Optimizing MySQL query with nested select statements? - mysql

Question

I've got read-only access to a MySQL database, and I need to loop through the following query about 9000 times, each time with a different $content_path_id. I'm calling this from within a PERL script that's pulling the '$content_path_id's from a file.
SELECT an.uuid FROM alf_node an WHERE an.id IN
(SELECT anp.node_id FROM alf_node_properties anp WHERE anp.long_value IN
(SELECT acd.id FROM alf_content_data acd WHERE acd.content_url_id = $content_path_id));
Written this way, it's taking forever to do each query (approximately 1 minute each). I'd really rather not wait 9000+ minutes for this to complete if I don't have to. Is there some way to speed up this query? Maybe via a join? My current SQL skills are embarrassingly rusty...

Answer 1

This is an equivalent query using joins. It depends what indexes are defined on the tables how this will perform.
If your Perl interface has the notion of prepared statements, you may be able to save some time by preparing once and executing with 9000 different binds.
You could also possibly save time by building one query with a big acd.content_url_id In ($content_path_id1, $content_path_id2, ...) clause
Select
an.uuid
From
alf_node an
Inner Join
alf_node_properties anp
On an.id = anp.node_id
Inner Join
alf_content_data acd
On anp.long_value = acd.id
Where
acd.content_url_id = $content_path_id

Answer 2

Try this extension to Laurence's solution which replaces the long list of OR's with an additional JOIN:
Select
an.uuid
From alf_node an
Join alf_node_properties anp
On an.id = anp.node_id
Join alf_content_data acd
On anp.long_value = acd.id
Join (
select "id1" as content_path_id union all
select "id2" as content_path_id union all
/* you get the idea */
select "idN" as content_path_id
) criteria
On acd.content_url_id = criteria.content_path_id
I have used SQL Server syntax above but you should be able to translate it readily.