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Scripts and data related Chromium's history
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verify_comments_and_patch_set_files_relationship not picking up index #56

Closed andymeneely closed 10 years ago

andymeneely commented 10 years ago

Postgres doesn't seem to be picking up the index on the verify verify_comments_and_patch_set_files_relationship.

If I run this on the test data set:

Comment.where.not(patch_set_file_id: PatchSetFile.select("id")).explain

I get the explain telling me that it's doing a table scan within a table scan on patch set files. 

EXPLAIN for: SELECT "comments".* FROM "comments"  WHERE ("comments"."patch_set_file_id" NOT IN (SELECT id FROM "patch_set_files"))
                                 QUERY PLAN
-----------------------------------------------------------------------------
 Seq Scan on comments  (cost=791.85..1068.94 rows=2764 width=226)
   Filter: (NOT (hashed SubPlan 1))
   SubPlan 1
     ->  Seq Scan on patch_set_files  (cost=0.00..722.68 rows=27668 width=4)`

I have no idea why, but maybe if we run this query a little differently?

This might be helpful: http://stackoverflow.com/questions/309786/how-do-i-force-postgres-to-use-a-particular-index