Transform nodes

Transform nodes allow you to change the output of the document type

rename

We can simply define this JSON schema.

[
    {
        "database": "book",
        "index": "book",
        "nodes": [
            {
                "table": "book",
                "columns": [
                    "isbn",
                    "title"
                ],
                "transform": {
                    "rename": {
                        "isbn": "book_isbn",
                        "title": "book_title"
                    }
                }
            }
        ]
    }
]

To get this document structure in Elasticsearch

[
    {
        "book_isbn": "9785811243570",
        "book_title": "Charlie and the chocolate factory"
    },
    {
        "book_isbn": "9788374950978",
        "book_title": "Kafka on the Shore"
    },
    {
        "book_isbn": "9781471331435",
        "book_title": "1984"
    }
]

mapping

You can specify the data type for an Elasticsearch field in the schema.

You can find the list of supported data types here

[
    {
        "database": "book",
        "index": "book",
        "nodes": [
            {
                "table": "book",
                "columns": [
                    "isbn",
                    "title"
                ],
                "transform": {
                    "mapping": {
                        "isbn": "long",
                        "title": "keyword"
                    }
                }
            }
        ]
    }
]

concat

You can concatenate multiple columns into a single field with an optional delimiter.

[
    {
        "database": "book",
        "index": "book",
        "nodes": [
            {
                "table": "book",
                "columns": [
                    "title",
                    "firstname",
                    "lastname"
                ],
                "transform": {
                    "concat": {
                        "columns": ["title", "firstname", "lastname"],
                        "destination": "fullname",
                        "delimiter": "-"
                    }
                }
            }
        ]
    }
]