Module: FastCount::Extensions::ModelExtension

Defined in:
lib/fast_count/extensions.rb

Instance Method Summary collapse

Instance Method Details

#fast_count(threshold: FastCount.threshold) ⇒ Object

Returns an estimated number of rows in the table. Runs in milliseconds.

Examples:

User.fast_count
User.fast_count(threshold: 50_000)


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# File 'lib/fast_count/extensions.rb', line 13

def fast_count(threshold: FastCount.threshold)
  adapter = Adapters.for_connection(connection)
  adapter.fast_count(table_name, threshold)
end

#fast_distinct_count(column:) ⇒ Object

Returns an exact number of distinct values in a column. It is suited for cases, when there is a small amount of distinct values in a column compared to a total number of values (for example, 10M rows total and 500 distinct values).

Runs orders of magnitude faster than ‘SELECT COUNT(DISTINCT column) …’.

Note: You need to have an index starting with the specified column for this to work.

Uses an “Loose Index Scan” technique (see wiki.postgresql.org/wiki/Loose_indexscan).

Examples:

User.fast_distinct_count(column: :company_id)


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# File 'lib/fast_count/extensions.rb', line 33

def fast_distinct_count(column:)
  if column.to_s == primary_key
    raise "Use `#fast_count` when counting primary keys."
  end

  adapter = Adapters.for_connection(connection)
  adapter.fast_distinct_count(table_name, column)
end