Julian Hyde created CALCITE-450:
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Summary: Drop join tables if lattice implies that it is safe
Key: CALCITE-450
URL: https://issues.apache.org/jira/browse/CALCITE-450
Project: Calcite
Issue Type: Bug
Reporter: Julian Hyde
Assignee: Julian Hyde
A lattice implies foreign and primary key constraints among the related tables.
Therefore certain semi-joins can be dropped.
For instance, given a lattice based on
{code:sql}
SELECT 1 FROM sales_fact JOIN customer USING (customer_id)
{code}
the query
{code:sql}
SELECT s.product_id
FROM sales_fact AS s,
customer AS c
WHERE s.customer_id = c.customer_id
{code}
can be simplified to
{code:sql}
SELECT s.product_id
FROM sales_fact AS s
WHERE s.customer_id IS NOT NULL
{code}
even if no materializations are enabled.
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