Changing hash_key with Terraform causes Table already exists error

Question

I have a DynamoDB table created with this Terraform:

resource "aws_dynamodb_table" "materials_table" {
  name              = "materials"
  hash_key          = "MATERIAL"
  billing_mode      = "PROVISIONED"
  read_capacity     = 5
  write_capacity    = 5
  
  attribute {
    name = "MATERIAL"
    type = "S"
  }
}

The table was successfully populated (with 4 records, as noted in this post) but in order to solve the problem (in that post) I have added a field PK and set that as the hash_key field, with this:

resource "aws_dynamodb_table" "materials_table" {
  name              = "materials"
  hash_key          = "PK"
  billing_mode      = "PROVISIONED"
  read_capacity     = 5
  write_capacity    = 5
  
  attribute {
    name = "PK"
    type = "S"
  }
}

This has caused the following error, when running terraform apply:

Error: error creating DynamoDB Table: ResourceInUseException: Table already exists: materials

What do I need to do in the .tf to get the change accepted?

Balu Vyamajala · Accepted Answer · 2021-02-26T14:58:25.823

3

Changing some of the attributes in DynamoDB is not permitted, for example, changing Partition key, adding a Local Secondary Index, etc.

When such changes occur, it will need to replace the resource and to replace, it will try to delete and re-create the resource. During this process, if table already exists, it will fail.

Only option is to delete the stack or manually delete the DynamoDB Table and let template create it again. Or Renaming the table.

Documentation says it will force new resource

hash_key - (Required, Forces new resource) The attribute to use as the hash (partition) key.

edited Feb 26 '21 at 14:58

answered Feb 26 '21 at 14:43

Balu Vyamajala

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I'm using Terraform, not CloudFormation. – Matt W Feb 26 '21 at 14:45
I was expecting the table to be deleted, but the error implies this is not being attempted. – Matt W Feb 26 '21 at 14:46
I think, it will first try to create the table and then delete it. – Balu Vyamajala Feb 26 '21 at 14:47
So renaming the table should help delete it..? – Matt W Feb 26 '21 at 14:50
1

100% . renaming will surely help. – Balu Vyamajala Feb 26 '21 at 14:51
I saw that the docs say "forces new resource" and thought this would do exactly that. I guess it's the process it uses to get there which failed. – Matt W Feb 26 '21 at 15:00

Changing hash_key with Terraform causes Table already exists error

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