Merge branch 'ab-43887-concurrent-migration-helpers' into 'master'

Convenient use of concurrent migration helpers

Closes #43887

See merge request gitlab-org/gitlab-ce!17888

db/migrate/20170530130129_project_foreign_keys_with_cascading_deletes.rb

@@ -154,7 +154,7 @@ class ProjectForeignKeysWithCascadingDeletes < ActiveRecord::Migration
   end
   def add_foreign_key_if_not_exists(source, target, column:)
-    return if foreign_key_exists?(source, column)
+    return if foreign_key_exists?(source, target, column: column)
     add_concurrent_foreign_key(source, target, column: column)
   end
@@ -175,12 +175,6 @@ class ProjectForeignKeysWithCascadingDeletes < ActiveRecord::Migration
   rescue ArgumentError
   end
-  def foreign_key_exists?(table, column)
-    foreign_keys(table).any? do |key|
-      key.options[:column] == column.to_s
-    end
-  end
-
   def connection
     # Rails memoizes connection objects, but this causes them to be shared
     # amongst threads; we don't want that.

db/migrate/20170703102400_add_stage_id_foreign_key_to_builds.rb

@@ -10,13 +10,13 @@ class AddStageIdForeignKeyToBuilds < ActiveRecord::Migration
       add_concurrent_index(:ci_builds, :stage_id)
     end
-    unless foreign_key_exists?(:ci_builds, :stage_id)
+    unless foreign_key_exists?(:ci_builds, :ci_stages, column: :stage_id)
       add_concurrent_foreign_key(:ci_builds, :ci_stages, column: :stage_id, on_delete: :cascade)
     end
   end
   def down
-    if foreign_key_exists?(:ci_builds, :stage_id)
+    if foreign_key_exists?(:ci_builds, column: :stage_id)
       remove_foreign_key(:ci_builds, column: :stage_id)
     end
@@ -24,12 +24,4 @@ class AddStageIdForeignKeyToBuilds < ActiveRecord::Migration
       remove_concurrent_index(:ci_builds, :stage_id)
     end
   end
-
-  private
-
-  def foreign_key_exists?(table, column)
-    foreign_keys(:ci_builds).any? do |key|
-      key.options[:column] == column.to_s
-    end
-  end
 end

db/migrate/20170713104829_add_foreign_key_to_merge_requests.rb

@@ -23,23 +23,15 @@ class AddForeignKeyToMergeRequests < ActiveRecord::Migration
       merge_requests.update_all(head_pipeline_id: nil)
     end
-    unless foreign_key_exists?(:merge_requests, :head_pipeline_id)
+    unless foreign_key_exists?(:merge_requests, column: :head_pipeline_id)
       add_concurrent_foreign_key(:merge_requests, :ci_pipelines,
                                  column: :head_pipeline_id, on_delete: :nullify)
     end
   end
   def down
-    if foreign_key_exists?(:merge_requests, :head_pipeline_id)
+    if foreign_key_exists?(:merge_requests, column: :head_pipeline_id)
       remove_foreign_key(:merge_requests, column: :head_pipeline_id)
     end
   end
-
-  private
-
-  def foreign_key_exists?(table, column)
-    foreign_keys(table).any? do |key|
-      key.options[:column] == column.to_s
-    end
-  end
 end

