azurerm_mssql_elasticpool license_type can't be set to null when changing from vCore to DTU model

[reschex]

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Terraform Version

1.5.0

AzureRM Provider Version

3.62.1

Affected Resource(s)/Data Source(s)

azurerm_mssql_elasticpool

Terraform Configuration Files

variable "db_performance_tier" {
  type        = string
  default     = ""
}

resource "azurerm_resource_group" "this" {
  name     = "resourcepool_test"
  location = "West Europe"

}

resource "azurerm_mssql_server" "this" {
  name                         = azurerm_resource_group.this.name
  resource_group_name          = azurerm_resource_group.this.name
  location                     = azurerm_resource_group.this.location
  version                      = "12.0"
  administrator_login          = "sql_admin"
  administrator_login_password = "YOUR PASSWORD HERE"
  minimum_tls_version          = "1.2"
}

locals {
  db_performance_tiers = {
    default = {
      tier     = "Standard"
      name     = "StandardPool"
      license_type = null
      capacity = 50
      min_capacity = 10
    }
    high = {
      tier     = "GeneralPurpose"
      name     = "GP_Gen5"
      family   = "Gen5"
      license_type = "LicenseIncluded"
      capacity = 6
      min_capacity = 0.25
    }
  }

  db_performance_tier = merge(local.db_performance_tiers.default, lookup(local.db_performance_tiers, var.db_performance_tier, local.db_performance_tiers.default))

}

resource "azurerm_mssql_elasticpool" "this" {
  name                = azurerm_resource_group.this.name
  resource_group_name = azurerm_resource_group.this.name
  location            = azurerm_resource_group.this.location
  server_name         = azurerm_mssql_server.this.name
  license_type        = local.db_performance_tier.license_type
  max_size_gb         = 5

  sku {
    name     = local.db_performance_tier.name
    tier     = local.db_performance_tier.tier
    family   = contains(keys(local.db_performance_tier), "family") ? local.db_performance_tier.family : null
    capacity = local.db_performance_tier.capacity
  }

  per_database_settings {
    min_capacity = local.db_performance_tier.min_capacity
    max_capacity = local.db_performance_tier.capacity
  }
}

Debug Output/Panic Output

Error: `license_type` can only be configured when `sku.0.tier` is set to `GeneralPurpose` or `BusinessCritical`

Expected Behaviour

when changing the var db_performance_tier from "high" to "", the pool should get downgraded from vCore model to eDTU model.

Actual Behaviour

terraform apply fails with this error:

Error: `license_type` can only be configured when `sku.0.tier` is set to `GeneralPurpose` or `BusinessCritical`

the plan doesn't show the license_type parameter being changed back to null:

Terraform will perform the following actions:

  # module.sql_server.azurerm_mssql_elasticpool.this will be updated in-place
  ~ resource "azurerm_mssql_elasticpool" "this" {
        id                             = "XXXX"
        name                           = "XXXX"
        tags                           = {}
        # (8 unchanged attributes hidden)

      ~ per_database_settings {
          ~ max_capacity = 6 -> 50
          ~ min_capacity = 0.25 -> 10
        }

      ~ sku {
          ~ capacity = 6 -> 50
          - family   = "Gen5" -> null
          ~ name     = "GP_Gen5" -> "StandardPool"
          ~ tier     = "GeneralPurpose" -> "Standard"
        }
    }

Plan: 0 to add, 1 to change, 0 to destroy.

Steps to Reproduce

terraform apply with the var.db_performance_tier set to ""
terraform apply with the var.db_performance_tier set to "high"
terraform apply with the var.db_performance_tier set back to ""

Important Factoids

No response

References

No response

[rcskosir]

@reschex Thank you for taking the time to open this issue. Please subscribe to PR #23262 that @sinbai has opened related to this issue.

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