hi,
I created an index with text_pattern_ops because I want fast prefix search [1]
[2].
CREATE INDEX ON mytable USING BTREE (state, city, address text_pattern_ops);
(Note it's composite - I'm looking for prefixes on the address part only.) I
can see that it "works" (purely uses the index) for prefix searches without
column references:
# explain select 1 from mytable where state = 'x' and city = 'x' and address
like 'asd%';
QUERY PLAN
--
Index Only Scan using mytable_state_city_house_number_and_s_idx1 on mytable
(cost=0.41..4.44 rows=1 width=4)
Index Cond: ((state = 'x'::text) AND (city = 'x'::text) AND (address ~>=~
'asd'::text) AND (address ~<~ 'ase'::text))
Filter: (address ~~ 'asd%'::text)
(3 rows)
...but I don't think it's working when I use a column reference || '%'... I say
that because "address" no longer appears in the "Index Cond":
# explain select (select 1 from mytable where state = 'x' and city = 'x' and
address like generate_series.generate_series::text || '%') t2 from
generate_series(0, 10);
QUERY PLAN
--
Function Scan on generate_series (cost=0.00..4455.00 rows=1000 width=4)
SubPlan 1
-> Index Only Scan using mytable_state_city_house_number_and_s_idx1 on
mytable (cost=0.41..4.44 rows=1 width=4)
Index Cond: ((state = 'x'::text) AND (city = 'x'::text))
Filter: (address ~~ ((generate_series.generate_series)::text ||
'%'::text))
(5 rows)
Any advice? I'm on 10.3. Also, has this changed between 9.6 and 10.3?
And... maybe I'm asking the wrong question, how can I do a fast search on
state, city, address prefix?
Thanks,
Seamus
[1] http://blog.cleverelephant.ca/2016/08/pgsql-text-pattern-ops.html
[2] https://blog.2ndquadrant.com/text-search-strategies-in-postgresql/
