124 lines
3.3 KiB
Ruby
124 lines
3.3 KiB
Ruby
# frozen_string_literal: true
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module Arel
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module Visitors
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class MSSQL < Arel::Visitors::ToSql
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RowNumber = Struct.new :children
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def initialize(*)
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@primary_keys = {}
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super
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end
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private
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# `top` wouldn't really work here. I.e. User.select("distinct first_name").limit(10) would generate
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# "select top 10 distinct first_name from users", which is invalid query! it should be
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# "select distinct top 10 first_name from users"
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def visit_Arel_Nodes_Top o
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""
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end
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def visit_Arel_Visitors_MSSQL_RowNumber o, collector
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collector << "ROW_NUMBER() OVER (ORDER BY "
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inject_join(o.children, collector, ', ') << ") as _row_num"
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end
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def visit_Arel_Nodes_SelectStatement o, collector
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if !o.limit && !o.offset
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return super
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end
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is_select_count = false
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o.cores.each { |x|
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core_order_by = row_num_literal determine_order_by(o.orders, x)
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if select_count? x
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x.projections = [core_order_by]
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is_select_count = true
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else
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x.projections << core_order_by
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end
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}
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if is_select_count
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# fixme count distinct wouldn't work with limit or offset
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collector << "SELECT COUNT(1) as count_id FROM ("
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end
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collector << "SELECT _t.* FROM ("
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collector = o.cores.inject(collector) { |c,x|
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visit_Arel_Nodes_SelectCore x, c
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}
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collector << ") as _t WHERE #{get_offset_limit_clause(o)}"
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if is_select_count
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collector << ") AS subquery"
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else
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collector
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end
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end
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def get_offset_limit_clause o
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first_row = o.offset ? o.offset.expr.to_i + 1 : 1
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last_row = o.limit ? o.limit.expr.to_i - 1 + first_row : nil
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if last_row
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" _row_num BETWEEN #{first_row} AND #{last_row}"
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else
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" _row_num >= #{first_row}"
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end
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end
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def visit_Arel_Nodes_DeleteStatement o, collector
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collector << 'DELETE '
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if o.limit
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collector << 'TOP ('
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visit o.limit.expr, collector
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collector << ') '
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end
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collector << 'FROM '
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collector = visit o.relation, collector
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if o.wheres.any?
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collector << ' WHERE '
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inject_join o.wheres, collector, AND
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else
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collector
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end
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end
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def determine_order_by orders, x
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if orders.any?
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orders
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elsif x.groups.any?
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x.groups
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else
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pk = find_left_table_pk(x.froms)
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pk ? [pk] : []
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end
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end
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def row_num_literal order_by
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RowNumber.new order_by
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end
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def select_count? x
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x.projections.length == 1 && Arel::Nodes::Count === x.projections.first
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end
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# FIXME raise exception of there is no pk?
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def find_left_table_pk o
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if o.kind_of?(Arel::Nodes::Join)
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find_left_table_pk(o.left)
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elsif o.instance_of?(Arel::Table)
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find_primary_key(o)
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end
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end
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def find_primary_key(o)
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@primary_keys[o.name] ||= begin
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primary_key_name = @connection.primary_key(o.name)
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# some tables might be without primary key
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primary_key_name && o[primary_key_name]
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end
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end
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end
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end
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end
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