improve memory allocation ⇒ less "minor gc" cleanups

src/utils/Transaction.js

@@ -1,7 +1,6 @@
 
 import {
   getState,
-  createID,
   writeStructsFromTransaction,
   writeDeleteSet,
   DeleteSet,
@@ -11,7 +10,8 @@ import {
   callEventHandlerListeners,
   Item,
   generateNewClientId,
-  StructStore, ID, AbstractType, AbstractStruct, YEvent, Doc // eslint-disable-line
+  createID,
+  GC, StructStore, ID, AbstractType, AbstractStruct, YEvent, Doc // eslint-disable-line
 } from '../internals.js'
 
 import * as encoding from 'lib0/encoding.js'
@@ -86,9 +86,9 @@ export class Transaction {
      */
     this.changedParentTypes = new Map()
     /**
-     * @type {Set<ID>}
+     * @type {Array<AbstractStruct>}
      */
-    this._mergeStructs = new Set()
+    this._mergeStructs = []
     /**
      * @type {any}
      */
@@ -170,7 +170,7 @@ const tryToMergeWithLeft = (structs, pos) => {
  */
 const tryGcDeleteSet = (ds, store, gcFilter) => {
   for (const [client, deleteItems] of ds.clients) {
-    const structs = /** @type {Array<AbstractStruct>} */ (store.clients.get(client))
+    const structs = /** @type {Array<GC|Item>} */ (store.clients.get(client))
     for (let di = deleteItems.length - 1; di >= 0; di--) {
       const deleteItem = deleteItems[di]
       const endDeleteItemClock = deleteItem.clock + deleteItem.len
@@ -199,7 +199,7 @@ const tryMergeDeleteSet = (ds, store) => {
   // try to merge deleted / gc'd items
   // merge from right to left for better efficiecy and so we don't miss any merge targets
   for (const [client, deleteItems] of ds.clients) {
-    const structs = /** @type {Array<AbstractStruct>} */ (store.clients.get(client))
+    const structs = /** @type {Array<GC|Item>} */ (store.clients.get(client))
     for (let di = deleteItems.length - 1; di >= 0; di--) {
       const deleteItem = deleteItems[di]
       // start with merging the item next to the last deleted item
@@ -235,6 +235,7 @@ const cleanupTransactions = (transactionCleanups, i) => {
     const doc = transaction.doc
     const store = doc.store
     const ds = transaction.deleteSet
+    const mergeStructs = transaction._mergeStructs
     try {
       sortAndMergeDeleteSet(ds)
       transaction.afterState = getStateVector(transaction.doc.store)
@@ -292,7 +293,7 @@ const cleanupTransactions = (transactionCleanups, i) => {
       for (const [client, clock] of transaction.afterState) {
         const beforeClock = transaction.beforeState.get(client) || 0
         if (beforeClock !== clock) {
-          const structs = /** @type {Array<AbstractStruct>} */ (store.clients.get(client))
+          const structs = /** @type {Array<GC|Item>} */ (store.clients.get(client))
           // we iterate from right to left so we can safely remove entries
           const firstChangePos = math.max(findIndexSS(structs, beforeClock), 1)
           for (let i = structs.length - 1; i >= firstChangePos; i--) {
@@ -303,10 +304,9 @@ const cleanupTransactions = (transactionCleanups, i) => {
       // try to merge mergeStructs
       // @todo: it makes more sense to transform mergeStructs to a DS, sort it, and merge from right to left
       //        but at the moment DS does not handle duplicates
-      for (const mid of transaction._mergeStructs) {
-        const client = mid.client
-        const clock = mid.clock
-        const structs = /** @type {Array<AbstractStruct>} */ (store.clients.get(client))
+      for (let i = 0; i < mergeStructs.length; i++) {
+        const { client, clock } = mergeStructs[i].id
+        const structs = /** @type {Array<GC|Item>} */ (store.clients.get(client))
         const replacedStructPos = findIndexSS(structs, clock)
         if (replacedStructPos + 1 < structs.length) {
           tryToMergeWithLeft(structs, replacedStructPos + 1)