Class: Kasket::QueryParser

Inherits:
Object
  • Object
show all
Defined in:
lib/kasket/query_parser.rb

Constant Summary collapse

AND =

Examples: SELECT * FROM ‘users` WHERE (`users`.`id` = 2) SELECT * FROM `users` WHERE (`users`.`id` = 2) LIMIT 1 ’SELECT * FROM 'posts' WHERE ('posts'.'id' = 574019247) ‘

/\s+AND\s+/i.freeze
VALUE =

Matches: 123, ?, ‘123’, ‘12”3’

/'?(\d+|\?|(?:(?:[^']|''|\\')*))'?/.freeze

Instance Method Summary collapse

Constructor Details

#initialize(model_class) ⇒ QueryParser

Returns a new instance of QueryParser.



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# File 'lib/kasket/query_parser.rb', line 12

def initialize(model_class)
  @model_class = model_class

  @supported_query_pattern = /^select\s+(.+?)\s+from (?:`|")#{@model_class.table_name}(?:`|") where (.*?)(|\s+limit 1)\s*$/i

  @star_pattern = /^((`|")#{@model_class.table_name}\2\.)?\*$/
  # Matches: `users`.id, `users`.`id`, users.id, id
  @table_and_column_pattern = /(?:(?:`|")?#{@model_class.table_name}(?:`|")?\.)?(?:`|")?([a-zA-Z]\w*)(?:`|")?/
  # Matches: KEY = VALUE, (KEY = VALUE), ()(KEY = VALUE))
  @key_eq_value_pattern = /^[\(\s]*#{@table_and_column_pattern}\s+(=|IN)\s+#{VALUE}[\)\s]*$/
end

Instance Method Details

#parse(sql) ⇒ Hash|nil

Parses a SQL query to produce a kasket query

Parameters:

  • sql (String) —

    the sql query to parse

Returns:

  • (Hash|nil) —

    the kasket query, or nil if the sql query is not supported



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# File 'lib/kasket/query_parser.rb', line 29

def parse(sql)
  if match = @supported_query_pattern.match(sql)
    select = match[1]
    unless @star_pattern.match? select
      # If we're not selecting all columns using star, then ensure all columns are selected explicitly
      select_columns = select.split(/\s*,\s*/).map do |s|
        break unless column_match = @table_and_column_pattern.match(s)

        column_match[1]
      end.uniq
      columns = @model_class.column_names
      return unless columns.size == select_columns.size && (columns - select_columns).empty?
    end
    where = match[2]
    limit = match[3]

    query = {}
    query[:attributes] = sorted_attribute_value_pairs(where)
    return if query[:attributes].nil?

    if query[:attributes].size > 1 && query[:attributes].map(&:last).any?(Array)
      # this is a query with IN conditions AND other conditions
      return
    end

    query[:index] = query[:attributes].map(&:first)
    query[:limit] = limit.blank? ? nil : 1
    query[:key] = @model_class.kasket_key_for(query[:attributes])
    query[:key] << '/first' if query[:limit] == 1 && !query[:index].include?(:id)
    query
  end
end