attribute length via ingest node

gistfile1.txt

# Create our mapping with a single attribute array: projects
PUT abac-ingest-node-test
{
	"mappings": {
		"doc": {
			"properties": {
				"projects": {
					"type": "keyword"
				}
			}
		}
	}
}

# Define pipeline to create a new projects_count field
PUT _ingest/pipeline/abac-test
{
	"description": "abac test",
	"processors": [
		{
			"script": {
				"inline": "ctx.projects_count = ctx.projects.length"
			}
		}
	]
}

# Load docs
POST abac-ingest-node-test/doc?pipeline=abac-test
{
	"projects": ["project-a","project-b"]
}
POST abac-ingest-node-test/doc?pipeline=abac-test
{
	"projects": ["project-a","project-b", "project-c"]
}

# Notice the correctly formed project_count field
GET abac-ingest-node-test/_search