Subject | RE: [firebird-support] Re: Slow query (unindexed reads) |
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Author | Svein Erling Tysvær |
Post date | 2011-06-22T12:49:55Z |
>> Stop thinking tables, start thinking datasets!Good to hear that my suspicions were wrong. The query you showed us should take a few seconds and absolutely not 7 minutes (unless we're talking huge blobs), show us the real query (with the plan and some information about the selectivity of indexes) and we'll see whether we can spot anything.
>>
>> Indexes are useful in WHERE and JOIN clauses, selects that return entire tables normally don't
>> benefit much from using an index (it might be a bit quicker or slower, but the difference isn't huge).
>In this case I need to traverse the whole table - and I join to a couple of others for lookup values.
>It is not for display, and there are a few WHERE clauses in the final query. The real query takes over
>7 minutes..which is totally unacceptable. I pared it right down to see if the non indexed read is the
>problem. As far as I can see, the indexes are not being used.
>
>When I do a join on another table - THAT table also reads in in non indexed as well (even though there
>are indexes on the join fields). Same problem, I am thinking.
>
>I do not care about the ORDER BY - I don't care about the order the records are processed in. I simply
>use it to try and force the use of an index. It did not work in this case, but I seem to recall it
>working in other cases.
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