Some more examples for the cookbook

Here are some possible solutions to problems I have helped users solve. It might help them if they were in the cookbook or the secondary index page.

Filter by one field and order by another

A naive query would look like

.filter(r.row['a'] == val).orderBy('b')

It is tempting to try to optimize it like this, but it doesn't work because explanation.

.indexCreate('a')
.indexCreate('b')
.getAll(val, {index: 'a'}).orderBy({index: 'b'}) # error

A compound index could be used instead.

.indexCreate('a_b', [r.row('a'), r.row('b')])
.between([val, r.minval], [val, r.maxval], {index: 'a_b'}).orderBy({index: 'a_b'})

Tags

Disjunction:

.indexCreate('tags', {multi: true})
.getAll('hunting', 'fishing', {index: 'tags'})

Conjuntion:

.indexCreate('tags_powerset',
    r.row('tags').orderBy(function(a){return a}).map(
        function(elem){ return [[], [elem]]}).reduce(function(as,bs){
            return as.concatMap(function(a){ return bs.map(function(b){ return a.add(b)})})}),
  {multi: true})
.getAll(r.expr(['cooking', 'asia']).orderBy(r.row), {index: 'tags_powerset'})

Multiple queries in a single request

Homogeneous write queries:

var query = function(param){ return ... };
r.expr([1,2,3,'a','b']).forEach(query)

Homogeneous read queries:

var query = function(param){ return ... };
r.expr([1,2,3,'a','b']).concatMap(query)

Heterogeneous queries:

var query1 = function(){ return ... };
var query2 = function(query1_result){ return ... /* a stream */ };
var query3 = function(query2_result){ return ... });
query1().do(function(query1_result){
    return query2(query1_result).coerceTo('array').do(function(query2_result){
        return query3(query2_result)})})

Review the supplied examples and locate the cookbook or secondary index page mentioned in the issue. Check how existing examples are organized and add the filtering, tags, and multiple-query material in the appropriate documentation location. Done means the examples are integrated consistently and the relevant page navigation or index is updated if needed.