Optimization of IN with nested SELECT
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Key: DERBY-4007
URL: https://issues.apache.org/jira/browse/DERBY-4007
Project: Derby
Issue Type: Bug
Components: Performance
Affects Versions: 10.3.1.4
Environment: Linux
Reporter: Mikkel Kamstrup Erlandsen
Priority: Minor
The problem is with the following query:
UPDATE summa_records SET base='foobar' WHERE id IN ( SELECT parentId FROM
summa_relations WHERE childId='horizon_2615441');
It takes in the order of 30s to run when we expect something in the order of
1-2ms.
We have a setup with two tables
summa_records: 1,5M rows
summa_relations: ~350000 rows
summa_records have and 'id' column that is also indexed and is the primary key.
The summa_relations table holds mappings between different ids.
In our case the nested SELECT produces 2 hits, say, 'foo' and 'bar'. So the
UPDATE on these two hits should be quite snappy. If we run the SELECT alone it
runs in an instant, and also if we run with hardcoded ids for the IN clause:
UPDATE summa_records SET base='foobar' WHERE id IN ('foo', 'bar');
We have instant execution. I'll attach a query plan in a sec.
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