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

new(dataset)

Initialize all of the data structures used during loading.

[Source]

          # File lib/sequel/model/associations.rb, line 2191
    2191:         def initialize(dataset)
    2192:           opts = dataset.opts
    2193:           eager_graph = opts[:eager_graph]
    2194:           @master =  eager_graph[:master]
    2195:           requirements = eager_graph[:requirements]
    2196:           reflection_map = @reflection_map = eager_graph[:reflections]
    2197:           reciprocal_map = @reciprocal_map = eager_graph[:reciprocals]
    2198:           @unique = eager_graph[:cartesian_product_number] > 1
    2199:
    2200:           alias_map = @alias_map = {}
    2201:           type_map = @type_map = {}
    2202:           after_load_map = @after_load_map = {}
    2203:           limit_map = @limit_map = {}
    2204:           reflection_map.each do |k, v|
    2205:             alias_map[k] = v[:name]
    2206:             type_map[k] = v.returns_array?
    2207:             after_load_map[k] = v[:after_load] unless v[:after_load].empty?
    2208:             limit_map[k] = v.limit_and_offset if v[:limit]
    2209:           end
    2210:
    2211:           # Make dependency map hash out of requirements array for each association.
    2212:           # This builds a tree of dependencies that will be used for recursion
    2213:           # to ensure that all parts of the object graph are loaded into the
    2214:           # appropriate subordinate association.
    2215:           @dependency_map = {}
    2216:           # Sort the associations by requirements length, so that
    2217:           # requirements are added to the dependency hash before their
    2218:           # dependencies.
    2219:           requirements.sort_by{|a| a[1].length}.each do |ta, deps|
    2220:             if deps.empty?
    2221:               dependency_map[ta] = {}
    2222:             else
    2223:               deps = deps.dup
    2224:               hash = dependency_map[deps.shift]
    2225:               deps.each do |dep|
    2226:                 hash = hash[dep]
    2227:               end
    2228:               hash[ta] = {}
    2229:             end
    2230:           end
    2231:
    2232:           # This mapping is used to make sure that duplicate entries in the
    2233:           # result set are mapped to a single record.  For example, using a
    2234:           # single one_to_many association with 10 associated records,
    2235:           # the main object column values appear in the object graph 10 times.
    2236:           # We map by primary key, if available, or by the object's entire values,
    2237:           # if not. The mapping must be per table, so create sub maps for each table
    2238:           # alias.
    2239:           records_map = {@master=>{}}
    2240:           alias_map.keys.each{|ta| records_map[ta] = {}}
    2241:           @records_map = records_map
    2242:
    2243:           datasets = opts[:graph][:table_aliases].to_a.reject{|ta,ds| ds.nil?}
    2244:           column_aliases = opts[:graph_aliases] || opts[:graph][:column_aliases]
    2245:           primary_keys = {}
    2246:           column_maps = {}
    2247:           models = {}
    2248:           row_procs = {}
    2249:           datasets.each do |ta, ds|
    2250:             models[ta] = ds.model
    2251:             primary_keys[ta] = []
    2252:             column_maps[ta] = {}
    2253:             row_procs[ta] = ds.row_proc
    2254:           end
    2255:           column_aliases.each do |col_alias, tc|
    2256:             ta, column = tc
    2257:             column_maps[ta][col_alias] = column
    2258:           end
    2259:           column_maps.each do |ta, h|
    2260:             pk = models[ta].primary_key
    2261:             if pk.is_a?(Array)
    2262:               primary_keys[ta] = []
    2263:               h.select{|ca, c| primary_keys[ta] << ca if pk.include?(c)}
    2264:             else
    2265:               h.select{|ca, c| primary_keys[ta] = ca if pk == c}
    2266:             end
    2267:           end
    2268:           @column_maps = column_maps
    2269:           @primary_keys = primary_keys
    2270:           @row_procs = row_procs
    2271:
    2272:           # For performance, create two special maps for the master table,
    2273:           # so you can skip a hash lookup.
    2274:           @master_column_map = column_maps[master]
    2275:           @master_primary_keys = primary_keys[master]
    2276:
    2277:           # Add a special hash mapping table alias symbols to 5 element arrays that just
    2278:           # contain the data in other data structures for that table alias.  This is
    2279:           # used for performance, to get all values in one hash lookup instead of
    2280:           # separate hash lookups for each data structure.
    2281:           ta_map = {}
    2282:           alias_map.keys.each do |ta|
    2283:             ta_map[ta] = [records_map[ta], row_procs[ta], alias_map[ta], type_map[ta], reciprocal_map[ta]]
    2284:           end
    2285:           @ta_map = ta_map
    2286:         end

### Public Instance methods

load(hashes)

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 2290
    2290:         def load(hashes)
    2291:           master = master()
    2292:
    2293:           # Assign to local variables for speed increase
    2294:           rp = row_procs[master]
    2295:           rm = records_map[master]
    2296:           dm = dependency_map
    2297:
    2298:           # This will hold the final record set that we will be replacing the object graph with.
    2299:           records = []
    2300:
    2301:           hashes.each do |h|
    2302:             unless key = master_pk(h)
    2303:               key = hkey(master_hfor(h))
    2304:             end
    2305:             unless primary_record = rm[key]
    2306:               primary_record = rm[key] = rp.call(master_hfor(h))
    2307:               # Only add it to the list of records to return if it is a new record
    2308:               records.push(primary_record)
    2309:             end
    2310:             # Build all associations for the current object and it's dependencies
    2311:             _load(dm, primary_record, h)
    2312:           end
    2313:
    2314:           # Remove duplicate records from all associations if this graph could possibly be a cartesian product
    2315:           # Run after_load procs if there are any
    2316:           post_process(records, dm) if @unique || !after_load_map.empty? || !limit_map.empty?
    2317:
    2318:           records
    2319:         end

[Validate]