Thank you very much for all your inputs. I believe "analyze" is the one
I should use .
Quoth emilu@xxxxxxxxxxxxxxxxx (Emi Lu):
no. the suggestion was that a VACUUM is not needed, but that an
ANALYZE might be.
Thank you gnari for your answer. But I am a bit confused about not
running vacuum but only "analyze". Can I seperate these two
operations? I guess "vacuum analyze" do both vacuum and analyze. Or
"EXPLAIN ANALYZE" can do it for me?
EXPLAIN, ANALYZE, and VACUUM are different things; ANALYZE gets used
in two different contexts...
1. VACUUM is what cleans dead tuples out of tables.
e.g. VACUUM my_table;
2. VACUUM ANALYZE cleans out dead tuples and recalculates data
distributions
e.g. VACUUM ANALYZE my_table;
3. EXPLAIN describes query plans
e.g. EXPLAIN select * from my_table;
4. EXPLAIN ANALYZE compares query plan estimates to real results
e.g. EXPLAIN ANALYZE select * from my_table;
5. ANALYZE recalculates data distributions (as in 2, but without
cleaning out dead tuples).
e.g. ANALYZE my_table;
Pointedly, EXPLAIN ANALYZE is entirely distinct from ANALYZE and
VACUUM ANALYZE...
