1. Cypher: Como a query
language do Neo4j foi
construída e como usá-la
tldr: Cypher internals em 15 minutos

2. Quem é vc?

3. Quem é vc?
Adriano Almeida
@adrianoalmeida7
ahalmeida.com

4. Quem é vc?
Adriano Almeida
@adrianoalmeida7
ahalmeida.com

5. Quem é vc?
Adriano Almeida
@adrianoalmeida7
ahalmeida.com

6. Quem é vc?
Adriano Almeida
@adrianoalmeida7
ahalmeida.com

7. Buscando dados no Neo4j

8. Buscando dados no Neo4j
1. Traverse API Clássica

9. Buscando dados no Neo4j
1. Traverse API Clássica
private static Traverser quemCodouOMatrix(final Node startNode) {
return startNode.traverse(Order.BREADTH_FIRST,
StopEvaluator.END_OF_GRAPH, new ReturnableEvaluator() {
@Override
public boolean isReturnableNode(final TraversalPosition currentPos) {
return !currentPos.isStartNode()
&& currentPos.lastRelationshipTraversed().isType(RelTypes.CODED_BY);
}
}, RelTypes.CODED_BY, Direction.OUTGOING, RelTypes.KNOWS,
Direction.OUTGOING
);
}

10. Buscando dados no Neo4j
2. Traverse API Nova

11. Buscando dados no Neo4j
2. Traverse API Nova
private static Traverser quemCodouOMatrix( final Node startNode )
{
TraversalDescription td = Traversal.description()
.breadthFirst()
.relationships( RelTypes.CODED_BY, Direction.OUTGOING )
.relationships( RelTypes.KNOWS, Direction.OUTGOING )
.evaluator(
Evaluators.returnWhereLastRelationshipTypeIs( RelTypes.CODED_BY ) );
return td.traverse( startNode );
}

12. Buscando dados no Neo4j
3. Cypher

13. Buscando dados no Neo4j
3. Cypher
start programmer=(3)
match (programmer)-[:PAIRED]->(pair)
where pair.age > 30
return pair
order by pair.age
skip 5 limit 10

14. Buscando dados no Neo4j
3. Cypher
private static Iterator<Node> comQuemUmDevPareou()
{
ExecutionEngine engine = new ExecutionEngine(db);
ExecutionResult result = engine.execute( "start programmer=(3) " +
"match (programmer)-[:PAIRED]->(pair) where pair.age > 30 " +
"return pair " +
"order by pair.age " +
"skip 5 limit 10" );
Iterator<Node> pairs = result.columnAs( "pair" );
return pairs;
}

15. Buscando dados no Neo4j
3. Cypher
- Parsing
- Execução

16. Definindo a linguagem
Start
Match start programmer=(3)
match (programmer)-[:PAIRED]->(pair)
Where where pair.age > 30
Return return pair
order by pair.age
Order By skip 5 limit 10
Skip & Limit

17. Por partes: Start Clause
start ::= "start" {"," nodeByIds | nodeByIndex | nodeByIndexQuery |
relsByIds | relsByIndex }
nodeByIds ::= identity "=" "(" {"," number} ")"
nodeByIndex ::= identity "=" "(" identity "," identity "," string ")"
nodeByIndexQuery ::= identity "=" "(" identity "," string ")"
relsByIds ::= identity "=" "<" { "," number } ">"
relsByIndex ::= identity "=" "<" identity "," identity "," string ">"

