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https://issues.jboss.org/browse/TEIID-2381?page=com.atlassian.jira.plugin...
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Steven Hawkins commented on TEIID-2381:
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Mark -
Other than disambiguating the current syntax as a hint that properly
belongs on the Query object rather than the first column object, I think it's separate
from the other issues.
It's two-fold, the primary concern is the placement on subqueries, union branches,
with clause items, etc. The secondary is for sources that support more complicated
positional hints, such as a column hint. The primary is fairly feasible. Arbitrary
positions however are currently not.
don't understand your third point or I'm confusing your
first and third points. Maybe provide an example illustrating this?
The first and the third are somewhat related. If you restrict the first to only full
queries that presumably are not able to be pushed with the parent, then they can all be
associated with their respective push-down. If you want a hint to appear in a push-down
subqueries, that would require additional translator support - e.g. a query and its
subquery both have hints and are pushed together - "SELECT /\*+ sh ... \*/ ...
(SELECT /\*+ sh ... \*/ ... ) FROM ..." such that the pushdown has both hints.
the propagation rules can be straightforward
Ignoring optimization yes. However the optimizer free for example to remove view layers.
For example if you have two views each with their own source hint and you join them
together. The optimizer removes the view layers and reorders the join. Where do the
hints apply and why?
I would simply add public Iteratable<String> getSourceHints()
to the API
That is one possibility. The optimizer could just collect all seemingly applicable hints
and leave it up to the translator to decide.
Expanded source hint support
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Key: TEIID-2381
URL:
https://issues.jboss.org/browse/TEIID-2381
Project: Teiid
Issue Type: Enhancement
Components: Query Engine
Reporter: Steven Hawkins
Assignee: Steven Hawkins
Attachments: HintsExecutionFactory.java, RandomExecutionFactory.java,
RandomNumberStoredProcedureExecution.java, SysviewHintsExecutionTest.java
We currently look at the source hint in only the root user query (not in subqueries nor
the with clause) and only consider it in a very narrow set of circumstances when it's
used in a view.
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