diff --git a/CHANGELOG.md b/CHANGELOG.md
index 626c9284..871a76bc 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -50,6 +50,7 @@ If you were relying on the position to match up your optional arguments, this ma
 
 ## Fixes
 * Handle booleans gracefully in the unpivot macro ([#305](https://github.com/fishtown-analytics/dbt-utils/pull/305) [@avishalom](https://github.com/avishalom))
+* Fix a bug in `get_relation_by_prefix` that happens with Snowflake external tables. Now the macro will retrieve tables that match the prefix which are external tables ([#350](https://github.com/fishtown-analytics/dbt-utils/issues/350))
 
 
 # dbt-utils v0.6.4
diff --git a/README.md b/README.md
index 16bf98a7..0886268c 100644
--- a/README.md
+++ b/README.md
@@ -1088,9 +1088,10 @@ We welcome contributions to this repo! To contribute a new feature or a fix, ple
 
 ### Dispatch macros
 
-**Note:** This is primarily relevant to users and maintainers of community-supported
-database plugins. If you use Postgres, Redshift, Snowflake, or Bigquery, this likely
-does not apply to you.
+**Note:** This is primarily relevant to:
+- Users and maintainers of community-supported [adapter plugins](https://docs.getdbt.com/docs/available-adapters)
+- Users who wish to override a low-lying `dbt_utils` macro with a custom implementation, and have that implementation used by other `dbt_utils` macros
+If you use Postgres, Redshift, Snowflake, or Bigquery, this likely does not apply to you.
 
 dbt v0.18.0 introduces `adapter.dispatch()`, a reliable way to define different implementations of the same macro
 across different databases.
@@ -1101,15 +1102,17 @@ variable in your project, when dbt searches for implementations of a dispatched
 `dbt_utils` macro, it will search through your listed packages _before_ using
 the implementations defined in `dbt_utils`.
 
-Set the variable:
+Set a variable in your `dbt_project.yml`:
 ```yml
 vars:
   dbt_utils_dispatch_list:
-    - first_package_to_search    # likely the name of your root project
+    - first_package_to_search    # likely the name of your root project (only the root folder)
     - second_package_to_search   # likely an "add-on" package, such as spark_utils
     # dbt_utils is always the last place searched
 ```
 
+If overriding a dispatched macro with a custom implementation in your own project's `macros/` directory, you must name your custom macro with a prefix: either `default__` (note the two underscores), or the name of your adapter followed by two underscores. For example, if you're running on Postgres and wish to override the behavior of `dbt_utils.datediff` (such that `dbt_utils.date_spine` will use your version instead), you can do this by defining a macro called either `default__datediff` or `postgres__datediff`.
+
 When running on Spark, if dbt needs to dispatch `dbt_utils.datediff`, it will search for the following in order:
 ```
 first_package_to_search.spark__datediff
diff --git a/macros/sql/get_tables_by_pattern_sql.sql b/macros/sql/get_tables_by_pattern_sql.sql
index 3970aa38..d06291a9 100644
--- a/macros/sql/get_tables_by_pattern_sql.sql
+++ b/macros/sql/get_tables_by_pattern_sql.sql
@@ -10,6 +10,8 @@
             table_name as "table_name",
             case table_type
                 when 'BASE TABLE' then 'table'
+                when 'EXTERNAL TABLE' then 'external'
+                when 'MATERIALIZED VIEW' then 'materializedview'
                 else lower(table_type)
             end as "table_type"
         from {{ database }}.information_schema.tables