Someone (twanger) sent me here from the IRC channel with the following:
I have a query that normally takes 0.150 seconds, but after an insert can take 14 seconds.
Here's the scenario:
Run this query: select * from cad_part left join smart_part using (cannon_part_id) where cad_import_id = 91 order by cad_part_reference_letter, cad_part_id
The result is returned in about 150ms.
Then I run my import operation which adds 1 new cad_import row, about 30 new cad_part rows, and about 100 new cad_line rows (which aren't involved in the above query). In this case, the new cad_import row has a PK of cad_import_id = 92.
When I run the query again (only the where clause changed): select * from cad_part left join smart_part using (cannon_part_id) where cad_import_id = 92 order by cad_part_reference_letter, cad_part_id
it takes about 14 seconds (and has a different plan).
I can repeat the first query (id=91) and it still executes in 150ms and then repeat the second query and in still takes ~14 seconds.
I've found two things that fix this. First, if I run analyze, the second query will take 150ms.
Second, if I set enable_nestloop to false the second query will use that same plan that the first does and complete in 150ms.
I've posted a bunch of details on my website including the size of the tables (all pretty small), both query plans, and some of the schema.
I also just redid the query without the final order by clause with the same results.
So I guess my question is, am I doing something wrong? did I miss an index or something? is this a bug (a 100x hit for not running analyze seems a little severe)? should I just run "analyze cad_part" after my inserts to that table?
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