9b2886979a
* Do not load messages in memory, just to count them * Add Model.estimated_count * Use Model.estimated_count in task record_db_table_counts * Use size and estimated_count * Use table_name so that .estimated_count works with all models * Add comment to explain the .load.size + .each pattern
27 lines
946 B
Ruby
27 lines
946 B
Ruby
class ApplicationRecord < ActiveRecord::Base
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self.abstract_class = true
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QUERY_ESTIMATED_COUNT = <<~SQL.squish.freeze
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SELECT (
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(reltuples / GREATEST(relpages, 1)) *
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(pg_relation_size($1) / (GREATEST(current_setting('block_size')::integer, 1)))
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)::bigint AS count
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FROM pg_class WHERE relname = $2;
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SQL
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# Computes an estimated count of the number of rows using stats collected by VACUUM
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# inspired by <https://www.citusdata.com/blog/2016/10/12/count-performance/#dup_counts_estimated_full>
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# and <https://stackoverflow.com/a/48391562/4186181>
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def self.estimated_count
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query_name = "SQL COUNT ESTIMATE: #{table_name}"
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table_name_attr = ActiveRecord::Relation::QueryAttribute.new(
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"relname", table_name, ActiveRecord::Type::String.new
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)
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result = connection.exec_query(
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QUERY_ESTIMATED_COUNT, query_name, [table_name_attr, table_name_attr]
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)
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result.first["count"]
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end
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end
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