ReQL command: union

Command syntax

stream.union(sequence[, sequence, ...]) → stream
array.union(sequence[, sequence, ...]) → array
r.union(stream, sequence[, sequence, ...]) → stream
r.union(array, sequence[, sequence, ...]) → array

Description

Merge two or more sequences.

The interleave optArg 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 optArg can take a function whose argument is the current row, and whose return value is a value to perform a merge-sort on.

Example: Construct a stream of all heroes.

r.table("marvel").union(r.table("dc")).run(conn);

Example: Combine four arrays into one.

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

// Result:
[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").orderBy("name")
 .union(r.table("dc").orderBy("name")).optArg("interleave", "name")
 .run(conn);