On 2010-12-21 10:42, Massa, Harald Armin wrote:
b) creating an index requires to read the data-to-be-indexed. So, to have an
index pointing at the interesting rows for your query, the table has to be
read ... which would be the perfect time to allready select the interesting
rows. And after having the interesting rows: the index is worthless
... until another similar query comes along, when suddenly it's a massive win.
Why not auto-create indices for some limited period after database load
(copy? any large number of inserts from a single connection?), track those
that actually get re-used and remove the rest? Would this not provide
a better out-of-the-box experience for neophytes?
[...]
Why is the query planner not allowed to create indexes, but only allowed to
use or not use what's available?
as in b): Creating an index is quite expensiv
How much more so than doing that full-table-scan plus sort, which your
query is doing anyway?
Cheers,
Jeremy
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