clintropolis opened a new pull request #10041:
URL: https://github.com/apache/druid/pull/10041
### Description
This PR extends #10020 to more correctly only convert a `TableDataSource` to
a `GlobalTableDataSource` if it is also joinable. In service to this, the
`JoinableFactory` interface has been modified to add a new method:
```
boolean isDirectlyJoinable(DataSource dataSource);
```
which should return `true` if for a `JoinableFactory` and a `DataSource` may
possibly produce a `Joinable` for at least some `JoinAnalysis`, directly, that
is without a subquery join. This is useful, because `DataSource.isGlobal` is
used to determine whether or not a subquery is necessary to complete the join.
Secondly, it adds automatic conversion of `TableDataSource` to
`GlobalTableDataSource` for native druid queries whenever eligible, to make
`GlobalTableDataSource` an internal construct.
To make these changes visible, the INFORMATION_SCHEMA.TABLES table now has
an additional column, working name of `TABLE_AVAILABILITY`. Making up values
for table types for this new column in the middle of the night, I came up with:
* `DataSource.isGlobal == false` - `DISTRIBUTED`
* `DataSource.isGlobal == true` - `GLOBAL`
* Views - `VIRTUAL`
* Information Schema and System Schema tables - `LOCAL`
Any suggestions welcome, I have not documented this yet, pending discussion
and some searching to determine if there are any analogs to something like this
in other systems. This was done as an alternative to making
`GlobalTableDataSource` be a new `TABLE_TYPE`, since they are still in fact a
table.
<hr>
This PR has:
- [ ] been self-reviewed.
- [ ] using the [concurrency
checklist](https://github.com/apache/druid/blob/master/dev/code-review/concurrency.md)
(Remove this item if the PR doesn't have any relation to concurrency.)
- [ ] added documentation for new or modified features or behaviors.
- [ ] added Javadocs for most classes and all non-trivial methods. Linked
related entities via Javadoc links.
- [ ] added or updated version, license, or notice information in
[licenses.yaml](https://github.com/apache/druid/blob/master/licenses.yaml)
- [ ] added comments explaining the "why" and the intent of the code
wherever would not be obvious for an unfamiliar reader.
- [ ] added unit tests or modified existing tests to cover new code paths,
ensuring the threshold for [code
coverage](https://github.com/apache/druid/blob/master/dev/code-review/code-coverage.md)
is met.
- [ ] added integration tests.
- [ ] been tested in a test Druid cluster.
<!-- Check the items by putting "x" in the brackets for the done things. Not
all of these items apply to every PR. Remove the items which are not done or
not relevant to the PR. None of the items from the checklist above are strictly
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<hr>
##### Key changed/added classes in this PR
* `ClientQuerySegmentWalker`
* `JoinableFactory` and implementations
* `DruidSchema`
* `InformationSchema`
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