From 6a29323add80cbb1beb0e20beb14d69c742ec576 Mon Sep 17 00:00:00 2001
From: Dan M <47741043+dmarts@users.noreply.github.com>
Date: Wed, 13 May 2020 15:09:25 +0100
Subject: [PATCH 1/2] Macro and test case

---
 README.md                                     | 13 +++++++
 .../data_test_fewer_rows_than_table_1.csv     |  4 +++
 .../data_test_fewer_rows_than_table_2.csv     |  5 +++
 .../schema_tests/test_fewer_rows_than.sql     |  9 +++++
 macros/schema_tests/fewer_rows_than.sql       | 35 +++++++++++++++++++
 5 files changed, 66 insertions(+)
 create mode 100644 integration_tests/data/schema_tests/data_test_fewer_rows_than_table_1.csv
 create mode 100644 integration_tests/data/schema_tests/data_test_fewer_rows_than_table_2.csv
 create mode 100644 integration_tests/models/schema_tests/test_fewer_rows_than.sql
 create mode 100644 macros/schema_tests/fewer_rows_than.sql

diff --git a/README.md b/README.md
index 9f5afcfa..d86dbf8d 100644
--- a/README.md
+++ b/README.md
@@ -132,6 +132,19 @@ models:
 
 ```
 
+#### fewer_rows_than ([source](macros/schema_tests/fewer_rows_than.sql))
+This schema test asserts that this model has fewer rows than the referenced model.
+
+Usage:
+```yaml
+version: 2
+
+models:
+  - name: model_name
+    tests:
+      - dbt_utils.fewer_rows_than:
+          compare_model: ref('other_table_name')
+
 #### equality ([source](macros/schema_tests/equality.sql))
 This schema test asserts the equality of two relations. Optionally specify a subset of columns to compare.
 
diff --git a/integration_tests/data/schema_tests/data_test_fewer_rows_than_table_1.csv b/integration_tests/data/schema_tests/data_test_fewer_rows_than_table_1.csv
new file mode 100644
index 00000000..ba0e5ec6
--- /dev/null
+++ b/integration_tests/data/schema_tests/data_test_fewer_rows_than_table_1.csv
@@ -0,0 +1,4 @@
+field
+1
+2
+3
diff --git a/integration_tests/data/schema_tests/data_test_fewer_rows_than_table_2.csv b/integration_tests/data/schema_tests/data_test_fewer_rows_than_table_2.csv
new file mode 100644
index 00000000..eb0f035a
--- /dev/null
+++ b/integration_tests/data/schema_tests/data_test_fewer_rows_than_table_2.csv
@@ -0,0 +1,5 @@
+field
+1
+2
+3
+4
diff --git a/integration_tests/models/schema_tests/test_fewer_rows_than.sql b/integration_tests/models/schema_tests/test_fewer_rows_than.sql
new file mode 100644
index 00000000..c2ad4cbd
--- /dev/null
+++ b/integration_tests/models/schema_tests/test_fewer_rows_than.sql
@@ -0,0 +1,9 @@
+with data as (
+
+    select * from {{ ref('data_test_fewer_rows_than_table_1') }}
+
+)
+
+select
+    field
+from data
\ No newline at end of file
diff --git a/macros/schema_tests/fewer_rows_than.sql b/macros/schema_tests/fewer_rows_than.sql
new file mode 100644
index 00000000..93254ca9
--- /dev/null
+++ b/macros/schema_tests/fewer_rows_than.sql
@@ -0,0 +1,35 @@
+{% macro test_fewer_rows_than(model) %}
+
+{% set compare_model = kwargs.get('compare_model', kwargs.get('arg')) %}
+
+with a as (
+
+    select count(*) as count_model from {{ model }}
+
+),
+b as (
+
+    select count(*) as count_comparison from {{ compare_model }}
+
+),
+counts as (
+
+    select
+        (select count_model from a) as count_model,
+        (select count_comparison from b) as count_comparison
+
+),
+final as (
+
+    select 
+        case
+            when count_model > count_comparison then count_model - count_comparison + 1
+            when count_model = count_comparison then count_model - count_comparison
+        else 0 end as excess_rows
+    from counts
+
+)
+
+select excess_rows from final
+
+{% endmacro %}

From 033dce9d7bb4b5dcd41c39ce4427ca7956d1346c Mon Sep 17 00:00:00 2001
From: Dan M <47741043+dmarts@users.noreply.github.com>
Date: Tue, 5 Jan 2021 16:28:15 +0000
Subject: [PATCH 2/2] Update fewer_rows_than.sql

---
 macros/schema_tests/fewer_rows_than.sql | 20 ++++++++++++--------
 1 file changed, 12 insertions(+), 8 deletions(-)

diff --git a/macros/schema_tests/fewer_rows_than.sql b/macros/schema_tests/fewer_rows_than.sql
index 93254ca9..175c855a 100644
--- a/macros/schema_tests/fewer_rows_than.sql
+++ b/macros/schema_tests/fewer_rows_than.sql
@@ -4,32 +4,36 @@
 
 with a as (
 
-    select count(*) as count_model from {{ model }}
+    select count(*) as count_ourmodel from {{ model }}
 
 ),
 b as (
 
-    select count(*) as count_comparison from {{ compare_model }}
+    select count(*) as count_comparisonmodel from {{ compare_model }}
 
 ),
 counts as (
 
     select
-        (select count_model from a) as count_model,
-        (select count_comparison from b) as count_comparison
+        (select count_ourmodel from a) as count_model_with_fewer_rows,
+        (select count_comparisonmodel from b) as count_model_with_more_rows
 
 ),
 final as (
 
     select 
         case
-            when count_model > count_comparison then count_model - count_comparison + 1
-            when count_model = count_comparison then count_model - count_comparison
-        else 0 end as excess_rows
+            -- fail the test if we have more rows than the reference model and return the row count delta
+            when count_model_with_fewer_rows > count_model_with_more_rows then (count_model_with_fewer_rows - count_model_with_more_rows)
+            -- fail the test if they are the same number
+            when count_model = count_comparison then 1
+            -- pass the test if the delta is positive (i.e. return the number 0)
+            else 0 
+    end as row_count_delta
     from counts
 
 )
 
-select excess_rows from final
+select row_count_delta from final
 
 {% endmacro %}