Class Sequel::Model::Associations::EagerGraphLoader
In: lib/sequel/model/associations.rb
Parent: Object

This class is the internal implementation of eager_graph. It is responsible for taking an array of plain hashes and returning an array of model objects with all eager_graphed associations already set in the association cache.

Methods

load   new  

Attributes

after_load_map  [R]  Hash with table alias symbol keys and after_load hook values
alias_map  [R]  Hash with table alias symbol keys and association name values
column_maps  [R]  Hash with table alias symbol keys and subhash values mapping column_alias symbols to the symbol of the real name of the column
dependency_map  [R]  Recursive hash with table alias symbol keys mapping to hashes with dependent table alias symbol keys.
limit_map  [R]  Hash with table alias symbol keys and [limit, offset] values
master  [R]  Hash with table alias symbol keys and callable values used to create model instances The table alias symbol for the primary model
primary_keys  [R]  Hash with table alias symbol keys and primary key symbol values (or arrays of primary key symbols for composite key tables)
reciprocal_map  [R]  Hash with table alias symbol keys and reciprocal association symbol values, used for setting reciprocals for one_to_many associations.
records_map  [R]  Hash with table alias symbol keys and subhash values mapping primary key symbols (or array of symbols) to model instances. Used so that only a single model instance is created for each object.
reflection_map  [R]  Hash with table alias symbol keys and AssociationReflection values
row_procs  [R]  Hash with table alias symbol keys and callable values used to create model instances
type_map  [R]  Hash with table alias symbol keys and true/false values, where true means the association represented by the table alias uses an array of values instead of a single value (i.e. true => *_many, false => *_to_one).

Public Class methods

Initialize all of the data structures used during loading.

[Source]

      # File lib/sequel/model/associations.rb, line 2132
2132:         def initialize(dataset)
2133:           opts = dataset.opts
2134:           eager_graph = opts[:eager_graph]
2135:           @master =  eager_graph[:master]
2136:           requirements = eager_graph[:requirements]
2137:           reflection_map = @reflection_map = eager_graph[:reflections]
2138:           reciprocal_map = @reciprocal_map = eager_graph[:reciprocals]
2139:           @unique = eager_graph[:cartesian_product_number] > 1
2140:       
2141:           alias_map = @alias_map = {}
2142:           type_map = @type_map = {}
2143:           after_load_map = @after_load_map = {}
2144:           limit_map = @limit_map = {}
2145:           reflection_map.each do |k, v|
2146:             alias_map[k] = v[:name]
2147:             type_map[k] = v.returns_array?
2148:             after_load_map[k] = v[:after_load] unless v[:after_load].empty?
2149:             limit_map[k] = v.limit_and_offset if v[:limit]
2150:           end
2151: 
2152:           # Make dependency map hash out of requirements array for each association.
2153:           # This builds a tree of dependencies that will be used for recursion
2154:           # to ensure that all parts of the object graph are loaded into the
2155:           # appropriate subordinate association.
2156:           @dependency_map = {}
2157:           # Sort the associations by requirements length, so that
2158:           # requirements are added to the dependency hash before their
2159:           # dependencies.
2160:           requirements.sort_by{|a| a[1].length}.each do |ta, deps|
2161:             if deps.empty?
2162:               dependency_map[ta] = {}
2163:             else
2164:               deps = deps.dup
2165:               hash = dependency_map[deps.shift]
2166:               deps.each do |dep|
2167:                 hash = hash[dep]
2168:               end
2169:               hash[ta] = {}
2170:             end
2171:           end
2172:       
2173:           # This mapping is used to make sure that duplicate entries in the
2174:           # result set are mapped to a single record.  For example, using a
2175:           # single one_to_many association with 10 associated records,
2176:           # the main object column values appear in the object graph 10 times.
2177:           # We map by primary key, if available, or by the object's entire values,
2178:           # if not. The mapping must be per table, so create sub maps for each table
2179:           # alias.
2180:           records_map = {@master=>{}}
2181:           alias_map.keys.each{|ta| records_map[ta] = {}}
2182:           @records_map = records_map
2183: 
2184:           datasets = opts[:graph][:table_aliases].to_a.reject{|ta,ds| ds.nil?}
2185:           column_aliases = opts[:graph_aliases] || opts[:graph][:column_aliases]
2186:           primary_keys = {}
2187:           column_maps = {}
2188:           models = {}
2189:           row_procs = {}
2190:           datasets.each do |ta, ds|
2191:             models[ta] = ds.model
2192:             primary_keys[ta] = []
2193:             column_maps[ta] = {}
2194:             row_procs[ta] = ds.row_proc
2195:           end
2196:           column_aliases.each do |col_alias, tc|
2197:             ta, column = tc
2198:             column_maps[ta][col_alias] = column
2199:           end
2200:           column_maps.each do |ta, h|
2201:             pk = models[ta].primary_key
2202:             if pk.is_a?(Array)
2203:               primary_keys[ta] = []
2204:               h.select{|ca, c| primary_keys[ta] << ca if pk.include?(c)}
2205:             else
2206:               h.select{|ca, c| primary_keys[ta] = ca if pk == c}
2207:             end
2208:           end
2209:           @column_maps = column_maps
2210:           @primary_keys = primary_keys
2211:           @row_procs = row_procs
2212: 
2213:           # For performance, create two special maps for the master table,
2214:           # so you can skip a hash lookup.
2215:           @master_column_map = column_maps[master]
2216:           @master_primary_keys = primary_keys[master]
2217: 
2218:           # Add a special hash mapping table alias symbols to 5 element arrays that just
2219:           # contain the data in other data structures for that table alias.  This is
2220:           # used for performance, to get all values in one hash lookup instead of
2221:           # separate hash lookups for each data structure.
2222:           ta_map = {}
2223:           alias_map.keys.each do |ta|
2224:             ta_map[ta] = [records_map[ta], row_procs[ta], alias_map[ta], type_map[ta], reciprocal_map[ta]]
2225:           end
2226:           @ta_map = ta_map
2227:         end

Public Instance methods

Return an array of primary model instances with the associations cache prepopulated for all model objects (both primary and associated).

[Source]

      # File lib/sequel/model/associations.rb, line 2231
2231:         def load(hashes)
2232:           master = master()
2233:       
2234:           # Assign to local variables for speed increase
2235:           rp = row_procs[master]
2236:           rm = records_map[master]
2237:           dm = dependency_map
2238: 
2239:           # This will hold the final record set that we will be replacing the object graph with.
2240:           records = []
2241: 
2242:           hashes.each do |h|
2243:             unless key = master_pk(h)
2244:               key = hkey(master_hfor(h))
2245:             end
2246:             unless primary_record = rm[key]
2247:               primary_record = rm[key] = rp.call(master_hfor(h))
2248:               # Only add it to the list of records to return if it is a new record
2249:               records.push(primary_record)
2250:             end
2251:             # Build all associations for the current object and it's dependencies
2252:             _load(dm, primary_record, h)
2253:           end
2254:       
2255:           # Remove duplicate records from all associations if this graph could possibly be a cartesian product
2256:           # Run after_load procs if there are any
2257:           post_process(records, dm) if @unique || !after_load_map.empty? || !limit_map.empty?
2258: 
2259:           records
2260:         end

[Validate]