23 lines
871 B
Ruby
23 lines
871 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(?) / (GREATEST(current_setting('block_size')::integer, 1)))
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)::bigint AS count
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FROM pg_class WHERE relname = ?;
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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 = sanitize_sql_array([QUERY_ESTIMATED_COUNT, table_name, table_name])
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result = connection.execute(query)
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count = result.first["count"]
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result.clear # PG::Result is manually managed in memory, we need to release its resources
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count
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end
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end
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