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# See http://doc.gitlab.com/ce/development/migration_style_guide.html
# for more information on how to write migrations for GitLab.
class AddPartialIndexForLabelsTemplate < ActiveRecord::Migration
include Gitlab::Database::MigrationHelpers
# Set this constant to true if this migration requires downtime.
DOWNTIME = false
# When a migration requires downtime you **must** uncomment the following
# constant and define a short and easy to understand explanation as to why the
# migration requires downtime.
# DOWNTIME_REASON = ''
# When using the methods "add_concurrent_index", "remove_concurrent_index" or
# "add_column_with_default" you must disable the use of transactions
# as these methods can not run in an existing transaction.
# When using "add_concurrent_index" or "remove_concurrent_index" methods make sure
# that either of them is the _only_ method called in the migration,
# any other changes should go in a separate migration.
# This ensures that upon failure _only_ the index creation or removing fails
# and can be retried or reverted easily.
#
# To disable transactions uncomment the following line and remove these
# comments:
disable_ddl_transaction!
# Note this is a partial index in Postgres but MySQL will ignore the
# partial index clause. By making it an index on "template" this
# means the index will still accomplish the same goal of optimizing
# a query with "where template = true" on MySQL -- it'll just take
# more space. In this case the number of records with template=true
# is expected to be very small (small enough to display on a single
# web page) so it's ok to filter or sort them without the index
# anyways.
def up
add_concurrent_index "labels", ["template"], where: "template"
end
def down
remove_concurrent_index "labels", ["template"], where: "template"
end
end
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