880000 data import and export error memory overflow Postgres SQL ->>MySQL

Describe the problem/error/question

I currently have 880000 pieces of data that need to be imported from Postgres SQL to MySQL. However, I have set up loops and sub workflows according to the community’s methods, but he still reported an error of memory overflow

What is the error message (if any)?

Please share your workflow

“meta”: {
“instanceId”: “c9f2024672e20e625025f74fb3b477b61ffd818e245f44cde9ffba856b2235e0”
“nodes”: [
“parameters”: {
“fromEmail”: “[email protected]”,
“toEmail”: “[email protected]”,
“subject”: “n8n版_抽数完成”,
“emailFormat”: “text”,
“text”: “PG-》mysql完成___本地docker测试环境\n”,
“options”: {}
“id”: “92ca0d3c-8557-46c4-bbe2-9f75c0e08232”,
“name”: “数据抽取完成发送邮件”,
“type”: “n8n-nodes-base.emailSend”,
“typeVersion”: 2.1,
“position”: [
“credentials”: {
“smtp”: {
“id”: “rDDbS5ly4kMh7ETK”,
“name”: “SMTP account”
“connections”: {},
“pinData”: {}

(Select the nodes on your canvas and use the keyboard shortcuts CMD+C/CTRL+C and CMD+V/CTRL+V to copy and paste the workflow.)
  "meta": {
    "instanceId": "c9f2024672e20e625025f74fb3b477b61ffd818e245f44cde9ffba856b2235e0"
  "nodes": [
      "parameters": {
        "fromEmail": "[email protected]",
        "toEmail": "[email protected]",
        "subject": "n8n版_抽数完成",
        "emailFormat": "text",
        "text": "PG-》mysql完成___本地docker测试环境\n",
        "options": {}
      "id": "92ca0d3c-8557-46c4-bbe2-9f75c0e08232",
      "name": "数据抽取完成发送邮件",
      "type": "n8n-nodes-base.emailSend",
      "typeVersion": 2.1,
      "position": [
      "credentials": {
        "smtp": {
          "id": "rDDbS5ly4kMh7ETK",
          "name": "SMTP account"
  "connections": {},
  "pinData": {}

Share the output returned by the last node

My workflow will send an email at the end to remind me that the data has been processed

Information on your n8n setup

  • n8n version: 1.8.2
  • Database (default: SQLite): postgres sql
  • n8n EXECUTIONS_PROCESS setting (default: own, main): main
  • Running n8n via (Docker, npm, n8n cloud, desktop app): Docker
  • Operating system:

Hi @1043038630

Welcome to the community!

It looks like you are retrieving all data in one go, so that would mean you need a lot of memory to get that working.
Best to split it out, as you already do but also with the extraction.
So have it loop and then within that loop grab a part of the data and process it.

1 Like

Thank you very much. I am indeed reading all the data at once. However, I am not sure how to read it in batches? I only know how to write in batches, can you tell me :grinning:

Depends on the data. If you have some kind of ID you can use you can loop through ID ranges. by grabbing the highest and lowest and creating ranges out of that for example.
You should also be able to setup paging by limiting the nr of records and setting an offset, but not sure as I have not tried that.

1 Like

thank you. :grinning: