* refactor sql planning to re-use expression virtual columns when possible when constructing a DruidQuery, allowing virtual columns to be defined in filter expressions, and making resulting native druid queries more concise. also minor refactor of built-in sql aggregators to maximize code re-use
* fix it
* fix it in the right place
* fixup for base64 stuff
* fixup tests
* fix merge conflict on import order
* fixup
* fix imports
* fix tests
* review comments
* refactor
* re-arrange
* better javadoc
* fixup merge
* fixup tests
* fix accidental changes
For selectors with internal caches (like SingleScanTimeDimensionSelector,
SingleLongInputCachingExpressionColumnValueSelector, etc) we can get a perf
boost and memory usage decrease by sharing selectors.
* integration-tests: make ITParallelIndexTest still work in parallel
Follow-up to #7181, which made the default behavior for index_parallel tasks
non-parallel.
* Validate that parallel index subtasks were run
* Reduce # of max subTasks to 2
* fix typo and add more doc
* add more doc and link
* change default and add warning
* fix doc
* add test
* fix it test
#### `EventReceiverFirehoseFactory`
Fixed several concurrency bugs in `EventReceiverFirehoseFactory`:
- Race condition over putting an entry into `producerSequences` in `checkProducerSequence()`.
- `Stopwatch` used to measure time across threads, but it's a non-thread-safe class.
- Use `System.nanoTime()` instead of `System.currentTimeMillis()` because the latter are [not suitable](https://stackoverflow.com/a/351571/648955) for measuring time intervals.
- `close()` was not synchronized by could be called from multiple threads concurrently.
Removed unnecessary `readLock` (protecting `hasMore()` and `nextRow()` which are always called from a single thread). Removed unnecessary `volatile` modifiers.
Documented threading model and concurrent control flow of `EventReceiverFirehose` instances.
**Important:** please read the updated Javadoc for `EventReceiverFirehose.addAll()`. It allows events from different requests (batches) to be interleaved in the buffer. Is this OK?
#### `TimedShutoffFirehoseFactory`
- Fixed a race condition that was possible because `close()` that was not properly synchronized.
Documented threading model and concurrent control flow of `TimedShutoffFirehose` instances.
#### `Firehose`
Refined concurrency contract of `Firehose` based on `EventReceiverFirehose` implementation. Importantly, now it states that `close()` doesn't affect `hasMore()` and `nextRow()` and could be called concurrently with them. In other words, specified that `close()` is for "row supply" side rather than "row consume" side. However, I didn't check that other `Firehose` implementatations adhere to this contract.
<hr>
This issue is the result of reviewing `EventReceiverFirehose` and `TimedShutoffFirehose` using [this checklist](https://medium.com/@leventov/code-review-checklist-java-concurrency-49398c326154).
Previously, the test validated that the data source that we ingested from still
had the same query responses that it did before the second ingestion. This is
less useful than validating queries against the newly created data source.
The new queries file differs from the old one in that its maxTime is earlier due
to the interval selected by the reindex, and in that it does not query for the
dropped metric "count".