Module: ArJdbc::MsSQL::LimitHelpers::SqlServerReplaceLimitOffset

Included in:
Arel::Visitors::SQLServer
Defined in:
lib/arjdbc/mssql/limit_helpers.rb

Class Method Summary collapse

Class Method Details

.replace_limit_offset!(sql, limit, offset, order) ⇒ Object



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# File 'lib/arjdbc/mssql/limit_helpers.rb', line 63

def replace_limit_offset!(sql, limit, offset, order)
  if limit
    offset ||= 0
    start_row = offset + 1
    end_row = offset + limit.to_i
    find_select = /\b(SELECT(?:\s+DISTINCT)?)\b(.*)/im
    whole, select, rest_of_query = find_select.match(sql).to_a
    if rest_of_query.strip!.first == '*'
      from_table = /.*FROM\s*\b(\w*)\b/i.match(rest_of_query).to_a[1]
    end
    new_sql = "#{select} t.* FROM (SELECT ROW_NUMBER() OVER(#{order}) AS _row_num, #{from_table + '.' if from_table}#{rest_of_query}"
    new_sql << ") AS t WHERE t._row_num BETWEEN #{start_row.to_s} AND #{end_row.to_s}"
    sql.replace(new_sql)
  end
  sql
end