Add if_not_exists to create_view and if_exists to drop_view

.gitignore

@@ -18,3 +18,4 @@ tmp
 gemfiles/*.lock
 .DS_Store
 .ruby-version
+.ruby-gemset

lib/scenic/adapters/postgres.rb

@@ -55,9 +55,14 @@ def views
       #
       # @param name The name of the view to create
       # @param sql_definition The SQL schema for the view.
+      # @param if_not_exists [Boolean] Default: false. Set to true to create
+      #   view only if it does not exist.
       #
       # @return [void]
-      def create_view(name, sql_definition)
+      def create_view(name, sql_definition, if_not_exists: false)
+        if if_not_exists
+          return if views.any? { |view| view.name == name }
+        end
         execute "CREATE VIEW #{quote_table_name(name)} AS #{sql_definition};"
       end
 
@@ -112,10 +117,13 @@ def replace_view(name, sql_definition)
       # This is typically called in a migration via {Statements#drop_view}.
       #
       # @param name The name of the view to drop
+      # @param if_exists [Boolean] Default: false. Set to true to drop
+      #   view only if it exists.
       #
       # @return [void]
-      def drop_view(name)
-        execute "DROP VIEW #{quote_table_name(name)};"
+      def drop_view(name, if_exists: false)
+        definition_if_exists = if_exists ? "IF EXISTS " : ""
+        execute "DROP VIEW #{definition_if_exists}#{quote_table_name(name)};"
       end
 
       # Creates a materialized view in the database
@@ -125,18 +133,21 @@ def drop_view(name)
       # @param no_data [Boolean] Default: false. Set to true to create
       #   materialized view without running the associated query. You will need
       #   to perform a non-concurrent refresh to populate with data.
+      # @param if_not_exists [Boolean] Default: false. Set to true to create
+      #   materialized view only if it does not exist.
       #
       # This is typically called in a migration via {Statements#create_view}.
       #
       # @raise [MaterializedViewsNotSupportedError] if the version of Postgres
       #   in use does not support materialized views.
       #
       # @return [void]
-      def create_materialized_view(name, sql_definition, no_data: false)
+      def create_materialized_view(name, sql_definition, no_data: false, if_not_exists: false)
         raise_unless_materialized_views_supported
 
+        definition_if_not_exists = if_not_exists ? "IF NOT EXISTS " : ""
         execute <<-SQL
-  CREATE MATERIALIZED VIEW #{quote_table_name(name)} AS
+  CREATE MATERIALIZED VIEW #{definition_if_not_exists}#{quote_table_name(name)} AS
   #{sql_definition.rstrip.chomp(';')}
   #{'WITH NO DATA' if no_data};
         SQL
@@ -174,13 +185,16 @@ def update_materialized_view(name, sql_definition, no_data: false)
       # This is typically called in a migration via {Statements#update_view}.
       #
       # @param name The name of the materialized view to drop.
+      # @param if_exists [Boolean] Default: false. Set to true to drop
+      #   materialized view only if it exists.
       # @raise [MaterializedViewsNotSupportedError] if the version of Postgres
       #   in use does not support materialized views.
       #
       # @return [void]
-      def drop_materialized_view(name)
+      def drop_materialized_view(name, if_exists: false)
         raise_unless_materialized_views_supported
-        execute "DROP MATERIALIZED VIEW #{quote_table_name(name)};"
+        definition_if_exists = if_exists ? "IF EXISTS " : ""
+        execute "DROP MATERIALIZED VIEW #{definition_if_exists}#{quote_table_name(name)};"
       end
 
       # Refreshes a materialized view from its SQL schema.

lib/scenic/statements.rb

@@ -12,6 +12,8 @@ module Statements
     # @param materialized [Boolean, Hash] Set to true to create a materialized
     #   view. Set to { no_data: true } to create materialized view without
     #   loading data. Defaults to false.
+    # @param if_not_exists [Boolean] Set to true to only create the view if it
+    #   does not already exist. Defaults to false.
     # @return The database response from executing the create statement.
     #
     # @example Create from `db/views/searches_v02.sql`
@@ -22,7 +24,7 @@ module Statements
     #     SELECT * FROM users WHERE users.active = 't'
     #   SQL
     #
-    def create_view(name, version: nil, sql_definition: nil, materialized: false)
+    def create_view(name, version: nil, sql_definition: nil, materialized: false, if_not_exists: false)
       if version.present? && sql_definition.present?
         raise(
           ArgumentError,
@@ -41,9 +43,10 @@ def create_view(name, version: nil, sql_definition: nil, materialized: false)
           name,
           sql_definition,
           no_data: no_data(materialized),
+          if_not_exists: if_not_exists,
         )
       else
-        Scenic.database.create_view(name, sql_definition)
+        Scenic.database.create_view(name, sql_definition, if_not_exists: if_not_exists)
       end
     end
 
@@ -55,16 +58,18 @@ def create_view(name, version: nil, sql_definition: nil, materialized: false)
     #   `version` argument to {#create_view}.
     # @param materialized [Boolean] Set to true if dropping a meterialized view.
     #   defaults to false.
+    # @param if_exists [Boolean] Set to true to only drop the view if itexists.
+    #   Defaults to false.
     # @return The database response from executing the drop statement.
     #
     # @example Drop a view, rolling back to version 3 on rollback
     #   drop_view(:users_who_recently_logged_in, revert_to_version: 3)
     #
-    def drop_view(name, revert_to_version: nil, materialized: false)
+    def drop_view(name, revert_to_version: nil, materialized: false, if_exists: false)
       if materialized
-        Scenic.database.drop_materialized_view(name)
+        Scenic.database.drop_materialized_view(name, if_exists: if_exists)
       else
-        Scenic.database.drop_view(name)
+        Scenic.database.drop_view(name, if_exists: if_exists)
       end
     end
 

