Debounce writing updated parent node

Author: KyleAMathews

packages/gatsby/src/datastore/lmdb/lmdb-datastore.ts

@@ -7,6 +7,7 @@ import { IDataStore, ILmdbDatabases, IQueryResult } from "../types"
 import { emitter, replaceReducer } from "../../redux"
 import { GatsbyIterable } from "../common/iterable"
 import { doRunQuery } from "./query/run-query"
+import _ from "lodash"
 import {
   IRunFilterArg,
   runFastFiltersAndSort,
@@ -219,6 +220,8 @@ async function runQuery(args: IRunFilterArg): Promise<IQueryResult> {
 
 let lastOperationPromise: Promise<any> = Promise.resolve()
 
+const debounceFunctionsPerNode = new Map()
+
 function updateDataStore(action: ActionsUnion): void {
   switch (action.type) {
     case `DELETE_CACHE`: {
@@ -237,10 +240,26 @@ function updateDataStore(action: ActionsUnion): void {
       clearIndexes()
       break
     }
+    case `ADD_CHILD_NODE_TO_PARENT_NODE`: {
+      let fn
+      const dbs = getDatabases()
+      if (!debounceFunctionsPerNode.has(action.payload.id)) {
+        fn = _.debounce(_action => {
+          updateNodes(dbs.nodes, _action)
+          updateNodesByType(dbs.nodesByType, _action)
+        }, 1000)
+        debounceFunctionsPerNode.set(action.payload.id, fn)
+      } else {
+        fn = debounceFunctionsPerNode.get(action.payload.id)
+      }
+
+      // Call the debounce function.
+      fn(action)
+      break
+    }
     case `CREATE_NODE`:
     case `DELETE_NODE`:
     case `ADD_FIELD_TO_NODE`:
-    case `ADD_CHILD_NODE_TO_PARENT_NODE`:
     case `MATERIALIZE_PAGE_MODE`: {
       const dbs = getDatabases()
       const operationPromise = Promise.all([