On 11 Jan 2018, at 5:01pm, Matthew Towler <tow...@ccdc.cam.ac.uk> wrote:

> With versions prior to 3.8.0 the query returns in under a second (which is 
> very impressive!).  A query without all the sub-selects (so just selecting 
> some specific ID values from the main table) always works correctly (which is 
> why I had to include the long version in this message, for which apologies).

In your two versions, please prepend "EXPLAIN QUERY PLAN " to your SELECT 
command.  Do they both report the same query plan ?

> What I have found, and the reason I feel this is closely related to the bug I 
> mentioned earlier, is that if I delete the index ABUNDANCE_UNIQUE_DATA_INDEX 
> on the main table (a unique index on all the columns) the query works 
> perfectly on all versions I have tested.

Does the query plan remain the same when you delete the index ?

Simon.
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