Add deduplication macro (#512)

* Update README.md

* Mutually excl range examples in disclosure triangle

* Fix union_relations error when no include/exclude provided

* Fix union_relations error when no include/exclude provided (#509)

* Update CHANGELOG.md

* Add dedupe macro

* Add test for dedupe macro

* Add documentation to README

* Add entry to CHANGELOG

* Implement review

CHANGELOG.md

@@ -1,3 +1,7 @@
+# dbt-utils v0.8.3
+## New features
+- A macro for deduplicating data ([#335](https://github.com/dbt-labs/dbt-utils/issues/335), [#512](https://github.com/dbt-labs/dbt-utils/pull/512))
+
 # dbt-utils v0.8.2
 ## Fixes
 - Fix union_relations error from [#473](https://github.com/dbt-labs/dbt-utils/pull/473) when no include/exclude parameters are provided ([#505](https://github.com/dbt-labs/dbt-utils/issues/505), [#509](https://github.com/dbt-labs/dbt-utils/pull/509))
@@ -32,7 +36,7 @@
 
 # dbt-utils v0.8.0
 ## 🚨 Breaking changes
-- dbt ONE POINT OH is here! This version of dbt-utils requires _any_ version (minor and patch) of v1, which means far less need for compatibility releases in the future. 
+- dbt ONE POINT OH is here! This version of dbt-utils requires _any_ version (minor and patch) of v1, which means far less need for compatibility releases in the future.
 - The partition column in the `mutually_exclusive_ranges` test is now always called `partition_by_col`. This enables compatibility with `--store-failures` when multiple columns are concatenated together. If you have models built on top of the failures table, update them to reflect the new column name. ([#423](https://github.com/dbt-labs/dbt-utils/issues/423), [#430](https://github.com/dbt-labs/dbt-utils/pull/430))
 
 ## Contributors:

README.md

@@ -36,6 +36,7 @@ For compatibility details between versions of dbt-core and dbt-utils, [see this
 
 - [SQL generators](#sql-generators)
     - [date_spine](#date_spine-source)
+    - [dedupe](#dedupe-source)
     - [haversine_distance](#haversine_distance-source)
     - [group_by](#group_by-source)
     - [star](#star-source)
@@ -706,6 +707,20 @@ This macro returns the sql required to build a date spine. The spine will includ
 }}
 ```
 
+#### deduplicate ([source](macros/sql/deduplicate.sql))
+This macro returns the sql required to remove duplicate rows from a model or source.
+
+**Usage:**
+
+```
+{{ dbt_utils.deduplicate(
+    relation=source('my_source', 'my_table'),
+    group_by="user_id, cast(timestamp as day)",
+    order_by="timestamp desc"
+   )
+}}
+```
+
 #### haversine_distance ([source](macros/sql/haversine_distance.sql))
 This macro calculates the [haversine distance](http://daynebatten.com/2015/09/latitude-longitude-distance-sql/) between a pair of x/y coordinates.
 
@@ -748,7 +763,7 @@ group by 1,2,3
 ```
 
 #### star ([source](macros/sql/star.sql))
-This macro generates a comma-separated list of all fields that exist in the `from` relation, excluding any fields listed in the `except` argument. The construction is identical to `select * from {{ref('my_model')}}`, replacing star (`*`) with the star macro. This macro also has an optional `relation_alias` argument that will prefix all generated fields with an alias (`relation_alias`.`field_name`). 
+This macro generates a comma-separated list of all fields that exist in the `from` relation, excluding any fields listed in the `except` argument. The construction is identical to `select * from {{ref('my_model')}}`, replacing star (`*`) with the star macro. This macro also has an optional `relation_alias` argument that will prefix all generated fields with an alias (`relation_alias`.`field_name`).
 
 The macro also has optional `prefix` and `suffix` arguments. When one or both are provided, they will be concatenated onto each field's alias in the output (`prefix` ~ `field_name` ~ `suffix`). NB: This prevents the output from being used in any context other than a select statement.
 

integration_tests/data/sql/data_deduplicate.csv

@@ -0,0 +1,3 @@
+user_id,event,version
+1,play,1
+1,play,2

integration_tests/data/sql/data_deduplicate_expected.csv

@@ -0,0 +1,2 @@
+user_id,event,version
+1,play,2

integration_tests/models/sql/schema.yml

@@ -85,7 +85,7 @@ models:
     tests:
       - dbt_utils.equality:
           compare_model: ref('data_pivot_expected')
-  
+
   - name: test_pivot_apostrophe
     tests:
       - dbt_utils.equality:
@@ -137,8 +137,13 @@ models:
     tests:
       - dbt_utils.equality:
           compare_model: ref('data_union_expected')
-          
+
   - name: test_get_relations_by_pattern
     tests:
       - dbt_utils.equality:
           compare_model: ref('data_union_events_expected')
+
+  - name: test_dedupe
+    tests:
+      - dbt_utils.equality:
+          compare_model: ref('data_deduplicate_expected')

integration_tests/models/sql/test_deduplicate.sql

@@ -0,0 +1,7 @@
+with deduped as (
+
+    {{ dbt_utils.deduplicate(ref('data_deduplicate'), group_by='user_id', order_by='version desc') | indent }}
+
+)
+
+select * from deduped

macros/sql/deduplicate.sql

@@ -0,0 +1,46 @@
+{%- macro deduplicate(relation, group_by, order_by=none) -%}
+    {{ return(adapter.dispatch('deduplicate', 'dbt_utils')(relation, group_by, order_by=order_by)) }}
+{% endmacro %}
+
+{%- macro default__deduplicate(relation, group_by, order_by=none) -%}
+
+    select
+        {{ dbt_utils.star(relation, relation_alias='deduped') | indent }}
+    from (
+        select
+            _inner.*,
+            row_number() over (
+                partition by {{ group_by }}
+                {% if order_by is not none -%}
+                order by {{ order_by }}
+                {%- endif %}
+            ) as rn
+        from {{ relation }} as _inner
+    ) as deduped
+    where deduped.rn = 1
+
+{%- endmacro -%}
+
+{#
+--  It is more performant to deduplicate using `array_agg` with a limit
+--  clause in BigQuery:
+--  https://github.com/dbt-labs/dbt-utils/issues/335#issuecomment-788157572
+#}
+{%- macro bigquery__deduplicate(relation, group_by, order_by=none) -%}
+
+    select
+        {{ dbt_utils.star(relation, relation_alias='deduped') | indent }}
+    from (
+        select
+            array_agg (
+                original
+                {% if order_by is not none -%}
+                order by {{ order_by }}
+                {%- endif %}
+                limit 1
+            )[offset(0)] as deduped
+        from {{ relation }} as original
+        group by {{ group_by }}
+    )
+
+{%- endmacro -%}