* Enforce an invariant in our dependency checker so that logical plans never have duplicate output attribute names or ids.
* Fix ROW to not produce columns with duplicate names.
* Fix ResolveUnionTypes to not create multiple synthetic field attributes for the same union type.
* Add tests for commands using the same column name more than once.
* Update docs w.r.t. how commands behave if they are used with duplicate column names.
This copies the first line of the description of each command to just
under the syntax so that it's "in order", before the `Parameters`
section. That way if you are reading from top to bottom you see:
```
syntax
short description
parameter names and descriptions
long description
examples
```
I've also removed the `Description` section entirely if the description
was just one sentence. So in some cases that just isn't `long
description`.
* Break out 'Limitations' into separate page
* Add REST API docs
* Restructure commands, functions, and operators refs
* Add placeholder for getting started guide
* Group 'Syntax', 'Metafields', and 'MV fields' under 'Language'
* Add placeholder for Kibana page
* Add link from landing page
* Apply uniform formatting to ACOS, CASE, and DATE_PARSE function refs
* Reword default LIMIT
* Add support for COUNT(*)
* Move 'Commands' and 'Functions and operators' to individual pages
---------
Co-authored-by: Elastic Machine <elasticmachine@users.noreply.github.com>
