dbt var 简单说明

dbt 的var 可以进行变量的定义以及变量的引用，以下简单说明下

参考使用

引用定义的
参考定义

name: my_dbt_project

version: 1.0.0
 
config-version: 2
 
# Define variables here

vars:

  event_type: activation

select * from events where event_type = '{{ var("event_type") }}'

定义
包含了默认值

select * from events where event_type = '{{ var("event_type", "activation") }}'

{%- set concat_string = var('concat_string', '||') -%}

内部处理

实际上就是一个属性,会包含cli 以及context 中的一些信息

@contextproperty()

def var(self) -> Var:

    """Variables can be passed from your `dbt_project.yml` file into models

    during compilation. These variables are useful for configuring packages

    for deployment in multiple environments, or defining values that should

    be used across multiple models within a package.
 
    To add a variable to a model, use the `var()` function:
 
    > my_model.sql:
 
        select * from events where event_type = '{{ var("event_type") }}'
 
    If you try to run this model without supplying an `event_type`

    variable, you'll receive a compilation error that looks like this:
 
        Encountered an error:

        ! Compilation error while compiling model package_name.my_model:

        ! Required var 'event_type' not found in config:

        Vars supplied to package_name.my_model = {

        }
 
    To supply a variable to a given model, add one or more `vars`

    dictionaries to the `models` config in your `dbt_project.yml` file.

    These `vars` are in-scope for all models at or below where they are

    defined, so place them where they make the most sense. Below are three

    different placements of the `vars` dict, all of which will make the

    `my_model` model compile.
 
    > dbt_project.yml:
 
        # 1) scoped at the model level

        models:

          package_name:

            my_model:

              materialized: view

              vars:

                event_type: activation

        # 2) scoped at the package level

        models:

          package_name:

            vars:

              event_type: activation

            my_model:

              materialized: view

        # 3) scoped globally

        models:

          vars:

            event_type: activation

          package_name:

            my_model:

              materialized: view
 
    ## Variable default values
 
    The `var()` function takes an optional second argument, `default`. If

    this argument is provided, then it will be the default value for the

    variable if one is not explicitly defined.
 
    > my_model.sql:
 
        -- Use 'activation' as the event_type if the variable is not

        -- defined.

        select *

        from events

        where event_type = '{{ var("event_type", "activation") }}'

    """

    return Var(self._ctx, self.cli_vars)