Merge pull request #53 from fishtown-analytics/feature/surrogate-key

Feature/surrogate key

README.md

@@ -186,6 +186,14 @@ Usage:
 {{ dbt_utils.generate_series(upper_bound=1000) }}
 ```
 
+#### surrogate_key ([source](macros/sql/surrogate_key.sql))
+Implements a cross-database way to generate a hashed surrogate key using the fields specified.
+
+Usage:
+```
+{{ dbt_utils.surrogate_key('field_a', 'field_b'[,...]) }}
+```
+
 #### pivot ([source](macros/sql/pivot.sql))
 This macro pivots values from rows to columns.
 

macros/cross_db_utils/concat.sql

@@ -0,0 +1,23 @@
+{% macro concat(fields) %}
+  {{ adapter_macro('dbt_utils.concat', fields) }}
+{% endmacro %}
+
+
+{% macro default__concat(fields) -%}
+    concat({{ fields|join(', ') }})
+{%- endmacro %}
+
+
+{% macro alternative_concat(fields) %}
+    {{ fields|join(' || ') }}
+{% endmacro %}
+
+
+{% macro redshift__concat(fields) %}
+    {{dbt_utils.alternative_concat(fields)}}
+{% endmacro %}
+
+
+{% macro snowflake__concat(fields) %}
+    {{dbt_utils.alternative_concat(fields)}}
+{% endmacro %}

macros/cross_db_utils/datatypes.sql

@@ -0,0 +1,21 @@
+{# string  -------------------------------------------------     #}
+
+{% macro type_string() %}
+  {{ adapter_macro('dbt_utils.type_string') }}
+{% endmacro %}
+
+{% macro default__type_string() %}
+    string
+{% endmacro %}
+
+{%- macro redshift__type_string() -%}
+    varchar
+{%- endmacro -%}
+
+{% macro postgres__type_string() %}
+    varchar
+{% endmacro %}
+
+{% macro snowflake__type_string() %}
+    varchar
+{% endmacro %}

macros/cross_db_utils/safe_cast.sql

@@ -0,0 +1,20 @@
+{% macro safe_cast(field, type) %}
+  {{ adapter_macro('dbt_utils.safe_cast', field, type) }}
+{% endmacro %}
+
+
+{% macro default__safe_cast(field, type) %}
+    {# most databases don't support this function yet
+    so we just need to use cast #}
+    cast({{field}} as {{type}})
+{% endmacro %}
+
+
+{% macro snowflake__safe_cast(field, type) %}
+    try_cast({{field}} as {{type}})
+{% endmacro %}
+
+
+{% macro bigquery__safe_cast(field, type) %}
+    safe_cast({{field}} as {{type}})
+{% endmacro %}

macros/sql/surrogate_key.sql

@@ -0,0 +1,19 @@
+{%- macro surrogate_key() -%}
+
+{% set fields = [] %}
+
+{%- for field in varargs -%}
+
+    {% set _ = fields.append(
+        "coalesce(cast(" ~ field ~ " as " ~ dbt_utils.type_string() ~ "), '')"
+    ) %}
+
+    {% if not loop.last %}
+        {% set _ = fields.append("'-'") %}
+    {% endif %}
+
+{%- endfor -%}
+
+md5({{dbt_utils.concat(fields)}})
+
+{%- endmacro -%}