Code changes:
- In the lookup-based extractionFns, inherit injective property from
the lookup itself if not specified.
Doc changes:
- Add a "Query execution" section to the lookups doc explaining how
injective lookups and their optimizations work.
- Remove scary warnings against using registeredLookup extractionFns.
They are necessary and important since they work with filters and
function cascades -- two things that the dimension specs do not do.
They deserve to be first class citizens.
- Move the "registeredLookup" fn above the "lookup" fn. It's probably
more commonly used, so the docs read better this way.
- Add central doc for multi-value dimensions, with some content from other docs.
- Link to multi-value dimension doc from topN and groupBy docs.
- Fixes a broken link from dimensionspecs.md, which was presciently already
linking to this nonexistent doc.
- Resolve inconsistent naming in docs & code (sometimes "multi-valued", sometimes
"multi-value") in favor of "multi-value".
* Adds kafka, URI, and JDBC namespace defintions
* Add ability to explicitly rename using a "namespace" which is a particular data collection that is loaded on all realtime, historic nodes, and brokers. If any of these nodes has the namespace extension, ALL nodes have the namespace extension.
* Add namespace caching and populating (can be on heap or off heap)
* Add NamespaceExtractionCacheManager for handling caches
* Added ExtractionNamespace for handling metadata on the extraction namespaces
* Added ExtractionNamespaceUpdate for handling metadata related to updates
* Add extension which caches renames from a kafka stream (requires kafka8)
* Added README.md for the namespace kafka extension
* Added docs
* Added namespace/size, namespace/count, namespace/deltaTasksStarted metrics
Add static config for namespaces via `druid.query.extraction.namespace`
* This is a rebase of https://github.com/b-slim/druid/tree/static_config_only