Added cop to blacklist the use of hash indexesrubocop-hash-index

These indexes are not recorded in the WAL (at least until PostgreSQL
10) and this isn't worth the minor performance improvement over btree
indexes.

1 files changed, 53 insertions, 0 deletions

diff --git a/spec/rubocop/cop/migration/hash_index_spec.rb b/spec/rubocop/cop/migration/hash_index_spec.rb
new file mode 100644
index 00000000000..9a8576a19e5
--- /dev/null
+++ b/spec/rubocop/cop/migration/hash_index_spec.rb
@@ -0,0 +1,53 @@
+require 'spec_helper'
+
+require 'rubocop'
+require 'rubocop/rspec/support'
+
+require_relative '../../../../rubocop/cop/migration/hash_index'
+
+describe RuboCop::Cop::Migration::HashIndex do
+  include CopHelper
+
+  subject(:cop) { described_class.new }
+
+  context 'in migration' do
+    before do
+      allow(cop).to receive(:in_migration?).and_return(true)
+    end
+
+    it 'registers an offense when creating a hash index' do
+      inspect_source(cop, 'def change; add_index :table, :column, using: :hash; end')
+
+      aggregate_failures do
+        expect(cop.offenses.size).to eq(1)
+        expect(cop.offenses.map(&:line)).to eq([1])
+      end
+    end
+
+    it 'registers an offense when creating a concurrent hash index' do
+      inspect_source(cop, 'def change; add_concurrent_index :table, :column, using: :hash; end')
+
+      aggregate_failures do
+        expect(cop.offenses.size).to eq(1)
+        expect(cop.offenses.map(&:line)).to eq([1])
+      end
+    end
+
+    it 'registers an offense when creating a hash index using t.index' do
+      inspect_source(cop, 'def change; t.index :table, :column, using: :hash; end')
+
+      aggregate_failures do
+        expect(cop.offenses.size).to eq(1)
+        expect(cop.offenses.map(&:line)).to eq([1])
+      end
+    end
+  end
+
+  context 'outside of migration' do
+    it 'registers no offense' do
+      inspect_source(cop, 'def change; index :table, :column, using: :hash; end')
+
+      expect(cop.offenses.size).to eq(0)
+    end
+  end
+end