Loop

Experimental

loop {step_function} {initial_relation}

Iteratively applies step function to initial relation until the step returns an empty table. Returns a relation that contains rows of initial relation and all intermediate relations.

This behavior could be expressed with following pseudo-code:

def loop(step, initial):
    result = []
    current = initial
    while current is not empty:
        result = append(result, current)
        current = step(current)

    return result

Examples

from_text format:json '[{"n": 1 }]'
loop (
    filter n<4
    select n = n+1
)

# returns [1, 2, 3, 4]

WITH table_0 AS (
  SELECT
    1 AS n
),
table_4 AS (
  WITH RECURSIVE loop AS (
    SELECT
      n
    FROM
      table_0 AS table_1
    UNION
    ALL
    SELECT
      n + 1
    FROM
      loop AS table_2
    WHERE
      n < 4
  )
  SELECT
    *
  FROM
    loop
)
SELECT
  n
FROM
  table_4 AS table_3