Class: HumanQL::PostgreSQLGenerator

Inherits:
Object
  • Object
show all
Defined in:
lib/human-ql/postgresql_generator.rb

Overview

Generate query strings suitable for passing to PostgreSQL’s to_tsquery function, from a HumanQL abstract syntax tree (AST).

In order to guarantee valid output for any human input, the AST should be created using PostgreSQLCustomParser and normalized via TreeNormalizer (with minimal defaults).

Any scope’s provided in the parser should have been handled and stripped out of the AST, as PostgreSQL is not expected to have a direct equivalent in tsquery syntax.

Constant Summary collapse

AND =

– From www.postgresql.org/docs/9.6/static/datatype-textsearch.html > In the absence of parentheses, ‘!’ (NOT) binds most tightly, > and ‘&’ (AND) and ‘<->’ (FOLLOWED BY) both bind more tightly > than | (OR). ++

' & '.freeze
OR = 
' | '.freeze
NOT = 
'!'.freeze
NEAR = 
' <-> '.freeze

Instance Method Summary collapse

Instance Method Details

#generate(node) ⇒ Object

Given the root node of the AST, return a string in PostgreSQL tsquery syntax.



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# File 'lib/human-ql/postgresql_generator.rb', line 45

def generate( node )
  op,*args = node
  if ! node.is_a?( Array )
    op
  elsif args.empty?
    nil
  else
    case op
    when :and
      terms_join( args, AND )
    when :or
      pwrap( terms_join( args, OR ) )
    when :not
      if args[0].is_a?( Array )
        NOT + pwrap( generate( args[0] ) )
      else
        NOT + args[0]
      end
    when :phrase
      terms_join( args, NEAR )
    else
      raise "Unsupported op: #{node.inspect}"
    end
  end
end