Limit CI builds queries to 7 days

This applies to EE queries only. It improves performance of those
queries significantly.

Related to https://gitlab.com/gitlab-org/gitlab-exporter/issues/58

Gemfile.lock

 PATH
   remote: .
   specs:
-    gitlab-exporter (4.2.0)
+    gitlab-exporter (5.0.1)
       connection_pool (~> 2.2.1)
       pg (~> 1.1)
       quantile (~> 0.2.0)
@@ -23,7 +23,7 @@ GEM
     powerpack (0.1.1)
     quantile (0.2.1)
     rack (2.0.7)
-    rack-protection (2.0.5)
+    rack-protection (2.0.7)
       rack
     rainbow (2.1.0)
     redis (4.1.2)
@@ -54,10 +54,10 @@ GEM
       rack (>= 1.5.0)
       rack-protection (>= 1.5.0)
       redis (>= 3.3.5, < 5)
-    sinatra (2.0.5)
+    sinatra (2.0.7)
       mustermann (~> 1.0)
       rack (~> 2.0)
-      rack-protection (= 2.0.5)
+      rack-protection (= 2.0.7)
       tilt (~> 2.0)
     tilt (2.0.9)
     unicode-display_width (1.1.0)

lib/gitlab_exporter/database/ci_builds.rb

@@ -25,6 +25,8 @@ module GitLab
               ON application_settings.id = 1
             WHERE ci_builds.type = 'Ci::Build'
               AND ci_builds.status = '%s'
+              -- The created_at filter has been introduced for performance reasons only
+              AND ci_builds.created_at > NOW() - INTERVAL '7 days'
               AND projects.pending_delete = 'f'
             GROUP BY
               projects.namespace_id,
@@ -95,6 +97,8 @@ module GitLab
               ON application_settings.id = 1
             WHERE ci_builds.type = 'Ci::Build'
               AND ci_builds.status = 'running'
+              -- The created_at filter has been introduced for performance reasons only
+              AND ci_builds.created_at > NOW() - INTERVAL '7 days'
               AND projects.pending_delete = 'f'
             GROUP BY
               ci_builds.runner_id,
@@ -171,6 +175,8 @@ module GitLab
                 ON application_settings.id = 1
               WHERE ci_builds.type = 'Ci::Build'
                 AND ci_builds.status IN ('running', 'pending')
+                -- The created_at filter has been introduced for performance reasons only
+                AND ci_builds.created_at > NOW() - INTERVAL '7 days'
               GROUP BY
                 projects.namespace_id,
                 projects.shared_runners_enabled,

lib/gitlab_exporter/version.rb

 module GitLab
   module Exporter
-    VERSION = "5.0.0".freeze
+    VERSION = "5.0.1".freeze
   end
 end