for the target word(s). >> What you want is a GIST or GIN index on the contents of the tsvector. > I think the only real advantage to using something like this would be a > space savings in terms of storing the tsvector data, but I don't see > that being a significant enough reason to go ahead and use this idea in > a production situation. As mentioned [by pretty much all of us], once > the table size is sufficiently large there would be a performance > penalty by to_tsvector being executed on every record in the table. Unless the plan comes out as a table scan the index will be used instead ot to_tsvector() When there is a table scan to_tsvector will be used instead of reading from disk, I don't know how fast to_tsvector is compared to disk, but usually computing a result is faster than reading it from disk. Storing the tsvector in the table is likely to be faster only when a tablescan is done and the table is fully cached in ram. -- ⚂⚃ 100% natural -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