db/post_migrate/20180223124427_build_user_interacted_projects_table.rb

@@ -26,11 +26,11 @@ class BuildUserInteractedProjectsTable < ActiveRecord::Migration
   def down
     execute "TRUNCATE user_interacted_projects"
-    if foreign_key_exists?(:user_interacted_projects, :user_id)
+    if foreign_key_exists?(:user_interacted_projects, :users)
       remove_foreign_key :user_interacted_projects, :users
     end
-    if foreign_key_exists?(:user_interacted_projects, :project_id)
+    if foreign_key_exists?(:user_interacted_projects, :projects)
       remove_foreign_key :user_interacted_projects, :projects
     end
@@ -115,7 +115,7 @@ class BuildUserInteractedProjectsTable < ActiveRecord::Migration
     end
     def create_fk(table, target, column)
-      return if foreign_key_exists?(table, column)
+      return if foreign_key_exists?(table, target, column: column)
       add_foreign_key table, target, column: column, on_delete: :cascade
     end
@@ -158,11 +158,11 @@ class BuildUserInteractedProjectsTable < ActiveRecord::Migration
         add_concurrent_index :user_interacted_projects, [:project_id, :user_id], unique: true, name: UNIQUE_INDEX_NAME
       end
-      unless foreign_key_exists?(:user_interacted_projects, :user_id)
+      unless foreign_key_exists?(:user_interacted_projects, :users, column: :user_id)
         add_concurrent_foreign_key :user_interacted_projects, :users, column: :user_id, on_delete: :cascade
       end
-      unless foreign_key_exists?(:user_interacted_projects, :project_id)
+      unless foreign_key_exists?(:user_interacted_projects, :projects, column: :project_id)
         add_concurrent_foreign_key :user_interacted_projects, :projects, column: :project_id, on_delete: :cascade
       end
     end

