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Transform
editTransform
editDeprecated in 2.0.0.
The document can be transformed before it is indexed by registering a script in
the transform element of the mapping. The result of the transform is indexed
but the original source is stored in the _source field.
This was deprecated in 2.0.0 because it made debugging very difficult. As of now there really isn’t a feature to use in its place other than transforming the document in the client application.
Deprecated or no, here is an example:
{
"example" : {
"transform" : {
"script" : {
"inline": "if (ctx._source['title']?.startsWith('t')) ctx._source['suggest'] = ctx._source['content']",
"params" : {
"variable" : "not used but an example anyway"
},
"lang": "groovy"
}
},
"properties": {
"title": { "type": "string" },
"content": { "type": "string" },
"suggest": { "type": "string" }
}
}
}
Its also possible to specify multiple transforms:
{
"example" : {
"transform" : [
{"script": "ctx._source['suggest'] = ctx._source['content']"},
{"script": "ctx._source['foo'] = ctx._source['bar'];"}
]
}
}
Because the result isn’t stored in the source it can’t normally be fetched by source filtering. It can be highlighted if it is marked as stored.