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ReQL command: union

Command syntax

stream.union(sequence[, sequence, ...][, :interleave => true]) → stream

array.union(sequence[, sequence, ...][, :interleave => true]) → array

r.union(stream, sequence[, sequence, ...][, :interleave => true]) → stream

r.union(array, sequence[, sequence, ...][, :interleave => true]) → array

Description

Merge two or more sequences.

The optional interleave argument controls how the sequences will be merged:

  • true: results will be mixed together; this is the fastest setting, but ordering of elements is not guaranteed. (This is the default.)
  • false: input sequences will be appended to one another, left to right.
  • "field_name": a string will be taken as the name of a field to perform a merge-sort on. The input sequences must be ordered before being passed to union.
  • function: the interleave argument can take a function whose argument is the current row, and whose return value is a string to take as a field name, as with the "field_name" setting described above.

Example: Construct a stream of all heroes.

r.table('marvel').union(r.table('dc')).run(conn)

Example: Combine four arrays into one.

r.expr([1, 2]).union([3, 4], [5, 6], [7, 8, 9]).run(conn)

[1, 2, 3, 4, 5, 6, 7, 8, 9]

Example: Create a changefeed from the first example.

r.table('marvel').union(r.table('dc')).changes.run(conn)

Now, when any heroes are added, modified or deleted from either table, a change notification will be sent out.

Example: Merge-sort the tables of heroes, ordered by name.

r.table('marvel').order_by('name').union(
    r.table('dc').order_by('name'), :interleave => 'name'
).run(conn)

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