18. Por partes: Start Clause
Como implementar o parser disso?

19. Por partes: Start Clause
Scala + Parser Combinators

20. Por partes: Start Clause
package org.neo4j.cypher.parser
trait StartClause extends JavaTokenParsers with Tokens {
def start: Parser[Start] = ignoreCase("start") ~> rep1sep(nodeByIds | nodeByIndex | nodeByIndexQuery |
relsByIds | relsByIndex, ",") ^^ (Start(_: _*))
def nodeByIds = identity ~ "=" ~ "(" ~ rep1sep(wholeNumber, ",") ~ ")" ^^ {
case varName ~ "=" ~ "(" ~ id ~ ")" => NodeById(varName, id.map(_.toLong).toSeq: _*)
}
def nodeByIndex = identity ~ "=" ~ "(" ~ identity ~ "," ~ identity ~ "," ~ string ~ ")" ^^ {
case varName ~ "=" ~ "(" ~ index ~ "," ~ key ~ "," ~ value ~ ")" => NodeByIndex(varName, index, key, value)
}
def nodeByIndexQuery = identity ~ "=" ~ "(" ~ identity ~ "," ~ string ~ ")" ^^ {
case varName ~ "=" ~ "(" ~ index ~ "," ~ query ~ ")" => NodeByIndexQuery(varName, index, query)
}
def relsByIds = identity ~ "=" ~ "<" ~ rep1sep(wholeNumber, ",") ~ ">" ^^ {
case varName ~ "=" ~ "<" ~ id ~ ">" => RelationshipById(varName, id.map(_.toLong).toSeq: _*)
}
def relsByIndex = identity ~ "=" ~ "<" ~ identity ~ "," ~ identity ~ "," ~ string ~ ">" ^^ {
case varName ~ "=" ~ "<" ~ index ~ "," ~ key ~ "," ~ value ~ ">" => RelationshipByIndex(varName, index, key,
value)
}
}

21. Por partes: Start Clause
package org.neo4j.cypher.parser
trait StartClause extends JavaTokenParsers with Tokens {
def start: Parser[Start] = ignoreCase("start") ~> rep1sep(nodeByIds | nodeByIndex | nodeByIndexQuery |
relsByIds | relsByIndex, ",") ^^ (Start(_: _*))
def nodeByIds = identity ~ "=" ~ "(" ~ rep1sep(wholeNumber, ",") ~ ")" ^^ {
case varName ~ "=" ~ "(" ~ id ~ ")" => NodeById(varName, id.map(_.toLong).toSeq: _*)
}
def nodeByIndex = identity ~ "=" ~ "(" ~ identity ~ "," ~ identity ~ "," ~ string ~ ")" ^^ {
case varName ~ "=" ~ "(" ~ index ~ "," ~ key ~ "," ~ value ~ ")" => NodeByIndex(varName, index, key, value)
}
def nodeByIndexQuery = identity ~ "=" ~ "(" ~ identity ~ "," ~ string ~ ")" ^^ {
case varName ~ "=" ~ "(" ~ index ~ "," ~ query ~ ")" => NodeByIndexQuery(varName, index, query)
}
def relsByIds = identity ~ "=" ~ "<" ~ rep1sep(wholeNumber, ",") ~ ">" ^^ {
case varName ~ "=" ~ "<" ~ id ~ ">" => RelationshipById(varName, id.map(_.toLong).toSeq: _*)
}
def relsByIndex = identity ~ "=" ~ "<" ~ identity ~ "," ~ identity ~ "," ~ string ~ ">" ^^ {
case varName ~ "=" ~ "<" ~ index ~ "," ~ key ~ "," ~ value ~ ">" => RelationshipByIndex(varName, index, key,
value)
}
}

22. Por partes: Start Clause
package org.neo4j.cypher.parser
trait StartClause extends JavaTokenParsers with Tokens {
def start: Parser[Start] = ignoreCase("start") ~> rep1sep(nodeByIds | nodeByIndex | nodeByIndexQuery |
relsByIds | relsByIndex, ",") ^^ (Start(_: _*))
def nodeByIds = identity ~ "=" ~ "(" ~ rep1sep(wholeNumber, ",") ~ ")" ^^ {
case varName ~ "=" ~ "(" ~ id ~ ")" => NodeById(varName, id.map(_.toLong).toSeq: _*)
}
def nodeByIndex = identity ~ "=" ~ "(" ~ identity ~ "," ~ identity ~ "," ~ string ~ ")" ^^ {
case varName ~ "=" ~ "(" ~ index ~ "," ~ key ~ "," ~ value ~ ")" => NodeByIndex(varName, index, key, value)
}
def nodeByIndexQuery = identity ~ "=" ~ "(" ~ identity ~ "," ~ string ~ ")" ^^ {
case varName ~ "=" ~ "(" ~ index ~ "," ~ query ~ ")" => NodeByIndexQuery(varName, index, query)
}
def relsByIds = identity ~ "=" ~ "<" ~ rep1sep(wholeNumber, ",") ~ ">" ^^ {
case varName ~ "=" ~ "<" ~ id ~ ">" => RelationshipById(varName, id.map(_.toLong).toSeq: _*)
}
def relsByIndex = identity ~ "=" ~ "<" ~ identity ~ "," ~ identity ~ "," ~ string ~ ">" ^^ {
case varName ~ "=" ~ "<" ~ index ~ "," ~ key ~ "," ~ value ~ ">" => RelationshipByIndex(varName, index, key,
value)
}
}

