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Created
May 12, 2011 13:45
Improving tags map/reduce with MongoDB 1.8.x
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class Tag | |
include Mongoid::Document | |
def self.rebuild | |
tags_before = Hash[ * Tag.all.collect { |tag| | |
[tag.name, tag] | |
}.flatten] | |
map = <<-EOS | |
function() { | |
if (this.tags != null) { | |
this.tags.forEach(function(t) { | |
emit(t, 1); | |
}); | |
} | |
} | |
EOS | |
reduce = <<-EOS | |
function(key, values) { | |
var count = 0; | |
values.forEach(function(v) { count += v; }); | |
return count; | |
} | |
EOS | |
tags_mapreduce = nil | |
tags_mapreduce_coll = nil | |
if collection.db.connection.server_version >= '1.7.4' | |
tags_mapreduce = TaggedModel.collection.map_reduce(map, reduce, { :raw => true, :out => { :inline => 1 } })['results'] | |
else | |
TaggedModel.collection.map_reduce(map, reduce, { out: 'tags_mapreduce' }) | |
tags_mapreduce_coll = Mongoid.master.collection('tags_mapreduce') | |
tags_mapreduce = tags_mapreduce_coll.find() | |
end | |
tags_after = [] | |
tags_mapreduce.each do |tag_mapreduce| | |
name = tag_mapreduce['_id'] | |
next if name.nil? | |
name = name.strip | |
next if name.blank? | |
tag = tags_before[name] | |
tag_mapreduce_count = tag_mapreduce['value'].to_i | |
if ! tag | |
Tag.create!(name: name, count: tag_mapreduce_count) | |
else | |
if (tag_mapreduce_count != tag.count) | |
tag.update_attribute(:count, tag_mapreduce_count) | |
end | |
end | |
tags_after << tag | |
end | |
(tags_before.values - tags_after).each do |tag| | |
tag.delete | |
end | |
tags_mapreduce_coll.drop if tags_mapreduce_coll | |
end | |
end |
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