Fix migrations for older PostgreSQL versions

- Do not care about error when creating index on PostgreSQL
- Test against PostgreSQL 9.2

1 files changed, 68 insertions, 0 deletions

diff --git a/db/post_migrate/20170503004427_update_retried_for_ci_build.rb b/db/post_migrate/20170503004427_update_retried_for_ci_build.rb
new file mode 100644
index 00000000000..705e11ed47d
--- /dev/null
+++ b/db/post_migrate/20170503004427_update_retried_for_ci_build.rb
@@ -0,0 +1,68 @@
+class UpdateRetriedForCiBuild < ActiveRecord::Migration
+  include Gitlab::Database::MigrationHelpers
+
+  DOWNTIME = false
+
+  disable_ddl_transaction!
+
+  def up
+    disable_statement_timeout
+
+    if Gitlab::Database.mysql?
+      up_mysql
+    else
+      up_postgres
+    end
+  end
+
+  def down
+  end
+
+  private
+
+  def up_mysql
+    # This is a trick to overcome MySQL limitation: 
+    # Mysql2::Error: Table 'ci_builds' is specified twice, both as a target for 'UPDATE' and as a separate source for data
+    # However, this leads to create a temporary table from `max(ci_builds.id)` which is slow and do full database update
+    execute <<-SQL.strip_heredoc
+      UPDATE ci_builds SET retried=
+        (id NOT IN (
+          SELECT * FROM (SELECT MAX(ci_builds.id) FROM ci_builds GROUP BY commit_id, name) AS latest_jobs
+        ))
+      WHERE retried IS NULL
+    SQL
+  end
+
+  def up_postgres
+    with_temporary_partial_index do
+      latest_id = <<-SQL.strip_heredoc
+        SELECT MAX(ci_builds2.id)
+          FROM ci_builds ci_builds2
+          WHERE ci_builds.commit_id=ci_builds2.commit_id
+            AND ci_builds.name=ci_builds2.name
+      SQL
+
+      # This is slow update as it does single-row query
+      # This is designed to be run as idle, or a post deployment migration
+      is_retried = Arel.sql("((#{latest_id}) != ci_builds.id)")
+
+      update_column_in_batches(:ci_builds, :retried, is_retried) do |table, query|
+        query.where(table[:retried].eq(nil))
+      end
+    end
+  end
+
+  def with_temporary_partial_index
+    if Gitlab::Database.postgresql?
+      unless index_exists?(:ci_builds, name: :index_for_ci_builds_retried_migration)
+        execute 'CREATE INDEX CONCURRENTLY index_for_ci_builds_retried_migration ON ci_builds (id) WHERE retried IS NULL;'
+      end
+    end
+
+    yield
+
+    if Gitlab::Database.postgresql? && index_exists?(:ci_builds, name: :index_for_ci_builds_retried_migration)
+      execute 'DROP INDEX CONCURRENTLY index_for_ci_builds_retried_migration'
+    end
+  end
+end