perf: make stable object shapes

Author: nigrosimone

packages/pg/lib/deque.js

@@ -12,7 +12,14 @@ class Deque {
   shift() {
     if (this._head === this._tail) return undefined
     const item = this._store[this._head]
-    delete this._store[this._head++]
+    this._store[this._head] = undefined
+    this._head++
+
+    if (this._head === this._tail) {
+      this._head = 0
+      this._tail = 0
+    }
+
     return item
   }
 
@@ -27,23 +34,33 @@ class Deque {
   }
 
   remove(item) {
-    const newStore = Object.create(null)
-    const newHead = 0
-    let newTail = 0
-    for (let i = this._head; i < this._tail; i++) {
-      const current = this._store[i]
+    if (this._head === this._tail) return
+
+    const store = this._store
+    let write = this._head
+
+    for (let read = this._head; read < this._tail; read++) {
+      const current = store[read]
       if (current !== item) {
-        newStore[newTail++] = current
+        store[write++] = current
       }
     }
-    this._store = newStore
-    this._head = newHead
-    this._tail = newTail
+
+    for (let i = write; i < this._tail; i++) {
+      store[i] = undefined
+    }
+
+    this._tail = write
+
+    if (this._head === this._tail) {
+      this._head = 0
+      this._tail = 0
+    }
   }
 
   forEach(fn) {
     for (let i = this._head; i < this._tail; i++) {
-      fn(this._store[i], i)
+      fn(this._store[i])
     }
   }
 }