gistfile1.js

// Retrieve all the documents where val == 1
// If no document is returned, insert {newVal: 2}
// Else update all the documents with {newVal: 2}
//
// Note: This query is not atomic

r.table("test").filter({val: 1}).count().do(function(numResults) {
  return r.branch(
    numResults.eq(0),
    r.table("test").insert({newVal: 2}),
    r.table("test").filter({val: 1}).update({newVal: 2})
  )
})