Daniil Kirilyuk created QPID-8592:
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Summary: [Broker-J] Pass context value from parent query into the
subquery
Key: QPID-8592
URL: https://issues.apache.org/jira/browse/QPID-8592
Project: Qpid
Issue Type: Improvement
Components: Broker-J
Affects Versions: qpid-java-broker-8.0.6
Reporter: Daniil Kirilyuk
Current version of broker query engine doesn't support subqueries referencing
fields from the parent query. To support this possibility it's needed to pass
the context from parent query to the subquery.
To pass context from parent query to the subquery it's needed to add current
stream item and it's alias to the Evaluation context. It can be done using
Stream#peek() inside of SelectEvaluator#evaluate().
As the aliases from parent query will affect subquery sorting, it also will be
required to consider added aliases in QueryEvaluator#createComparator().
This should allow to use values from parent queries in subqueries, e.g.:
{code:java}
SELECT
id,
name,
(SELECT name FROM connection WHERE SUBSTRING(name, 1, POSITION(']' IN name)) =
'[' + SUBSTRING(c.name, 1, POSITION('|' IN c.name) - 1) + ']') as connection,
(SELECT id FROM connection WHERE SUBSTRING(name, 1, POSITION(']' IN name)) =
'[' + SUBSTRING(c.name, 1, POSITION('|' IN c.name) - 1) + ']') as connectionId,
(SELECT name FROM session WHERE id = c.session.id) as session
FROM consumer c{code}
or
{code:java}
SELECT
name,
destination,
(SELECT id FROM queue WHERE name = b.destination) AS destinationId,
exchange,
(SELECT id FROM exchange WHERE name = b.exchange) AS exchangeId
FROM binding b
WHERE name = 'broadcast.amqp_user1.xxx.#'{code}
or
{code:java}
SELECT
alias,
(SELECT COUNT(id) FROM queue WHERE POSITION(UPPER(c.alias) IN name) > 0) AS
queueCount
FROM certificate c{code}
This would allow to retrieve values from associated entities without firing
additional queries.
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