Class: Graffiti::SquishQuery

Inherits:
Object
  • Object
show all
Includes:
Debug
Defined in:
lib/graffiti/squish.rb

Overview

parse Squish query and translate triples to relational conditions

provides access to internal representation of the parsed query and utility functions to deal with Squish syntax

Direct Known Subclasses

SquishAssert, SquishSelect

Constant Summary collapse

INTERNAL =

regexp for internal resource reference

Regexp.new(/\A([[:digit:]]+)\z/).freeze
BN =

regexp for blank node mark and name

Regexp.new(/\A\?([[:alnum:]_]+)\z/).freeze
BN_SCAN =

regexp for scanning blank nodes inside a string

Regexp.new(/\?[[:alnum:]_]+?\b/).freeze
PARAMETER =

regexp for parametrized value

Regexp.new(/\A:([[:alnum:]_]+)\z/).freeze
LITERAL =

regexp for replaced string literal

Regexp.new(/\A'(\d+)'\z/).freeze
LITERAL_SCAN =

regexp for scanning replaced string literals in a string

Regexp.new(/'(\d+)'/).freeze
PARAMETER_AND_LITERAL_SCAN =

regexp for scanning query parameters inside a string

Regexp.new(/\B:([[:alnum:]_]+)|'(\d+)'/).freeze
NUMBER =

regexp for number

Regexp.new(/\A-?[[:digit:]]+(\.[[:digit:]]+)?\z/).freeze
OPERATOR =

regexp for operator

Regexp.new(/\A(\+|-|\*|\/|\|\||<|<=|>|>=|=|!=|@@|to_tsvector|to_tsquery|I?LIKE|NOT|AND|OR|IN|IS|NULL)\z/i).freeze
AGGREGATE =

regexp for aggregate function

Regexp.new(/\A(avg|count|max|min|sum)\z/i).freeze
QUERY = 
Regexp.new(/\A\s*(SELECT|INSERT|UPDATE)\b\s*(.*?)\s*
\bWHERE\b\s*(.*?)\s*
(?:\bEXCEPT\b\s*(.*?))?\s*
(?:\bOPTIONAL\b\s*(.*?))?\s*
(?:\bLITERAL\b\s*(.*?))?\s*
(?:\bGROUP\s+BY\b\s*(.*?))?\s*
(?:\bORDER\s+BY\b\s*(.*?)\s*(ASC|DESC)?)?\s*
(?:\bUSING\b\s*(.*?))?\s*\z/mix).freeze

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(config, query) ⇒ SquishQuery

extract common Squish query sections, perform namespace substitution, generate query pattern graph, call transform_pattern, determine query type and parse nodes section accordingly



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# File 'lib/graffiti/squish.rb', line 71

def initialize(config, query)
  query.nil? and raise ProgrammingError, "SquishQuery: query can't be nil"
  if query.kind_of? Hash   # pre-parsed query (used by SquishAssert)
    @nodes = query[:nodes]
    @pattern = query[:pattern]
    @negative = query[:negative]
    @optional = query[:optional]
    @strings = query[:strings]
    @literal = @group = @order = ''
    @sql_mapper = SqlMapper.new(config, @pattern)
    return self
  elsif not query.kind_of? String
    raise ProgrammingError,
      "Bad query initialization parameter class: #{query.class}"
  end

  debug { 'SquishQuery ' + query }
  @query = query   # keep original string
  query = query.dup

  # replace string literals with 'n' placeholders (also see #substitute_literals)
  @strings = []
  query.gsub!(/'((?:''|[^'])*)'/m) do
    @strings.push $1.gsub("''", "'")   # keep unescaped string
    "'" + (@strings.size - 1).to_s + "'"
  end

  match = QUERY.match(query) or raise ProgrammingError,
    "Malformed query: are keywords SELECT, INSERT, UPDATE or WHERE missing?"
  match, @key, @nodes, @pattern, @negative, @optional, @literal,
    @group, @order, @order_dir, @ns = match.to_a.collect {|m| m.to_s }
  match = nil
  @key.upcase!
  @order_dir.upcase!

