On 19/11/24 12:34, Laurenz Albe wrote:
On Tue, 2024-11-19 at 11:53 +0100, Moreno Andreo wrote:
What about if query becomes
SELECT foo1, foo2 FROM bar WHERE (POSITION(foo1 IN 'blah blah') >0)
You could create an index like
CREATE INDEX ON bar (position(foo1 IN 'blah blah'));
Alternatively, you could have a partial index:
CREATE INDEX ON bar (foo1) INCLUDE (foo2)
WHERE position(foo1 IN 'blah blah') > 0;
Interesting. Never seen this form, I'll look further on it.
I stumbled into
https://www.cybertec-postgresql.com/en/indexing-like-postgresql-oracle/
and discovered text_pattern_ops.
I'm wondering if it can be of any use in my index, that should hold a
WHERE condition with a combination of LIKE and the POSITION expression
above.
More docs to read ... :-)
I don't think "text_pattern_ops" will help here - queries that use LIKE
to search for a substring (LIKE '%string%') cannot make use of a b-tree
index.
Oh, OK, i was happy to use BTREEs 'cause I had some issues with GIN/GIST (like indexes way bigger than table and so inefficient). OK, I'll stick with these and try harder to obtain better results.
One thing I can't understand well.
In
https://www.cybertec-postgresql.com/en/join-strategies-and-performance-in-postgresql/ you say
"
Note that for inner joins there is no distinction between the join condition and the WHERE condition, but that doesn't hold for outer joins."
What do you mean?
Thanks
Moreno