doc/development/migration_style_guide.md

@@ -136,11 +136,14 @@ class MyMigration < ActiveRecord::Migration
   disable_ddl_transaction!
   def up
-    remove_concurrent_index :table_name, :column_name if index_exists?(:table_name, :column_name)
+    remove_concurrent_index :table_name, :column_name
   end
 end
 ```
+Note that it is not necessary to check if the index exists prior to
+removing it.
+
 ## Adding indexes
 If you need to add a unique index please keep in mind there is the possibility

lib/gitlab/database/migration_helpers.rb

@@ -59,6 +59,11 @@ module Gitlab
           disable_statement_timeout
         end
+        if index_exists?(table_name, column_name, options)
+          Rails.logger.warn "Index not created because it already exists (this may be due to an aborted migration or similar): table_name: #{table_name}, column_name: #{column_name}"
+          return
+        end
+
         add_index(table_name, column_name, options)
       end
@@ -83,6 +88,11 @@ module Gitlab
           disable_statement_timeout
         end
+        unless index_exists?(table_name, column_name, options)
+          Rails.logger.warn "Index not removed because it does not exist (this may be due to an aborted migration or similar): table_name: #{table_name}, column_name: #{column_name}"
+          return
+        end
+
         remove_index(table_name, options.merge({ column: column_name }))
       end
@@ -107,6 +117,11 @@ module Gitlab
           disable_statement_timeout
         end
+        unless index_exists_by_name?(table_name, index_name)
+          Rails.logger.warn "Index not removed because it does not exist (this may be due to an aborted migration or similar): table_name: #{table_name}, index_name: #{index_name}"
+          return
+        end
+
         remove_index(table_name, options.merge({ name: index_name }))
       end
@@ -140,6 +155,13 @@ module Gitlab
         # of PostgreSQL's "VALIDATE CONSTRAINT". As a result we'll just fall
         # back to the normal foreign key procedure.
         if Database.mysql?
+          if foreign_key_exists?(source, target, column: column)
+            Rails.logger.warn "Foreign key not created because it exists already " \
+              "(this may be due to an aborted migration or similar): " \
+              "source: #{source}, target: #{target}, column: #{column}"
+            return
+          end
+
           return add_foreign_key(source, target,
                                  column: column,
                                  on_delete: on_delete)
@@ -151,25 +173,43 @@ module Gitlab
         key_name = concurrent_foreign_key_name(source, column)
-        # Using NOT VALID allows us to create a key without immediately
-        # validating it. This means we keep the ALTER TABLE lock only for a
-        # short period of time. The key _is_ enforced for any newly created
-        # data.
-        execute <<-EOF.strip_heredoc
-        ALTER TABLE #{source}
-        ADD CONSTRAINT #{key_name}
-        FOREIGN KEY (#{column})
-        REFERENCES #{target} (id)
-        #{on_delete ? "ON DELETE #{on_delete.upcase}" : ''}
-        NOT VALID;
-        EOF
+        unless foreign_key_exists?(source, target, column: column)
+          Rails.logger.warn "Foreign key not created because it exists already " \
+            "(this may be due to an aborted migration or similar): " \
+            "source: #{source}, target: #{target}, column: #{column}"
+
+          # Using NOT VALID allows us to create a key without immediately
+          # validating it. This means we keep the ALTER TABLE lock only for a
+          # short period of time. The key _is_ enforced for any newly created
+          # data.
+          execute <<-EOF.strip_heredoc
+          ALTER TABLE #{source}
+          ADD CONSTRAINT #{key_name}
+          FOREIGN KEY (#{column})
+          REFERENCES #{target} (id)
+          #{on_delete ? "ON DELETE #{on_delete.upcase}" : ''}
+          NOT VALID;
+          EOF
+        end
         # Validate the existing constraint. This can potentially take a very
         # long time to complete, but fortunately does not lock the source table
         # while running.
+        #
+        # Note this is a no-op in case the constraint is VALID already
         execute("ALTER TABLE #{source} VALIDATE CONSTRAINT #{key_name};")
       end
+      def foreign_key_exists?(source, target = nil, column: nil)
+        foreign_keys(source).any? do |key|
+          if column
+            key.options[:column].to_s == column.to_s
+          else
+            key.to_table.to_s == target.to_s
+          end
+        end
+      end
+
       # Returns the name for a concurrent foreign key.
       #
       # PostgreSQL constraint names have a limit of 63 bytes. The logic used
@@ -860,12 +900,6 @@ into similar problems in the future (e.g. when new tables are created).
         end
       end
-      def foreign_key_exists?(table, column)
-        foreign_keys(table).any? do |key|
-          key.options[:column] == column.to_s
-        end
-      end
-
       # Rails' index_exists? doesn't work when you only give it a table and index
       # name. As such we have to use some extra code to check if an index exists for
       # a given name.

spec/lib/gitlab/database/migration_helpers_spec.rb

@@ -67,17 +67,35 @@ describe Gitlab::Database::MigrationHelpers do
           model.add_concurrent_index(:users, :foo, unique: true)
         end
+
+        it 'does nothing if the index exists already' do
+          expect(model).to receive(:index_exists?)
+            .with(:users, :foo, { algorithm: :concurrently, unique: true }).and_return(true)
+          expect(model).not_to receive(:add_index)
+
+          model.add_concurrent_index(:users, :foo, unique: true)
+        end
       end
       context 'using MySQL' do
-        it 'creates a regular index' do
-          expect(Gitlab::Database).to receive(:postgresql?).and_return(false)
+        before do
+          allow(Gitlab::Database).to receive(:postgresql?).and_return(false)
