um das mit dem funktionalen Index, Explain & einer besseren DB mal sehr einfach zu zeigen:
[code]
postgres=# create table obiast(ts timestamp);
CREATE TABLE
postgres=# create index idx_date on obiast (date_trunc('date',ts));
CREATE INDEX
postgres=#
postgres=#
postgres=# explain select * from obiast where date_trunc('date',ts) between current_date and current_date + 3;
QUERY PLAN
-------------------------------------------------------------------------------------------------------------------------------
Bitmap Heap Scan on obiast (cost=4.28..15.11 rows=11 width=8)
Recheck Cond: ((date_trunc('date'::text, ts) >= CURRENT_DATE) AND (date_trunc('date'::text, ts) <= (CURRENT_DATE + 3)))
-> Bitmap Index Scan on idx_date (cost=0.00..4.27 rows=11 width=0)
Index Cond: ((date_trunc('date'::text, ts) >= CURRENT_DATE) AND (date_trunc('date'::text, ts) <= (CURRENT_DATE + 3)))
(4 rows)
postgres=#
[/code]
