mongo-ruby-driver/lib/mongo/collection.rb

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# --
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# Copyright (C) 2008-2009 10gen Inc.
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#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
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#
# http://www.apache.org/licenses/LICENSE-2.0
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#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
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# ++
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require 'mongo/query'
module XGen
module Mongo
module Driver
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# A named collection of records in a database.
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class Collection
attr_reader :db, :name, :hint
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def initialize(db, name)
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@db, @name = db, name
@hint = nil
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end
# Set hint fields to use and return +self+. hint may be a single field
# name, array of field names, or a hash (preferably an OrderedHash).
# May be +nil+.
def hint=(hint)
@hint = normalize_hint_fields(hint)
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self
end
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# Return records that match a +selector+ hash. See Mongo docs for
# details.
#
# Options:
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# :fields :: Array of collection field names; only those will be returned (plus _id if defined)
# :offset :: Start at this record when returning records
# :limit :: Maximum number of records to return
# :sort :: Either hash of field names as keys and 1/-1 as values; 1 ==
# ascending, -1 == descending, or array of field names (all
# assumed to be sorted in ascending order).
# :hint :: See #hint. This option overrides the collection-wide value.
def find(selector={}, options={})
fields = options.delete(:fields)
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fields = nil if fields && fields.empty?
offset = options.delete(:offset) || 0
limit = options.delete(:limit) || 0
sort = options.delete(:sort)
hint = options.delete(:hint)
if hint
hint = normalize_hint_fields(hint)
else
hint = @hint # assumed to be normalized already
end
raise RuntimeError, "Unknown options [#{options.inspect}]" unless options.empty?
@db.query(self, Query.new(selector, fields, offset, limit, sort, hint))
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end
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# Find the first record that matches +selector+. See #find.
def find_first(selector={}, options={})
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h = options.dup
h[:limit] = 1
cursor = find(selector, h)
cursor.next_object # don't need to explicitly close b/c of limit
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end
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# Save an updated +object+ to the collection, or insert it if it doesn't exist already.
def save(object)
id = object[:_id] || object['_id']
if id.nil? || find_first({'_id' => id}).nil?
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insert(object)
else
modify({:_id => id}, object)
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end
end
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# Insert +objects+, which are hashes. "<<" is aliased to this method.
# Returns either the single inserted object or a new array containing
# +objects+. The object(s) may have been modified by the database's PK
# factory, if it has one.
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def insert(*objects)
objects = objects.first if objects.size == 1 && objects.first.is_a?(Array)
res = @db.insert_into_db(@name, objects)
res.size > 1 ? res : res.first
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end
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alias_method :<<, :insert
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# Remove the records that match +selector+.
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def remove(selector={})
@db.remove_from_db(@name, selector)
end
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# Remove all records.
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def clear
remove({})
end
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# Update records that match +selector+ by applying +obj+ as an update.
# If no match, inserts (???).
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def repsert(selector, obj)
@db.repsert_in_db(@name, selector, obj)
end
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# Update records that match +selector+ by applying +obj+ as an update.
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def replace(selector, obj)
@db.replace_in_db(@name, selector, obj)
end
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# Update records that match +selector+ by applying +obj+ as an update.
# Both +selector+ and +modifier_obj+ are required.
def modify(selector, modifier_obj)
raise "no object" unless modifier_obj
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raise "no selector" unless selector
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@db.modify_in_db(@name, selector, modifier_obj)
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end
# Create a new index. +field_or_spec+
# should be either a single field name or a Array of [field name,
# direction] pairs. Directions should be specified as
# XGen::Mongo::ASCENDING or XGen::Mongo::DESCENDING.
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# +unique+ is an optional boolean indicating whether this index
# should enforce a uniqueness constraint.
def create_index(field_or_spec, unique=false)
@db.create_index(@name, field_or_spec, unique)
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end
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# Drop index +name+.
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def drop_index(name)
@db.drop_index(@name, name)
end
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# Drop all indexes.
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def drop_indexes
# just need to call drop indexes with no args; will drop them all
@db.drop_index(@name, '*')
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end
# Drop the entire collection. USE WITH CAUTION.
def drop
@db.drop_collection(@name)
end
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# Perform a query similar to an SQL group by operation.
#
# Returns an array of grouped items.
#
# :keys :: list of fields to group by
# :condition :: specification of rows to be considered (as a 'find'
# query specification)
# :initial :: initial value of the aggregation counter object
# :reduce :: aggregation function as a JavaScript string
def group(keys, condition, initial, reduce)
group_function = <<EOS
function () {
var c = db[ns].find(condition);
var map = new Map();
var reduce_function = #{reduce};
while (c.hasNext()) {
var obj = c.next();
var key = {};
for (var i in keys) {
key[keys[i]] = obj[keys[i]];
}
var aggObj = map[key];
if (aggObj == null) {
var newObj = Object.extend({}, key);
aggObj = map[key] = Object.extend(newObj, initial);
}
reduce_function(obj, aggObj);
}
return {"result": map.values()};
}
EOS
return @db.eval(Code.new(group_function,
{
"ns" => @name,
"keys" => keys,
"condition" => condition,
"initial" => initial
}))["result"]
end
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# Return an array of hashes, one for each index. Each hash contains:
#
# :name :: Index name
#
# :keys :: Hash whose keys are the names of the fields that make up
# the key and values are integers.
#
# :ns :: Namespace; same as this collection's name.
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def index_information
@db.index_information(@name)
end
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# Return a hash containing options that apply to this collection.
# 'create' will be the collection name. For the other possible keys
# and values, see DB#create_collection.
def options
@db.collections_info(@name).next_object()['options']
end
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# Return the number of records that match +selector+. If +selector+ is
# +nil+ or an empty hash, returns the count of all records.
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def count(selector={})
@db.count(@name, selector || {})
end
protected
def normalize_hint_fields(hint)
case hint
when String
{hint => 1}
when Hash
hint
when nil
nil
else
h = OrderedHash.new
hint.to_a.each { |k| h[k] = 1 }
h
end
end
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end
end
end
end