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# frozen_string_literal: true
module Arel # :nodoc: all
module Visitors
class MySQL < Arel::Visitors::ToSql
private
def visit_Arel_Nodes_Bin(o, collector)
collector << "BINARY "
visit o.expr, collector
end
def visit_Arel_Nodes_UnqualifiedColumn(o, collector)
visit o.expr, collector
end
###
# :'(
# http://dev.mysql.com/doc/refman/5.0/en/select.html#id3482214
def visit_Arel_Nodes_SelectStatement(o, collector)
if o.offset && !o.limit
o.limit = Arel::Nodes::Limit.new(18446744073709551615)
end
super
end
def visit_Arel_Nodes_SelectCore(o, collector)
o.froms ||= Arel.sql("DUAL")
super
end
def visit_Arel_Nodes_Concat(o, collector)
collector << " CONCAT("
visit o.left, collector
collector << ", "
visit o.right, collector
collector << ") "
collector
end
def visit_Arel_Nodes_IsNotDistinctFrom(o, collector)
collector = visit o.left, collector
collector << " <=> "
visit o.right, collector
end
def visit_Arel_Nodes_IsDistinctFrom(o, collector)
collector << "NOT "
visit_Arel_Nodes_IsNotDistinctFrom o, collector
end
# In the simple case, MySQL allows us to place JOINs directly into the UPDATE
# query. However, this does not allow for LIMIT, OFFSET and ORDER. To support
# these, we must use a subquery.
def prepare_update_statement(o)
if o.offset || has_join_sources?(o) && has_limit_or_offset_or_orders?(o)
super
else
o
end
end
alias :prepare_delete_statement :prepare_update_statement
# MySQL is too stupid to create a temporary table for use subquery, so we have
# to give it some prompting in the form of a subsubquery.
def build_subselect(key, o)
subselect = super
# Materialize subquery by adding distinct
# to work with MySQL 5.7.6 which sets optimizer_switch='derived_merge=on'
unless has_limit_or_offset_or_orders?(subselect)
core = subselect.cores.last
core.set_quantifier = Arel::Nodes::Distinct.new
end
Nodes::SelectStatement.new.tap do |stmt|
core = stmt.cores.last
core.froms = Nodes::Grouping.new(subselect).as("__active_record_temp")
core.projections = [Arel.sql(quote_column_name(key.name))]
end
end
end
end
end
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