Closed
Description
What happened
Set has an extra map((_, k) => k) transformation in implementation of __iterator(). It causes reify() to recreate the whole collection from scratch.
__iterator(type, reverse) {
return this._map.map((_, k) => k).__iterator(type, reverse);
}It is noticeable on sets with higher number of items.
In our fork https://github.com/applitopia/immutable-sorted we fixed it by changing the add() function as follows:
add(value) {
- return updateSet(this, this._map.set(value, true));
+ return updateSet(this, this._map.set(value, value));
}How to reproduce
const { Set, Map, Range } = require('immutable');
const time = function(s, f) {
const ts1 = Date.now();
f();
const ts2 = Date.now();
const tm = Math.floor(ts2-ts1)/1000;
console.log("%s: %ds", s, tm);
};
time("Set", ()=>Range(0,1000000).toSet());
time("Set+__iterator", ()=>Range(0,1000000).toSet().__iterator());
time("Map", ()=>Range(0,1000000).toKeyedSeq().toMap());
time("Map+__iterator", ()=>Range(0,1000000).toKeyedSeq().toMap().__iterator());Output:
Set: 0.777s
Set+__iterator: 1.343s
Map: 0.611s
Map+__iterator: 0.55s
The time needed for Set+__iterator has doubled.