Hi,
Le 15 juil. 09 à 02:01, Glen Parker a écrit :
Sounds to me like another reason to separate index definition from
creation. If an index can be defined but not yet created or valid,
then you could imagine syntax like:
DEFINE INDEX blahblah1 ON mytable (some fields);
DEFINE INDEX blahblah2 ON mytable (some other fields);
[RE]INDEX TABLE mytable;
...provided that REINDEX TABLE could recreate all indexes
simultaneously as you suggest.
Well to me it sounded much more like:
BEGIN;
CREATE INDEX idx_a ON t(a) DEFERRED;
CREATE INDEX idx_b ON t(b) DEFERRED;
COMMIT;
And at commit time, PostgreSQL would build all the transaction indexes
in one pass over the heap, but as Tom already pointed out, using only
1 CPU. Maybe that'd be a way to limit the overall io bandwidth usage
while not consuming too many CPU resources at the same time.
I mean now we have a choice to either sync scan the table heap on
multiple CPU, saving IO but using 1 CPU per index, or to limit CPU to
only 1 but then scan the heap once per index. The intermediary option
of using 1 CPU while still making a single heap scan sure can be
worthwhile to some?
Regards,
--
dim
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