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CHANGES_BEFORE_V1.md

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Design decisions before v1

This document is a supplement to all the resource changes described in the migration guide on our road to V1 (check the roadmap). Its purpose is to give explanation/context for the decisions spanning multiple resources. It will be updated with more findings/conventions.

Default values

For any resource that went through the rework as part of the resource preparation for V1, the behaviour for default values may change from the previous one.

In the past, the provider copied defaults from Snowflake, creating a tight coupling between them. However, this approach posed a challenge as the defaults on the Snowflake side could change and vary between accounts based on their configurations.

Now, whenever the value is not specified in the configuration, we let the Snowflake fill out the default value for a given field (if there is one). Using such defaults may lead to non-idempotent cases where the same configuration may create a resource with slightly different configuration in Snowflake (depending on the Snowflake Edition and Version, current account configuration, and most-likely other factors). That is why we recommend setting optional fields where you want to ensure that the specified value has been set on the Snowflake side.

Additionally, resources created before this change may experience force replacement plans on boolean fields after upgrading to the new version of the resource. That's because those fields now have different type and default value. The only way to prevent this behavior is to set this value in configuration to the value that was previously in state. Refer to this issue for more details.

Validations

This point connects with the one on about the default values. First of all, we want to reduce the coupling between Snowflake and the provider. Secondly, some of the value limits are soft (consult issues #2948 and #1919) which makes it difficult to align provider validations with the custom setups. Lastly, some values depend on the Snowflake edition used.

Because of all that, we plan to reduce the number of validations (mostly numeric) on the provider side. We won't get rid of them entirely, so that successful plans but apply failures can be limited, but please be aware that you may encounter them.

"Empty" values

The Terraform SDK v2 that is currently used in our provider detects the presence of the attribute based on its non-zero Golang value. This means, that it is not possible to distinguish the removal of the value inside a config from setting it explicitely to a zero value, e.g. 0 for the numeric value (check this thread). Before we migrate to the new recommended Terraform Plugin Framework we want to handle such cases the same way inside the provider. It means that:

  • boolean attributes will be migrated to the string attributes with two values: "true" and "false" settable in the config and the special third value "default" that will mean, that the given attribute is not set inside the config.
  • integer values with the possible 0 value in Snowflake (e.g. AUTO_SUSPEND in warehouse) will have a special default (usually a -1) assigned on the provider side when the config is left empty for them.
  • string values with the possible empty ("") value (e.g. default for column value in a table) will have a special default "<Snowflake Terraform Provider string default>" that will be used for the empty config. It won't be possible to use the above values directly (it will be for the string attributes) but users should be aware of them, because they may appear in the terraform plans.

Snowflake parameters

Snowflake parameters have different types and hierarchies. In the earlier versions of the provider they have been handled non-intuitively by setting the deault values inside the provider (e.g. #2356). We want to change that. Because of that we decided to:

  • make all parameters available for the given object available in the resource (without the need to use the snowflake_object_parameter resource which future will be discussed in the next few weeks; for the V1 ready resources, you should not use snowflake_<object> and snowflake_object_parameter together: if you manage <object> through terraform, and you want to set the parameter on the object's level, it must be done in snowflake_<object> resource)
  • remove the default values from Snowflake parameters in every resource before the V1. This is an important breaking change. In the previous versions usually not setting the given parameter resulted in using the provider default. This was different from creating the same object without the parameter by hand (because Snowflake just takes the parameter from the hierarchy in such case).
  • provider will identify both the internal and the external changes to these parameters on both value and level levels, e.g.:
    • setting the parameter inside the config and then manually unsetting it to the same value on the higher level will result in detecting a change
    • not setting the parameter inside the config and then manually changing the parameter on object level to the same value as the value one level higher in the hierarchy will result in detecting a change
  • handle parameters as optional/computed values in the provider
  • add, in all objects having at least one parameter, a special computed collection parameters containing all the values and levels of parameters (the result of SHOW PARAMETERS IN <object> <name>).

Config values in the state

Currently, not setting a value for the given attribute inside the config results in populating this field in state with the value extracted from Snowflake (usually by running SHOW/DESCRIBE). This poses a challenge to identify if the change happened externally or is it just a default Snowflake value (multiple issues reported describe the issue with the infinite plans or weird drifts - this is one of the main reasons). With getting rid of the Snowflake defaults from the provider, it's not an easy thing to do in the currently used Terraform SDK v2. We have considered and tested a variety of options, including custom diff suppression, setting these fields as optional and computed, and others, but there were smaller or bigger problems with these approaches. What we ended up with, and what will be a guideline for the V1 is:

  • we do not fill the given attribute in the state if it is not present inside a config (for the optional attributes; the required ones are always present)
  • we encourage to always use the value directly if you don't want to depend on the Snowflake default (consult default values section)
  • this may result in change detection with migrations to the newer versions of the provider (because currently, the value is stored independently of being present in the config or not and there is no way to deduce its presence in the automatic state migrations we can provide) - alternative would be to follow our resource migration guide
  • we will provide a show_output and describe_output in each resource (more in Raw Snowflake output section)

Raw Snowflake output

Because of the changes regarding Config values in the state we want to still allow our users to get the value of the given attribute, even when it is not set in the config. For each resource (and datasource) we will provide:

  • show_output computed field, containing the response of SHOW <object> for the given managed object
  • describe_output computed field, containing the response of DESCRIBE <object> <name> for the given managed object
  • parameters computed field, containing all the values and levels of Snowflake parameters (the result of SHOW PARAMETERS IN <object> <name>)

This way, it is still possible to obtain the values in your configs, even without setting them directly for the given managed object.

Object cloning

Some of the Snowflake objects (like Database) can create clones from already existing objects. For now, we decided to drop the support for object cloning. That's why during the resource preparation for V1 we will be removing the option to clone (if they exist in the current implementation). The main reasons behind that decision are

  • With object cloning we have to keep in mind additional things that still have to be researched to check how they're matching within the Terraform ecosystem.
  • There is potentially not enough information in Snowflake available for the end users (like us) to track the information about the connection between cloned objects.
  • There are still at least a few of the design decisions that have to be answered before knowingly putting cloning into resources

Because of that, we would like to shelve the idea of introducing cloning to the resources (at least for V1). After V1, object cloning is one of the topics we would like to take a closer look at. Right now, the cloning can be done manually and imported into normal resources, but in case there is any divergence between the normal and cloned object, the resources may act in an unexpected way. An alternative solution is to use plain SQL with unsafe execute resources for now.

Identifier design decisions

The summary of design decisions taken during the identifiers rework was put into a separate document (here).