Postgres jsonb expects json valid

[brunorafaeI]

Bug Description

I'm trying to inser data into a jsonb column (Postgres 17), but the Postgres node returns an error, saying that an object is expected but array of objetc is given. However, the array of objects is a valid JSON, and the postgres database itself accepts the insertion of it, so it doesn't make sense for the node to block the insertion of this data. This would prevent the need to create a loop of inserts to insert each objet.

To Reproduce

1. Give a array json to insert in database (column jsonb)

Expected behavior

Insert array of object normally, let the database decide to insert or not .

Debug Info

Debug info

core

• n8nVersion: 1.108.1
• platform: docker (self-hosted)
• nodeJsVersion: 22.17.0
• database: sqlite
• executionMode: regular
• concurrency: -1
• license: enterprise (production)
• consumerId: b66c1ef0-ac3e-4965-9287-f9746c8bbd0f

storage

• success: all
• error: all
• progress: false
• manual: true
• binaryMode: memory

pruning

• enabled: true
• maxAge: 336 hours
• maxCount: 10000 executions

client

• userAgent: mozilla/5.0 (windows nt 10.0; win64; x64) applewebkit/537.36 (khtml, like gecko) chrome/138.0.0.0 safari/537.36
• isTouchDevice: false

Generated at: 2025-08-27T16:43:13.278Z

Operating System

Debian 12 (bookworm)

n8n Version

1.108.1

Node.js Version

22.17.0

Database

PostgreSQL

Execution mode

main (default)

Hosting

self hosted

[adii2327]

Potential workarounds:

Convert the JSON array to a string before passing it into the Postgres node (use JSON.stringify()), but you mentioned that didn't work.

Change the column type to plain jsonb (if it is not already), not jsonb[], so the whole array of objects is treated as one JSONB object.

Insert the JSON array as a parameter using a native query or use parameterized queries directly with the node to bypass format checking.

If using ORM or query builder, ensure the JSON is serialized correctly and passed as a single JSONB parameter.

If n8n node behavior restricts this, consider opening a feature request or bug report if it does not allow valid JSON array insertion directly.

[Joffcom]

Hey @brunorafaeI,

Thank you for reaching out! We’ve received your issue and are looking into it. To help us track this internally, we’ve created a Linear ticket with the reference: "GHC-4076".

We’ll keep you updated as we make progress, but if you have any additional details or context to share, feel free to add them here - it’s always helpful!

Thanks for your patience and for bringing this to our attention.

[brunorafaeI]

Potential workarounds:

Convert the JSON array to a string before passing it into the Postgres node (use JSON.stringify()), but you mentioned that didn't work.

Change the column type to plain jsonb (if it is not already), not jsonb[], so the whole array of objects is treated as one JSONB object.

Insert the JSON array as a parameter using a native query or use parameterized queries directly with the node to bypass format checking.

If using ORM or query builder, ensure the JSON is serialized correctly and passed as a single JSONB parameter.

If n8n node behavior restricts this, consider opening a feature request or bug report if it does not allow valid JSON array insertion directly.

@adii2327
Thank you for your response. The problem lies in the Postgres node of n8n and not in the database. I am being forced to create a script that can insert data from a JSON file; it is working, but the correct approach would be to fix the Postgres node in n8n so that it accepts the array as a data type being passed to a column of type json/jsonb. There is no jsonb[], only json/jsonb. The difference between the two is that one will be treated as binary and the other as text by the Postgres engine.

If n8n node behavior restricts this, consider opening a feature request or bug report if it does not allow valid JSON array insertion directly.

That's exactly what I'm doing here.

[brunorafaeI]

I was poking around in the n8n code and noticed that support for the 'json' type already exists in the code, so there should be the same for 'jsonb'. I believe it would be appropriate to adapt this part of the code:

to

['json', 'jsonb'].includes(data_type)  // or
data_type === 'json' || data_type === 'jsonb'

In this way, the code would not define the field as type 'collection', returning an error for a valid JSON format like an array of objects that is accepted by teh PostgreSQL database.

[luizeof]

@Joffcom same here... Supabase JSONB (with or without Array Option)

Error message:

column "itens" is of type jsonb but expression is of type text[]
You will need to rewrite or cast the expression.

[citizenfish]

I'm having the same issue as @luizeof but in Postgres:-

This fails on a jsonb column

["foo", "baa"]

This works:

{
  "tags" : ["foo", "baa"]
}

I had to use a custom query postgres node with parameters:-

INSERT INTO blogs(slug, location, geom, content, tags, title)
SELECT $1,
       $2,
       $3::GEOMETRY,
       $4,
       $5::JSONB,
       $6
    
ON CONFLICT (slug)
DO UPDATE 
SET location=$2,
geom = $3::GEOMETRY,
content = $4 ,
tags = $5::JSONB,
title=$6
RETURNING ID

Pass tags in as a parameter as follows:-

 JSON.stringify([$('Webhook').first().json.body.blog_theme,$('Webhook').first().json.body.area_name])

[ckenna]

I have the same issue in that any incoming data I have in the Postgres node that is an array requires me to work around the n8n validator. Specifically, in my case, I have this as an input:

{{ $json.lineItems }} is [Array: [{"sku": "$_SERVICE_fdc5802baff9fbc", "description": "blah blah", "quantity": 1, "price": 140, "total": 140, "taxAmount": 0, "discountAmount": 0},...]]

I get the same validation error 'line_items' expects a object but we got array.

An (annoying) work around is to use {{ { items: $json.lineItems } }} which will unnecessarily wrap the array in the object with the items field.

I suppose I can also try a custom query.

[Nyrest]

jsonb accepts primitive js data types and absolutely not just an object, this limitation is totally pointless.
For now, we only have two workarounds:

1. Use query node to run custom sql
2. Wrap an object
   Hope this problem could be fixed ASAP

[davidpanic]

Can this please get fixed, we have tons of jsonb columns with arrays inside of them and we simply cannot insert into them currently using n8n without resorting to custom queries.

[Fylipp]

We make use of a lot of the JSON-related features in PostgreSQL and this bug makes integration painful.

This is a case of n8n rejecting a column value that the database will happily accept. PostgreSQL's JSONB columns explicitly support arrays (and also primitives!) without an enclosing object.

The official documentation itself recommends using JSONB for most applications. Advantages of JSONB over JSON include more efficient queries and support for indexing.