+        end
+        it 'creates a regular index' do
           expect(model).to receive(:add_index)
             .with(:users, :foo, {})
           model.add_concurrent_index(:users, :foo)
         end
+
+        it 'does nothing if the index exists already' do
+          expect(model).to receive(:index_exists?)
+            .with(:users, :foo, { unique: true }).and_return(true)
+          expect(model).not_to receive(:add_index)
+
+          model.add_concurrent_index(:users, :foo, unique: true)
+        end
       end
     end
@@ -95,6 +113,7 @@ describe Gitlab::Database::MigrationHelpers do
     context 'outside a transaction' do
       before do
         allow(model).to receive(:transaction_open?).and_return(false)
+        allow(model).to receive(:index_exists?).and_return(true)
       end
       context 'using PostgreSQL' do
@@ -103,18 +122,41 @@ describe Gitlab::Database::MigrationHelpers do
           allow(model).to receive(:disable_statement_timeout)
         end
-        it 'removes the index concurrently by column name' do
-          expect(model).to receive(:remove_index)
-            .with(:users, { algorithm: :concurrently, column: :foo })
-          model.remove_concurrent_index(:users, :foo)
+        describe 'by column name' do
+          it 'removes the index concurrently' do
+            expect(model).to receive(:remove_index)
+              .with(:users, { algorithm: :concurrently, column: :foo })
+            model.remove_concurrent_index(:users, :foo)
+          end
+
+          it 'does nothing if the index does not exist' do
+            expect(model).to receive(:index_exists?)
+              .with(:users, :foo, { algorithm: :concurrently, unique: true }).and_return(false)
+            expect(model).not_to receive(:remove_index)
+
+            model.remove_concurrent_index(:users, :foo, unique: true)
+          end
         end
-        it 'removes the index concurrently by index name' do
-          expect(model).to receive(:remove_index)
-            .with(:users, { algorithm: :concurrently, name: "index_x_by_y" })
-          model.remove_concurrent_index_by_name(:users, "index_x_by_y")
+        describe 'by index name' do
+          before do
+            allow(model).to receive(:index_exists_by_name?).with(:users, "index_x_by_y").and_return(true)
+          end
+
+          it 'removes the index concurrently by index name' do
+            expect(model).to receive(:remove_index)
+              .with(:users, { algorithm: :concurrently, name: "index_x_by_y" })
+
+            model.remove_concurrent_index_by_name(:users, "index_x_by_y")
+          end
+
+          it 'does nothing if the index does not exist' do
+            expect(model).to receive(:index_exists_by_name?).with(:users, "index_x_by_y").and_return(false)
+            expect(model).not_to receive(:remove_index)
+            model.remove_concurrent_index_by_name(:users, "index_x_by_y")
+          end
         end
       end
@@ -141,6 +183,10 @@ describe Gitlab::Database::MigrationHelpers do
   end
   describe '#add_concurrent_foreign_key' do
+    before do
+      allow(model).to receive(:foreign_key_exists?).and_return(false)
+    end
+
     context 'inside a transaction' do
       it 'raises an error' do
         expect(model).to receive(:transaction_open?).and_return(true)
@@ -157,14 +203,23 @@ describe Gitlab::Database::MigrationHelpers do
       end
       context 'using MySQL' do
-        it 'creates a regular foreign key' do
+        before do
           allow(Gitlab::Database).to receive(:mysql?).and_return(true)
+        end
+        it 'creates a regular foreign key' do
           expect(model).to receive(:add_foreign_key)
             .with(:projects, :users, column: :user_id, on_delete: :cascade)
           model.add_concurrent_foreign_key(:projects, :users, column: :user_id)
         end
+
+        it 'does not create a foreign key if it exists already' do
+          expect(model).to receive(:foreign_key_exists?).with(:projects, :users, column: :user_id).and_return(true)
+          expect(model).not_to receive(:add_foreign_key)
+
+          model.add_concurrent_foreign_key(:projects, :users, column: :user_id)
+        end
       end
       context 'using PostgreSQL' do
@@ -189,6 +244,14 @@ describe Gitlab::Database::MigrationHelpers do
                                            column: :user_id,
                                            on_delete: :nullify)
         end
+
+        it 'does not create a foreign key if it exists already' do
+          expect(model).to receive(:foreign_key_exists?).with(:projects, :users, column: :user_id).and_return(true)
+          expect(model).not_to receive(:execute).with(/ADD CONSTRAINT/)
+          expect(model).to receive(:execute).with(/VALIDATE CONSTRAINT/)
+
+          model.add_concurrent_foreign_key(:projects, :users, column: :user_id)
+        end
       end
     end
   end
@@ -203,6 +266,29 @@ describe Gitlab::Database::MigrationHelpers do
     end
   end
+  describe '#foreign_key_exists?' do
+    before do
+      key = ActiveRecord::ConnectionAdapters::ForeignKeyDefinition.new(:projects, :users, { column: :non_standard_id })
+      allow(model).to receive(:foreign_keys).with(:projects).and_return([key])
+    end
+
+    it 'finds existing foreign keys by column' do
+      expect(model.foreign_key_exists?(:projects, :users, column: :non_standard_id)).to be_truthy
+    end
+
+    it 'finds existing foreign keys by target table only' do
+      expect(model.foreign_key_exists?(:projects, :users)).to be_truthy
+    end
+
+    it 'compares by column name if given' do
+      expect(model.foreign_key_exists?(:projects, :users, column: :user_id)).to be_falsey
+    end
+
+    it 'compares by target if no column given' do
+      expect(model.foreign_key_exists?(:projects, :other_table)).to be_falsey
+    end
+  end
+
   describe '#disable_statement_timeout' do
     context 'using PostgreSQL' do
       it 'disables statement timeouts' do