require "./check"

module Scope
  @[Meta(name: "Unused Indexes", desc: "Stats on barely used and unused indexes")]
  class UnusedIndexes < Check
    def query
      <<-SQL
        SELECT
          schemaname || '.' || relname AS table,
          indexrelname AS index,
          pg_size_pretty(pg_relation_size(i.indexrelid)) AS "index size",
          idx_scan as "index scans"
        FROM pg_stat_user_indexes ui
        JOIN pg_index i ON ui.indexrelid = i.indexrelid
        WHERE NOT indisunique AND idx_scan < 50 AND pg_relation_size(relid) > 5 * 8192
        ORDER BY pg_relation_size(i.indexrelid) / nullif(idx_scan, 0) DESC NULLS FIRST,
        pg_relation_size(i.indexrelid) DESC;
      SQL
    end
  end
end

# SQL modified from https://github.com/heroku/heroku-pg-extras/releases/tag/v1.2.3
#
# The MIT License (MIT)
#
# Copyright Â© Heroku 2008 - 2014
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# a copy of this software and associated documentation files (the
# "Software"), to deal in the Software without restriction, including
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# permit persons to whom the Software is furnished to do so, subject to
# the following conditions:
#
# The above copyright notice and this permission notice shall be
# included in all copies or substantial portions of the Software.
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# TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
# SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
