Multiple Row Functions

A multiple row function is a function that returns multiple rows.

Multiple row function can only be used in the SELECT clause of a query and only allowed 1 multiple rows function in the clause for now.

UNNEST

unnest(array)

The unnest function is used to expand an array into multiple rows. The argument column must be an array. This function will expand the array into multiple rows as a returned result. If the item in the array is map[string]interface object, then it will be built as columns in the result rows.

Examples

Create a stream demo and have below inputs

{
  "a": [
    1,
    2
  ],
  "b": 3
}

Rule to get the unnest values:

SQL: SELECT unnest(a) FROM demo
___________________________________________________
{"unnest":1}
{"unnest":2}

Rule to get the unnest values with other columns:

SQL: SELECT unnest(a), b FROM demo
___________________________________________________
{"unnest":1, "b":3}
{"unnest":2, "b":3}

Create a stream demo and have below inputs

{
  "x": [
    {
      "a": 1,
      "b": 2
    },
    {
      "a": 3,
      "b": 4
    }
  ],
  "c": 5
}

Rule to get the unnest values with other columns:

SQL: SELECT unnest(x), c FROM demo
___________________________________________________
{"a":1, "b":2, "c": 5}
{"a":3, "b":4, "c": 5}

Extract

extract(map[string]interface{})

The argument must be a map object. This function expands the argument map and places it on the current row.

Example

Create a stream called demo and give it the following input.

{
  "data": {
    "k1": "v1",
    "k2": "v2"
  }
}

Rule to get the extract result:

SQL: SELECT extract(data) FROM demo
__________________________________________________
{"k1":"v1","k2":"v2"}