On 2018/01/17 8:48 AM, Nick wrote:
Thank you Simon.
As you said, UNIQUE(b, i) is redundant, but I guess it will not affect the
performance of the SELECT.
I find "SEARCH TABLE t1 USING INDEX sqlite_autoindex_t1_1 (b>?)" when I use
EXPLAIN QUERY PLAN, so I do not need to add any index, right?
Um, I guess I have nothing to do to improve the performance.
Thanks.
Hang on a second - True, there is nothing to be done to improve the
speed of that specific Query - BUT - there is plenty to be done to
improve the speed of the database for your specific use case. The usual
suspects that comes to mind are:
1. Use a faster Journal mode (Have to weigh speed against
power-loss-data-integrity-protection),
2. Use an in-memory DB (especially if you only reading from it)
3. Start a transaction and hold the DB read locks for the duration of
your application (again, if it won't need writing)
4. Ensure there are no other time-consuming bits of code in the sqlite
api RESET()-STEP() loop. (And if you are accessing it through a wrapper,
stop that and use the api directly).
We could and would probably give more useful direct advice if we know a
lot more about your specific use case, platforms, access-method and setup.
Cheers!
Ryan
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