GitHub user fhueske opened a pull request:
https://github.com/apache/flink/pull/2044
[FLINK-3944] [tableAPI] Add rewrite rules to reorder Cartesian products and
joins.
The Table API / SQL interface do not reorder joins due to missing stats and
estimates.
This can lead to situations where a query with two inner equi joins cannot
be executed due to missing support for Cartesian products. For instance the
following query would not be executed:
```
SELECT *
FROM t1, t2, t3
WHERE t1.a = t3.a AND t2.b = t3.b
```
because the plan would first compute the Cartesian product of `t1` and
`t2` because both are listed first in the `FROM` clause.
This PR adds optimization rules to reorder joins and Cartesian products to
resolve such situation.
You can merge this pull request into a Git repository by running:
$ git pull https://github.com/fhueske/flink tableCrossOrder
Alternatively you can review and apply these changes as the patch at:
https://github.com/apache/flink/pull/2044.patch
To close this pull request, make a commit to your master/trunk branch
with (at least) the following in the commit message:
This closes #2044
----
commit 760ffe29bc1e2f4462f453f378c06c7b1f980dee
Author: Fabian Hueske <[email protected]>
Date: 2016-05-27T11:04:12Z
[FLINK-3944] [tableAPI] Add rewrite rules to reorder Cartesian products and
joins.
These rules are necessary to resolve join orders that initially contain
Cartesian products
due to the order in which base relations are added in the FROM clause (SQL)
or joined (Table API).
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