82 lines
2.5 KiB
Ruby
82 lines
2.5 KiB
Ruby
|
module EachBatch
|
||
|
|
extend ActiveSupport::Concern
|
||
|
|
|
||
|
|
module ClassMethods
|
||
|
|
# Iterates over the rows in a relation in batches, similar to Rails'
|
||
|
|
# `in_batches` but in a more efficient way.
|
||
|
|
#
|
||
|
|
# Unlike `in_batches` provided by Rails this method does not support a
|
||
|
|
# custom start/end range, nor does it provide support for the `load:`
|
||
|
|
# keyword argument.
|
||
|
|
#
|
||
|
|
# This method will yield an ActiveRecord::Relation to the supplied block, or
|
||
|
|
# return an Enumerator if no block is given.
|
||
|
|
#
|
||
|
|
# Example:
|
||
|
|
#
|
||
|
|
# User.each_batch do |relation|
|
||
|
|
# relation.update_all(updated_at: Time.now)
|
||
|
|
# end
|
||
|
|
#
|
||
|
|
# The supplied block is also passed an optional batch index:
|
||
|
|
#
|
||
|
|
# User.each_batch do |relation, index|
|
||
|
|
# puts index # => 1, 2, 3, ...
|
||
|
|
# end
|
||
|
|
#
|
||
|
|
# You can also specify an alternative column to use for ordering the rows:
|
||
|
|
#
|
||
|
|
# User.each_batch(column: :created_at) do |relation|
|
||
|
|
# ...
|
||
|
|
# end
|
||
|
|
#
|
||
|
|
# This will produce SQL queries along the lines of:
|
||
|
|
#
|
||
|
|
# User Load (0.7ms) SELECT "users"."id" FROM "users" WHERE ("users"."id" >= 41654) ORDER BY "users"."id" ASC LIMIT 1 OFFSET 1000
|
||
|
|
# (0.7ms) SELECT COUNT(*) FROM "users" WHERE ("users"."id" >= 41654) AND ("users"."id" < 42687)
|
||
|
|
#
|
||
|
|
# of - The number of rows to retrieve per batch.
|
||
|
|
# column - The column to use for ordering the batches.
|
||
|
|
def each_batch(of: 1000, column: primary_key)
|
||
|
|
unless column
|
||
|
|
raise ArgumentError,
|
||
|
|
'the column: argument must be set to a column name to use for ordering rows'
|
||
|
|
end
|
||
|
|
|
||
|
|
start = except(:select)
|
||
|
|
.select(column)
|
||
|
|
.reorder(column => :asc)
|
||
|
|
.take
|
||
|
|
|
||
|
|
return unless start
|
||
|
|
|
||
|
|
start_id = start[column]
|
||
|
|
arel_table = self.arel_table
|
||
|
|
|
||
|
|
1.step do |index|
|
||
|
|
stop = except(:select)
|
||
|
|
.select(column)
|
||
|
|
.where(arel_table[column].gteq(start_id))
|
||
|
|
.reorder(column => :asc)
|
||
|
|
.offset(of)
|
||
|
|
.limit(1)
|
||
|
|
.take
|
||
|
|
|
||
|
|
relation = where(arel_table[column].gteq(start_id))
|
||
|
|
|
||
|
|
if stop
|
||
|
|
stop_id = stop[column]
|
||
|
|
start_id = stop_id
|
||
|
|
relation = relation.where(arel_table[column].lt(stop_id))
|
||
|
|
end
|
||
|
|
|
||
|
|
# Any ORDER BYs are useless for this relation and can lead to less
|
||
|
|
# efficient UPDATE queries, hence we get rid of it.
|
||
|
|
yield relation.except(:order), index
|
||
|
|
|
||
|
|
break unless stop
|
||
|
|
end
|
||
|
|
end
|
||
|
|
end
|
||
|
|
end
|