Class: Shiba::Parsers::MysqlSelectFields

Inherits:
Object
  • Object
show all
Defined in:
lib/shiba/parsers/mysql_select_fields.rb

Overview

Extracts table name and columns from queries formatted by ‘show warnings’.

Constant Summary collapse

BACKTICK = 
"`"

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(sql) ⇒ MysqlSelectFields

Returns a new instance of MysqlSelectFields.



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# File 'lib/shiba/parsers/mysql_select_fields.rb', line 7

def initialize(sql)
  @sql = sql
  @sc = ShibaStringScanner.new(@sql)
end

Instance Attribute Details

#sc ⇒ Object (readonly)

Returns the value of attribute sc.



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# File 'lib/shiba/parsers/mysql_select_fields.rb', line 11

def sc
  @sc
end

Instance Method Details

#parse_fields ⇒ Object 



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# File 'lib/shiba/parsers/mysql_select_fields.rb', line 19

def parse_fields
  tables = {}

  sc.scan(%r{/\*.*?\*/ select })

  while !sc.scan(/ from/i)
    sc.scan(/distinct /)

    if sc.scan(/\w+\(/)
      parens = 1
      while parens > 0
        case sc.getch
        when '('
          parens += 1
        when ')'
          parens -= 1
        end
      end
      sc.scan(/ AS /)
      tick_match
      # parse function
    elsif sc.scan(/`(.*?)`\.`(.*?)`\.`(.*?)` AS `(.*?)`/)
      db = sc[1]
      table = sc[2]
      col = sc[3]

      tables[table] ||= []
      tables[table] << col

    elsif sc.scan(/`(.*?)`\.`(.*?)` AS `(.*?)`/)
      table = sc[1]
      col = sc[2]

      tables[table] ||= []
      tables[table] << col
    elsif sc.scan(/\(`(.*?)`\.`(.*?)` collate \w+\) AS `(.*?)`/)
      table = sc[1]
      col = sc[2]

      tables[table] ||= []
      tables[table] << col
    elsif sc.scan(/(\d+|NULL|'.*?') AS `(.*?)`/m)
    else
      if ENV['SHIBA_DEBUG']
        raise Shiba::Error.new("unknown stuff: in #{@sql}: #{@sc.rest}")
      end
      return {}
    end

    sc.scan(/,/)
  end

  # resolve table aliases
  if sc.scan(/ `.*?`\.`(.*?)` `(.*?)`/)
    table       = sc[1]
    table_alias = sc[2]

    if tables[table_alias]
      tables[table] = tables[table_alias]
      tables.delete(table_alias)
    end
  end

  tables
end

#tick_match ⇒ Object 



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# File 'lib/shiba/parsers/mysql_select_fields.rb', line 15

def tick_match
  sc.match_quoted_double_escape(BACKTICK)
end