Elasticsearch script - variable not defined - elasticsearch

Question

I'm following an Elasticsearch tutorial, but ran into a problem when trying to use parameters in a script.
Step 1: Create a new document - OK (index = website; type = blog; id = 1)
curl -XPUT localhost:9200/website/blog/1?pretty -d '{
"title":"my first post",
"tags" : [ "tag1" ]
}'
Step 2: Use script to append an extra value to tags array - ERROR
curl -XPOST localhost:9200/website/blog/1/_update?pretty -d '{
"script" : "ctx._source.tags+=new_tag",
"params" : {
"new_tag" : "tag2"
}
}'
The error message is this, mentioning "reason" : "Variable [new_tag] is not defined." But I have defined the variable new_tag as described on the tutorial page. What am I doing wrong?
"error" : {
"root_cause" : [
{
"type" : "remote_transport_exception",
"reason" : "[mrukUvA][127.0.0.1:9300][indices:data/write/update[s]]"
}
],
"type" : "illegal_argument_exception",
"reason" : "failed to execute script",
"caused_by" : {
"type" : "script_exception",
"reason" : "compile error",
"caused_by" : {
"type" : "illegal_argument_exception",
"reason" : "Variable [new_tag] is not defined."
},
"script_stack" : [
"ctx._source.tags+=new_tag",
" ^---- HERE"
],
"script" : "ctx._source.tags+=new_tag",
"lang" : "painless"
}
},
"status" : 400
}
Step 2 (retry) Qualifying new_tag with params - ERROR
curl -XPOST localhost:9200/website/blog/1/_update?pretty -d '{
"script" : {
"inline": "ctx._source.tags+=params.new_tag",
"params" : {
"new_tag" : "tag2"
}
}
}'
Gives error
{
"error" : {
"root_cause" : [
{
"type" : "remote_transport_exception",
"reason" : "[mrukUvA][127.0.0.1:9300][indices:data/write/update[s]]"
}
],
"type" : "illegal_argument_exception",
"reason" : "failed to execute script",
"caused_by" : {
"type" : "script_exception",
"reason" : "runtime error",
"caused_by" : {
"type" : "class_cast_exception",
"reason" : "Cannot cast java.lang.String to java.util.ArrayList"
},
"script_stack" : [
"ctx._source.tags+=params.new_tag",
" ^---- HERE"
],
"script" : "ctx._source.tags+=params.new_tag",
"lang" : "painless"
}
},
"status" : 400
}
As a sanity check to make sure the document is valid
$ curl -XGET localhost:9200/website/blog/1?pretty
{
"_index" : "website",
"_type" : "blog",
"_id" : "1",
"_version" : 27,
"found" : true,
"_source" : {
"title" : "my first post",
"tags" : [
"tag1"
]
}
}
So the document does have the valid field tag which is an array.

Answer 1

Your syntax is slightly off, if you have parameters you need to inline the script. Try this:
curl -XPOST localhost:9200/website/blog/1/_update?pretty -d '{
"script" : {
"inline": "ctx._source.tags.add(params.new_tag)",
"params" : {
"new_tag" : "tag2"
}
}
}'

Answer 2

you can use "inline" although it is deprecated. now you alse can use "source" to replace "inline" for no warnings. for example:
"script" : {
"source": "ctx._source.tags.add(params.new_tag)",
"params": {
"new_tag":"tag1"
}
}