Data Modification Statements

queryBodyDeleteStmt := DELETE alias FROM pattern [whereClause]
pattern := (vertexPattern | edgePattern)

# Delete all "person" vertices with location equal to "us"
CREATE QUERY deleteEx() FOR GRAPH workNet {
  S = {person.*};
  DELETE s FROM S:s
    WHERE s.locationId == "us";
}

# Delete all "worksFor" edges where the person's location is "us"
CREATE QUERY deleteEx2() FOR GRAPH workNet {
  S = {person.*};
  DELETE e FROM S:s -(worksFor:e)- company:t
    WHERE s.locationId == "us";
}

CREATE QUERY countAtLocation(STRING loc) FOR GRAPH workNet {
  SetAccum<EDGE> @@selEdge;
  Start = {person.*};

  SV = SELECT s FROM Start:s
    WHERE s.locationId == loc;
  PRINT SV.size() AS numVertices;

  SE = SELECT s FROM Start:s -(worksFor:e)- company:t
    WHERE s.locationId == loc
    ACCUM @@selEdge += e;
  PRINT @@selEdge.size() AS numEdges;
}

dmlSubDeleteStmt := DELETE "(" alias ")"

# Remove any post vertices posted by the given user
CREATE QUERY deletePosts(vertex<person> seed) FOR GRAPH socialNet {
	start = {seed};

	# Best practice is to delete a vertex in a POST-ACCUM, which only
	# occurs once for each vertex v, guaranteeing that a vertex is not
	# deleted more than once
	postAccumDeletedPosts = SELECT v FROM start -(posted>:e)- post:v
	       	 POST-ACCUM DELETE (v);

	# Possible, but not recommended as the DML-sub DELETE statement occurs
	# once for each edge of the vertex v
	accumDeletedPosts = SELECT v FROM start -(posted>:e)- post:v
	       	 ACCUM DELETE (v);
}

# Need a separate query to display the results, because deletions don't take effect during the query.
CREATE QUERY selectUserPosts(vertex<person> seed) FOR GRAPH socialNet {
    start = {seed};

    userPosts = SELECT v FROM start -(posted>:e)- post:v;
    PRINT userPosts;
}

RUN QUERY selectUserPosts("person3")
RUN QUERY deletePosts("person3")
RUN QUERY selectUserPosts("person3")

# Before the deletion
{
  "error": false,
  "message": "",
  "version": {
    "edition": "developer",
    "schema": 0,
    "api": "v2"
  },
  "results": [{"userPosts": [{
    "v_id": "2",
    "attributes": {
      "postTime": "2011-02-03 01:02:42",
      "subject": "query languages"
    },
    "v_type": "post"
  }]}]
}
# Deletion; no output results requested at this point
{
  "error": false,
  "message": "",
  "version": {
    "edition": "developer",
    "schema": 0,
    "api": "v2"
  },
  "results": []
}
# After the deletion
{
  "error": false,
  "message": "",
  "version": {
    "edition": "developer",
    "schema": 0,
    "api": "v2"
  },
  "results": [{"userPosts": []}]
}

insertStmt := insertVertexStmt | insertEdgeStmt
insertVertexStmt := INSERT INTO (vertexType | name)
                 ["(" PRIMARY_ID ["," attrName]* ")"]
                 VALUES "(" ( "_" | expr ) ["," ("_" | expr)]*] ")"

insertEdgeStmt   := INSERT INTO (edgeType | EDGE name)
                 ["(" FROM "," TO ["," attrName]* ")"]
                 VALUES "(" ( "_" | expr ) [vertexType]
                 ["," ( "_" | expr ) [vertexType] ["," ("_" | expr)]*] ")"

updateStmt := UPDATE alias FROM pattern SET dmlSubStmtList [whereClause]
pattern := (vertexPattern | edgePattern)

# Change all "person" vertices with location equal to "us" to "USA"
CREATE QUERY updateEx() FOR GRAPH workNet  {
  S = {person.*};

  UPDATE s FROM S:s
  SET s.locationId = "USA",  # simple base type attribute
      s.skillList = [1,2,3]  # collection-type attribute
  WHERE s.locationId == "us";

  # The update cannot become effective within this query, so PRINT S still show "us".
  PRINT S;
}

# The second example is equivalent to the above updateEx
CREATE QUERY updateEx2() FOR GRAPH workNet  {
  S = {person.*};

  X = SELECT s
      FROM S:s
      WHERE S.locationId == "USA"
      POST-ACCUM S.locationId = "us",
                 S.skillList = [3,2,1];
  PRINT S;
}

CREATE QUERY updateEx3() FOR GRAPH workNet{
  S = {person.*};

  # update edge and target vertices' attribute
  UPDATE e FROM S:s - (worksFor:e) - :t
  SET e.startYear = e.startYear + 1, // Incremental change
      e.fullTime = false
  WHERE s.locationId == "us";

  PRINT S;
}

# change the given person's new location
CREATE QUERY updateByAssignment(VERTEX<person> v, STRING newLocation) FOR GRAPH workNet{
  v.locationId = newLocation;
}