23. Por partes: Start Clause
package org.neo4j.cypher.parser
trait StartClause extends JavaTokenParsers with Tokens {
def start: Parser[Start] = ignoreCase("start") ~> rep1sep(nodeByIds | nodeByIndex | nodeByIndexQuery |
relsByIds | relsByIndex, ",") ^^ (Start(_: _*))
def nodeByIds = identity ~ "=" ~ "(" ~ rep1sep(wholeNumber, ",") ~ ")" ^^ {
case varName ~ "=" ~ "(" ~ id ~ ")" => NodeById(varName, id.map(_.toLong).toSeq: _*)
}
def nodeByIndex = identity ~ "=" ~ "(" ~ identity ~ "," ~ identity ~ "," ~ string ~ ")" ^^ {
case varName ~ "=" ~ "(" ~ index ~ "," ~ key ~ "," ~ value ~ ")" => NodeByIndex(varName, index, key, value)
}
def nodeByIndexQuery = identity ~ "=" ~ "(" ~ identity ~ "," ~ string ~ ")" ^^ {
case varName ~ "=" ~ "(" ~ index ~ "," ~ query ~ ")" => NodeByIndexQuery(varName, index, query)
}
def relsByIds = identity ~ "=" ~ "<" ~ rep1sep(wholeNumber, ",") ~ ">" ^^ {
case varName ~ "=" ~ "<" ~ id ~ ">" => RelationshipById(varName, id.map(_.toLong).toSeq: _*)
}
def relsByIndex = identity ~ "=" ~ "<" ~ identity ~ "," ~ identity ~ "," ~ string ~ ">" ^^ {
case varName ~ "=" ~ "<" ~ index ~ "," ~ key ~ "," ~ value ~ ">" => RelationshipByIndex(varName, index, key,
value)
}
}

24. AST
Query.scala
package org.neo4j.cypher.commands
case class Start(startItems: StartItem*)
StartItem.scala
package org.neo4j.cypher.commands
abstract sealed class StartItem(val variable:String)
abstract class NodeStartItem(varName:String) extends StartItem(varName)
case class NodeById(varName:String, id: Long*) extends NodeStartItem(varName)

25. Por partes: Outras Clauses
(não dá tempo)
http://chu.pe/8K

26. Toda a query
package org.neo4j.cypher.parser
class CypherParser extends JavaTokenParsers with StartClause with MatchClause with WhereClause
with ReturnClause with SkipLimitClause with OrderByClause with StringExtras {
def query: Parser[Query] = start ~ opt(matching) ~ opt(where) ~ returns ~ opt(order) ~ opt(skip) ~ opt(limit) ^^ {
case start ~ matching ~ where ~ returns ~ order ~ skip ~ limit => {
val slice = (skip,limit) match {
case (None,None) => None
case (s,l) => Some(Slice(s,l))
}
val (pattern:Option[Match], namedPaths:Option[NamedPaths]) = matching match {
case Some((p,NamedPaths())) => (Some(p),None)
case Some((Match(),nP)) => (None,Some(nP))
case Some((p,nP)) => (Some(p),Some(nP))
case None => (None,None)
}
Query(returns._1, start, pattern, where, returns._2, order, slice, namedPaths)
}
}

27. A execução
ExecutionEngine.scala
http://chu.pe/8N

28. Pipes
StartPipe

29. Pipes
StartPipe -> MatchPipe

30. Pipes
StartPipe -> MatchPipe -> NamedPathPipe

31. Pipes
StartPipe -> MatchPipe -> NamedPathPipe ->
FilterPipe

32. Pipes
StartPipe -> MatchPipe -> NamedPathPipe ->
FilterPipe -> TransformPipe (Aggregation, Sort & Slice)

33. Pipes
StartPipe -> MatchPipe -> NamedPathPipe ->
FilterPipe -> TransformPipe (Aggregation, Sort & Slice)
-> ColumnFilterPipe

35. Prós e Contras
+ Objetiva
+ Ops Friendly
+ Poderosa (algoritmos de grafos e pattern matching)
- Verbosa
- Performance (ainda)
+/- Work In Progress

36. Explicação mais
detalhada
• http://ahalmeida.com/

37. Disclaimer
Códigos da versão 1.4.2

38. Obrigado
@adrianoalmeida7