* This shows that only the `/` returns a valid JSON object. `/keys` and `/values` do not return a valid JSON object.
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#### Fixed the bug ...
* Fixed the return values for `/keys` and `/values` endpoints to return a valid JSON object
* As seen in the test case updates, the return values are valid JSON objects
* Additionally, in this PR, we are also updating the documentation for Globally cached lookups `/version` endpoint.
* As discussed in the linked issue, we are explicitly stating that the `/version` endpoint returns the internal cache scheduler's version and not the user facing version for the lookup.
* It is also helpful to the reader to note that the version is returned only for Globally cached lookups (`cachedNamespace`) and not for map lookup.
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#### Release note
Fixed: Map Lookup Introspection API endpoints `/keys` and `/values` no longer return an invalid JSON object.
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<hr>
##### Key changed/added classes in this PR
* `MapLookupExtractorFactory.java`
* `LookupIntrospectionResourceTest.java`
<hr>
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- [X] been tested in a test Druid cluster.
Fixes #17361.
Description
/keysand/valuesfor Map Lookup do not return valid JSON objects./keysreturnsjq: parse error: Invalid numeric literal at line 1, column 4
curl -X GET http://localhost:8888/druid/v1/lookups/introspect/sampleMapLookup/values | jq
jq: parse error: Invalid numeric literal at line 1, column 12
curl -X GET http://localhost:8888/druid/v1/lookups/introspect/sampleMapLookup | jq { "CA": "California", "NY": "New York", "WA": "Washington" }
$ echo '["key","key2"]' | jq [ "key", "key2" ]
$ echo '["value","value2"]' | jq [ "value", "value2" ]