  # namespaces
  # todo: validate ns
  @ns = (@ns.empty? or /\APRESET\s+NS\z/ =~ @ns) ? config.ns :
    Hash[*@ns.gsub(/\b(FOR|AS|AND)\b/i, '').scan(/\S+/)]
  @pattern = parse_pattern(@pattern)
  @optional = parse_pattern(@optional)
  @negative = parse_pattern(@negative)

  # validate SQL expressions
  validate_expression(@literal)
  @group.split(/\s*,\s*/).each {|group| validate_expression(group) }
  validate_expression(@order)

  @sql_mapper = SqlMapper.new(
    config, @pattern, @negative, @optional, @literal)

  # check that all variables can be bound
  @variables = query.scan(BN_SCAN)
  @variables.each {|node| @sql_mapper.bind(node) }

  return self
end

Instance Attribute Details

#group ⇒ Object (readonly)

SQL GROUP BY expression



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# File 'lib/graffiti/squish.rb', line 139

def group
  @group
end

#literal ⇒ Object (readonly)

literal SQL expression



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# File 'lib/graffiti/squish.rb', line 136

def literal
  @literal
end

#nodes ⇒ Object (readonly)

blank variables control section



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# File 'lib/graffiti/squish.rb', line 130

def nodes
  @nodes
end

#ns ⇒ Object (readonly)

query namespaces mapping



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# File 'lib/graffiti/squish.rb', line 148

def ns
  @ns
end

#order ⇒ Object (readonly)

SQL order expression



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# File 'lib/graffiti/squish.rb', line 142

def order
  @order
end

#order_dir ⇒ Object (readonly)

direction of order, ASC or DESC



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# File 'lib/graffiti/squish.rb', line 145

def order_dir
  @order_dir
end

#pattern ⇒ Object (readonly)

query pattern graph as array of triples [ [p, s, o], … ]



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# File 'lib/graffiti/squish.rb', line 133

def pattern
  @pattern
end

#variables ⇒ Object (readonly)

list of variables defined in the query



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# File 'lib/graffiti/squish.rb', line 151

def variables
  @variables
end

Class Method Details

.ns_shrink(uriref, namespaces) ⇒ Object

replace schema uri with a prefix from a supplied namespaces hash



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# File 'lib/graffiti/squish.rb', line 176

def SquishQuery.ns_shrink(uriref, namespaces)
  u = uriref.dup or return nil
  namespaces.each {|p, uri| SquishQuery.uri_shrink!(u, p, uri) and break }
  return u
end

.uri_shrink!(uriref, prefix, uri) ⇒ Object

replace schema uri with namespace prefix



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# File 'lib/graffiti/squish.rb', line 170

def SquishQuery.uri_shrink!(uriref, prefix, uri)
  uriref.gsub!(/\A#{uri}([^\/#]+)\z/) {"#{prefix}::#{$1}"}
end

Instance Method Details

#ns_shrink(uriref) ⇒ Object

replace schema uri with a prefix from query namespaces



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# File 'lib/graffiti/squish.rb', line 184

def ns_shrink(uriref)
  SquishQuery.ns_shrink(uriref, @ns)
end

#substitute_literals(s) ⇒ Object

replace ‘n’ substitutions with query string literals (see #new, #LITERAL)



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# File 'lib/graffiti/squish.rb', line 161

def substitute_literals(s)
  return s unless s.kind_of? String
  s.gsub(LITERAL_SCAN) do
    get_literal_value($1.to_i)
  end
end

#to_s ⇒ Object

returns original string passed in for parsing



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# File 'lib/graffiti/squish.rb', line 155

def to_s
  @query
end

#validate_expression(string) ⇒ Object

validate expression

expression := value [ operator expression ]

value := blank_node | literal_string | number | ‘(’ expression ‘)’

whitespace between tokens (except inside parentheses) is mandatory



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# File 'lib/graffiti/squish.rb', line 196

def validate_expression(string)
  # todo: lexical analyser
  string.split(/[\s(),]+/).each do |token|
    case token
    when '', BN, PARAMETER, LITERAL, NUMBER, OPERATOR, AGGREGATE
    else
      raise ProgrammingError, "Bad token '#{token}' in expression"
    end
  end
  string
end