Normalize the SQL queries before sending them to Sentry

To prevent sending some sensitive information, we need to normalize the
SQL queries before we send them to Sentry. To do so, we decided to use
the gem called `pg_query` which compiles some parts of the PostgreSQL
database to make it possible to parse SQL queries.

Gemfile

@@ -307,6 +307,9 @@ gem 'rack-attack', '~> 6.3.0'
 # Sentry integration
 gem 'sentry-raven', '~> 3.0'
 
+# PostgreSQL query parsing
+gem 'gitlab-pg_query', '~> 1.3', require: 'pg_query'
+
 gem 'premailer-rails', '~> 1.10.3'
 
 # LabKit: Tracing and Correlation

Gemfile.lock

@@ -439,6 +439,7 @@ GEM
     gitlab-mail_room (0.0.7)
     gitlab-markup (1.7.1)
     gitlab-net-dns (0.9.1)
+    gitlab-pg_query (1.3.0)
     gitlab-puma (4.3.5.gitlab.3)
       nio4r (~> 2.0)
     gitlab-puma_worker_killer (0.1.1.gitlab.1)
@@ -1336,6 +1337,7 @@ DEPENDENCIES
   gitlab-mail_room (~> 0.0.7)
   gitlab-markup (~> 1.7.1)
   gitlab-net-dns (~> 0.9.1)
+  gitlab-pg_query (~> 1.3)
   gitlab-puma (~> 4.3.3.gitlab.2)
   gitlab-puma_worker_killer (~> 0.1.1.gitlab.1)
   gitlab-sidekiq-fetcher (= 0.5.2)

lib/gitlab/error_tracking.rb

@@ -153,7 +153,7 @@ module Gitlab
       def inject_sql_query_into_extra(exception, extra)
         return unless exception.is_a?(ActiveRecord::StatementInvalid)
 
-        extra[:sql] = exception.sql
+        extra[:sql] = PgQuery.normalize(exception.sql.to_s)
       end
 
       def sentry_dsn

spec/lib/gitlab/error_tracking_spec.rb

@@ -284,13 +284,13 @@ RSpec.describe Gitlab::ErrorTracking do
     end
 
     context 'when the error is kind of an `ActiveRecord::StatementInvalid`' do
-      let(:exception) { ActiveRecord::StatementInvalid.new(sql: :foo) }
+      let(:exception) { ActiveRecord::StatementInvalid.new(sql: 'SELECT "users".* FROM "users" WHERE "users"."id" = 1 AND "users"."foo" = $1') }
 
-      it 'injects the sql query into extra' do
+      it 'injects the normalized sql query into extra' do
         track_exception
 
         expect(Raven).to have_received(:capture_exception)
-          .with(exception, a_hash_including(extra: a_hash_including(sql: :foo)))
+          .with(exception, a_hash_including(extra: a_hash_including(sql: 'SELECT "users".* FROM "users" WHERE "users"."id" = $2 AND "users"."foo" = $1')))
       end
     end
   end