Re: 50 000 000 Table entries and I have to do a keyword search HELP NEEDED

One option that does not take advantage of any fancy indexing methods is
to create a trigger on the table, on insert/update/delete, which
extracts each individual word from the field you care about, and creates
an entry in another 'keyword' table, id = 'word', value = pk of your
original table. then index the keyword table on the 'keyword' field,
and do your searches from there. this should improve performance
substantially, even on very large return sets, because the keyword table
rows are very small and thus a lot of them fit in a disk block.

- Jeremy

-----Original Message-----
From: pgsql-performance-owner(at)postgresql(dot)org
[mailto:pgsql-performance-owner(at)postgresql(dot)org] On Behalf Of borajetta
Sent: Monday, June 07, 2004 5:47 PM
To: pgsql-performance(at)postgresql(dot)org
Subject: [PERFORM] 50 000 000 Table entries and I have to do a keyword
search HELP NEEDED

So I have a table with about 50 million entries in it, I have to do a
keyword search.

The keyword search is done on the title of the entry. For example a
entry could be "This is a title string which could be searched"

I have tried a few ways to search but I get horrible search times. Some
keywords will come up with matches as big as .25 million but most are
around 1000-5000.

I use an index which narrows the table down to about 1.5-2million
entries.

I used 2 tables which had a 1:1 correspondence.

One held a gist index which was on a int field which searched the for
the keyword. Then I would join the table to another to retrieve the
rest of the information about the items it matched.

This was slow even for returning 100 entries. About 10 seconds,
sometimes 5. But when I start getting 1xxx entries its about 30-50
seconds. The rest is just horrible.

How should I set up my indexes and or tables.

We were thinking of putting the index inside one table then the join
would not have to be done but this still returns rather slow results.

I have not fully tested this method but it looks like when run for just
the keyword search on the title and no joining it can return in about 10
seconds or less.

This is a great improvement but I am currently going to make the table
all in one and see how long it will take. I believe it will not be much
more as there will be no join needed only the returning of some
attribute fields.

This is still not the kind of time I would like to see, I wanted
something around 2 seconds or less. I know there is a lot of
information especially if .25 million rows are to be returned but if
there is only 1xxx-9xxx rows to be returned I believe 2 seconds seems
about right.

How do search engines do it?

Any suggestions are welcome,

Thanks