Parser

Grammar

We use the same grammar as open cypher but remove features that are not yet supported. See issue#57 for a list of features that are currently removed.

Parser

Parser class structure closely follows open cypher grammar.

Graph Pattern

• NodePattern: (a:Person)
  • name, type
• RelPattern: -[e1:knows]->
  • name, label, direction
• PatternElementChain: -[e1:knows]->(b:Student)
  • relPattern, nodePattern
• PatternElement: (a:Person) -[e1:knows]->(b:Student) -[e2]->(c)
  • nodePattern, vector<PatternElementChain>
• MatchStatement: MATCH ..., ...
  • vector<PatternElement>
• SingleQuery MATCH ... MATCH ...
  • vector<MatchStatement>

Expressions

• Boolean Connection
  • AND, XOR, OR, NOT
• Comparison
  • = , <>, >, <, >=, <=
• Arithmetic
  • +, - , *, /, %, ^
• String Operator
  • STARTS WITH, ENDS WITH, CONTAINS
• Null Operator
  • IS NULL, IS NOT NULL
• Property
  • e.g. a.name
• Function Invocation
  • functionName(param1, param2, ..)
• Parenthesized Expression Support
  • (a.isStudent AND a.isMale) OR a.name CONTAINS "Xiyang"
• Variable (Leaf Expression)
• Literal (Leaf Expression)
  • INT, DOUBLE, BOOLEAN, STRING, NULL

Class Structure

• Every expression is represented as ParsedExpression with 3 attributes
  • ExpressionType
  • string text (used to store content for LiteralExpression, VaraibleName, FunctionName and PropertyName)
  • vector<ParsedExpression> children (empty for leaf expression)