A DSL to make it easy to integrate other apps to Neo4J applications.

This module provide a clean API to build queries using CYPHER query language, which is largely used by Neo4j

Usage:

First of all, add import ExCpyher to the top of your module, so that cypher macro is available to your functions, then you can run it to generate you cypher queries.

Examples:

MATCH statements:

1. Matching nodes without returning a specific property

  iex> cypher do: match(node(:n))
  "MATCH (n)"

  iex> cypher do: match(node(:p, [:Person]))
  "MATCH (p:Person)"

  iex> cypher do
  ...>   match(node(:p, [:Person], %{name: "bob"}))
  ...> end
  ~S[MATCH (p:Person {"name":"bob"})]

We already support associations too:

  iex> cypher do
  ...>   match node(:p, [:Person]) -- node(:c, [:Company])
  ...> end
  "MATCH (p:Person)--(c:Company)"

  iex> cypher do
  ...>   match node(:p, [:Person]) -- rel(:WORKS_IN) -- node(:c, [:Company])
  ...>   return :p
  ...> end
  "MATCH (p:Person)-[WORKS_IN]-(c:Company) RETURN p"

Can use arrow-syntax to represent directed associations, but must use parenthesis arround the match arguments so that elixir correctly builds the AST with the correct precedence structure

  iex> cypher do
  ...>   match (node(:p, [:Person]) -- rel(:WORKS_IN) -> node(:c, [:Company]))
  ...> end
  "MATCH (p:Person)-[WORKS_IN]->(c:Company)"

  iex> cypher do
  ...>   match (node(:c, [:Company]) <- rel(:WORKS_IN) -- node(:p, [:Person]))
  ...> end
  "MATCH (c:Company)<-[WORKS_IN]-(p:Person)"

ORDERing and LIMITing queries:

You can order and/or limit your query results with order and limit commands:

  iex> cypher do
  ...>   match node(:s, [:Sharks])
  ...>   order s.name
  ...>   limit 10
  ...>   return s.name, s.population
  ...> end
  "MATCH (s:Sharks) ORDER BY s.name LIMIT 10 RETURN s.name, s.population"

Also, you can choose the ordering direction of your matched nodes with a tuple syntax:

  iex> cypher do
  ...>   match node(:s, [:Sharks])
  ...>   order {s.name, :asc}, {s.age, :desc}
  ...>   return :s
  ...> end
  "MATCH (s:Sharks) ORDER BY s.name ASC, s.age DESC RETURN s"

CREATE and MERGE stuff

In order to create new nodes into your database, you can use the following syntax:

  iex> cypher do
  ...>   create node(:p, [:Player], %{nick: "like4boss", score: "100"})
  ...>   return p.name
  ...> end
  ~S[CREATE (p:Player {"nick":"like4boss","score":"100"}) RETURN p.name]

However, if you want to match pre-existing nodes instead of creating new ones, you can use merge, as follows:

  iex> cypher do
  ...>   merge node(:p, [:Player], %{nick: "like4boss"})
  ...>   merge node(:p2, [:Player], %{nick: "marioboss"})
  ...>   return p.name
  ...> end
  ~S|MERGE (p:Player {"nick":"like4boss"}) MERGE (p2:Player {"nick":"marioboss"}) RETURN p.name|

  iex> cypher do
  ...>   merge node(:p, [:Player], %{nick: "like4boss"})
  ...>   merge node(:p2, [:Player], %{nick: "marioboss"})
  ...>   merge (node(:p) -- rel([:IN_LOBBY]) -> node(:p2))
  ...>   return p.name
  ...> end
  ~S|MERGE (p:Player {"nick":"like4boss"}) MERGE (p2:Player {"nick":"marioboss"}) MERGE (p)-[:IN_LOBBY]->(p2) RETURN p.name|