">
<% if @query_stats_enabled %>
Query stats are enabled
<% else %>
Query stats are not enabled
<% end %>
">
<% if !@query_stats_enabled %>
Query stats must be enabled for slow queries
<% elsif @slow_queries.any? %>
<%= pluralize(@slow_queries.size, "slow query") %>
<% else %>
No slow queries
<% end %>
">
<% if @long_running_queries.any? %>
<%= pluralize(@long_running_queries.size, "long running query") %>
<% else %>
No long running queries
<% end %>
">
<% if @good_cache_rate %>
Cache hit rate above 99%
<% else %>
Low cache hit rate
<% end %>
">
<% if @missing_indexes.any? %>
<%= pluralize(@missing_indexes.size, "table appears", "tables appear") %> to be missing indexes
<% else %>
No missing indexes
<% end %>
">
<% if @unused_indexes.any? %>
<%= pluralize(@unused_indexes.size, "unused index", "unused indexes") %>
<% else %>
No unused indexes
<% end %>
<% if !@query_stats_enabled %>
Query Stats
<% if @query_stats_available %>
Query stats are available but not enabled.
<%= button_to "Enable", enable_query_stats_path, class: "btn btn-info" %>
<% elsif @rds %>
Query stats are not available on Amazon RDS. <%= link_to "Tell Amazon you want this.", "https://forums.aws.amazon.com/thread.jspa?messageID=548724", target: "_blank" %>
<% else %>
Make them available by adding the following lines to postgresql.conf:
shared_preload_libraries = 'pg_stat_statements'
pg_stat_statements.track = all
Restart the server for the changes to take effect.
<% end %>
<% end %>
<% if @query_stats_enabled && @slow_queries.any? %>
Slow Queries
Slow queries take 20 ms or more on average and have been called at least 100 times.
<%= link_to "Run EXPLAIN", explain_path %> on queries to see where to add indexes.
<%= render partial: "query_stats_table", locals: {queries: @slow_queries} %>
<% end %>
<% if @long_running_queries.any? %>
Low Cache Hit Rate
Index Hit Rate: <%= (@index_hit_rate * 100).round(1) %>%
Table Hit Rate: <%= (@table_hit_rate * 100).round(1) %>%
The cache hit rate <%= link_to "should be above 99%", "https://devcenter.heroku.com/articles/understanding-postgres-data-caching", target: "_blank" %> in most cases. You can often increase this by adding more memory.
<% end %>
<% if @missing_indexes.any? %>
Missing Indexes
These tables have a large number of rows but indexes are not used often. Add indexes for faster queries.
| Table |
% of Time Index Used |
Rows in Table |
<% @missing_indexes.each do |query| %>
| <%= query["table"] %> |
<%= query["percent_of_times_index_used"] %> |
<%= number_with_delimiter(query["rows_in_table"]) %> |
<% end %>
<% end %>
<% if @unused_indexes.any? %>
Unused Indexes
Unused indexes cause unnecessary overhead. Remove them for faster writes.
| Name |
Index Size |
Index Scans |
<% @unused_indexes.each do |query| %>
| <%= query["index"] %> on <%= query["table"] %> |
<%= query["index_size"] %> |
<%= query["index_scans"] %> |
<% end %>
<% end %>