Ah, very good. Thanks to you both.
I will definitly try this. Sounds like it may help.
Tim
On 3/20/2012 2:36 PM, Simon Slavin wrote:
On 20 Mar 2012, at 6:11pm, Tim Morton<[email protected]> wrote:
I may try this, but the topics are usually just one word each so I doubt an
index could reduce it much.
Max's trick is something that takes advantage of how SQLite works entirely. If
you do a SELECT like
SELECT id,topics FROM dictionary ORDER BY topics
and there's an index like
CREATE INDEX dti ON dictionary (topics,id)
then SQLite will use that index to find the right order to retrieve the records
in. But having figured out what rows it needs it realises that it has all the
information -- both the id and the topic -- right there in the index. So it
doesn't bother then looking up the TABLE data to fetch the other columns, it
just returns all the information you asked for right from the index it's
already looking at. It's fast and, because the index contains only the data
you want, it's equivalent to making up a separate table which has just the id
and topics columns.
I forgot about that trick when I replied but Max didn't.
Simon.
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