spec/scenic/adapters/postgres_spec.rb

@@ -11,6 +11,22 @@ module Adapters
 
           expect(adapter.views.map(&:name)).to include("greetings")
         end
+
+        it "successfully creates a view with :if_not_exists if view does not exist" do
+          adapter = Postgres.new
+
+          adapter.create_view("greetings", "SELECT text 'hi' AS greeting", if_not_exists: true)
+
+          expect(adapter.views.map(&:name)).to include("greetings")
+        end
+
+        it "does not raise an error with :if_not_exists if view exists" do
+          adapter = Postgres.new
+
+          adapter.create_view("greetings", "SELECT text 'hi' AS greeting")
+          expect { adapter.create_view("greetings", "SELECT text 'hi' AS greeting", if_not_exists: true) }
+            .not_to raise_error
+        end
       end
 
       describe "#create_materialized_view" do
@@ -77,6 +93,21 @@ module Adapters
 
           expect(adapter.views.map(&:name)).not_to include("greetings")
         end
+
+        it "successfully drops with :if_exists if view exists" do
+          adapter = Postgres.new
+
+          adapter.create_view("greetings", "SELECT text 'hi' AS greeting")
+          adapter.drop_view("greetings", if_exists: true)
+
+          expect(adapter.views.map(&:name)).not_to include("greetings")
+        end
+
+        it "does not raise error with :if_exists if view does not exist" do
+          adapter = Postgres.new
+
+          expect { adapter.drop_view("greetings", if_exists: true) }.not_to raise_error
+        end
       end
 
       describe "#drop_materialized_view" do
@@ -92,6 +123,24 @@ module Adapters
           expect(adapter.views.map(&:name)).not_to include("greetings")
         end
 
+        it "successfully drops with :if_exists if view exists" do
+          adapter = Postgres.new
+
+          adapter.create_materialized_view(
+            "greetings",
+            "SELECT text 'hi' AS greeting",
+          )
+          adapter.drop_materialized_view("greetings", if_exists: true)
+
+          expect(adapter.views.map(&:name)).not_to include("greetings")
+        end
+
+        it "does not raise error with :if_exists if view does not exist" do
+          adapter = Postgres.new
+
+          expect { adapter.drop_materialized_view("greetings", if_exists: true) }.not_to raise_error
+        end
+
         it "raises an exception if the version of PostgreSQL is too old" do
           connection = double("Connection", supports_materialized_views?: false)
           connectable = double("Connectable", connection: connection)

spec/scenic/statements_spec.rb

@@ -18,7 +18,7 @@ module Scenic
         connection.create_view :views, version: version
 
         expect(Scenic.database).to have_received(:create_view)
-          .with(:views, definition_stub.to_sql)
+          .with(:views, definition_stub.to_sql, if_not_exists: false)
       end
 
       it "creates a view from a text definition" do
@@ -27,7 +27,7 @@ module Scenic
         connection.create_view(:views, sql_definition: sql_definition)
 
         expect(Scenic.database).to have_received(:create_view)
-          .with(:views, sql_definition)
+          .with(:views, sql_definition, if_not_exists: false)
       end
 
       it "creates version 1 of the view if neither version nor sql_defintion are provided" do
@@ -40,7 +40,7 @@ module Scenic
         connection.create_view :views
 
         expect(Scenic.database).to have_received(:create_view)
-          .with(:views, definition_stub.to_sql)
+          .with(:views, definition_stub.to_sql, if_not_exists: false)
       end
 
       it "raises an error if both version and sql_defintion are provided" do
@@ -58,7 +58,7 @@ module Scenic
         connection.create_view(:views, version: 1, materialized: true)
 
         expect(Scenic.database).to have_received(:create_materialized_view)
-          .with(:views, definition.to_sql, no_data: false)
+          .with(:views, definition.to_sql, no_data: false, if_not_exists: false)
       end
     end
 
@@ -74,15 +74,34 @@ module Scenic
         )
 
         expect(Scenic.database).to have_received(:create_materialized_view)
-          .with(:views, definition.to_sql, no_data: true)
+          .with(:views, definition.to_sql, no_data: true, if_not_exists: false)
+      end
+    end
+
+    describe "create_view :materialized with :if_not_exists" do
+      it "sends the create_materialized_view message with if not exists" do
+        definition = instance_double("Scenic::Definition", to_sql: "definition")
+        allow(Definition).to receive(:new).and_return(definition)
+
+        connection.create_view(:views, version: 1, materialized: true, if_not_exists: true)
+
+        expect(Scenic.database).to have_received(:create_materialized_view)
+          .with(:views, definition.to_sql, no_data: false, if_not_exists: true)
       end
     end
 
     describe "drop_view" do
       it "removes a view from the database" do
         connection.drop_view :name
 
-        expect(Scenic.database).to have_received(:drop_view).with(:name)
+        expect(Scenic.database).to have_received(:drop_view).with(:name, if_exists: false)
+      end
+
+      it "removes a view from the database if it exists" do
+        connection.drop_view :name, if_exists: true
+
+        expect(Scenic.database).to have_received(:drop_view)
+          .with(:name, if_exists: true)
       end
     end
 
@@ -92,6 +111,13 @@ module Scenic
 
         expect(Scenic.database).to have_received(:drop_materialized_view)
       end
+
+      it "removes a materialized view from the database if it exists" do
+        connection.drop_view :name, materialized: true, if_exists: true
+
+        expect(Scenic.database).to have_received(:drop_materialized_view)
+          .with(:name, if_exists: true)
+      end
     end
 
     describe "update_view" do