Field Modification Operators.md

Field modification operators

incl: specify a key name or an array of key names that you want to include in the join. If the incl option is used only the keys specified in incl will be joined.

-or-

excl: sometimes it is simpler to specify the fields you want to exclude from the join. Use excl to specify a key name or an array of key names that you want to exclude from the join.

The incl operator and excl operator are mutually exclusive.

xlt: this is an array of translation objects. Each object contains 2 keys, "old" and "new":

{"old": "<src keyname>" "new": "<new keyname>"}

In essence, this is a way to rename a field and put it into the calculated table.

subObj: sometimes it is useful to group all source fields into a sub-object. This can be accomplished with the subObj parameter. subObj can be used in conjunction with xlt to put translated incl fields into the subObj.

Notes:

• * fields are required.
• only one of incl or excl can be specified. If both are specified an error will be thrown.
• For all operations you can use mongo dot notation to refer to sub keys. key.subkey specifies the subkey of the key object.

Example specification:

[{
    "table": "<name of 1st table>",
    "common": "<this tables common key>",
  }, {
    "table": "<name of 2nd table>",
    "common": "<this tables common key>",
    "incl": "oneKey"
  }, {
    "table": "<name of 3rd table>",
    "common": "<this tables common key>",
    "incl": ["_id", "name", "address"]
    "xlt": [{"old": "_custID", "new": "custname"}, {"old": "src", "new": "translation"}]
  },
  ...
    "table": "<name of table n>",
    "common": "<this table's common key>",
    "excl": ["<key1 to exclude>", "<key2 to exclude>"]
    "subobj": "parts"
  }]