Exception Statements

declExceptStmt := EXCEPTION exceptVarName "(" errorCode ")"
exceptVarName := name
errorCode     := integer

raiseStmt := RAISE exceptVarName [errorMsg]
errorMsg := "(" expr ")"

CREATE QUERY excp_count_activity(SET<VERTEX<Person>> v_set, STRING e_type) FOR GRAPH Social_Net {
    /* Count how many edges there are from each member of the input person set to posts, along the specified edge type. */

    MapAccum<STRING,INT> @@all_count;
    EXCEPTION empty_list (40001);
    EXCEPTION no_edges   (40002);

    IF ISEMPTY(v_set) THEN
        RAISE empty_list ("Error: Input parameter 'v_set' (type SET<VERTEX<Person>>) is empty");
    END;

    Start = v_set;
    Results = SELECT s
        FROM Start:s -(:e)- post:t
        WHERE e.type == e_type
        ACCUM @@all_count += (t.subject -> 1);

    IF Results.size() == 0 THEN
        RAISE no_edges ("Error: No '" + eType + "' edges from the vertex set");
    END;
    PRINT @@all_count;
}

// Valid input: no exceptions
$ curl -X GET "http://localhost:9000/query/socialNet/excpCountActivity?v_set=person2&vSet=person6&eType=posted"
{
  "error": false,
  "message": "",
  "version": {
    "edition": "developer",
    "schema": 0,
    "api": "v2"
  },
  "results": [{
    "@@allCount": {
      "cats": 1,
      "tigergraph": 2
    }
  }]
}

// empty input set (due to spelling error in parameter name)
$ curl -X GET "http://localhost:9000/query/socialNet/excpCountActivity?vset=person2&vset=person6&eType=posted"
{
  "code": "40001",
  "error": true,
  "version": {
    "edition": "developer",
    "schema": 0,
    "api": "v2"
  },
  "message": "Error: Input parameter 'vSet' (type SET<VERTEX<person>>) is empty"
}


// no edges (due to unknown edge type)
$ curl -X GET "http://localhost:9000/query/socialNet/excpCountActivity?vSet=person2&vSet=person6&eType=commented"
{
  "code": "40002",
  "error": true,
  "version": {
    "edition": "developer",
    "schema": 0,
    "api": "v2"
  },
  "message": "Error: No 'commented' edges from the vertex set"
}

tryStmt         := TRY queryBodyStmts EXCEPTION caseExceptBlock [elseExceptBlock] END ";"
caseExceptBlock := WHEN exceptVarName THEN queryBodyStmts+
elseExceptBlock := ELSE queryBodyStmts

CREATE QUERY comp_path_valid (VERTEX<Computer> src, VERTEX<Computer> tgt, BOOL en_excp) FOR GRAPH Computer_Net {
/* Find valid paths in a computer network from a source to a target.
 Stop search once you have found some paths.
 3 Exceptions: (1) Negative connection speed, (2) Slow connection speed, (3) No path.
Set en_excp=true to raise exceptions. en_excp=false will find paths, good or bad. */

	OrAccum @@reached, @visited;
	ListAccum<STRING> @paths;
	DOUBLE min_speed = 0.4;
	INT err;

	EXCEPTION neg_speed (40001);
	EXCEPTION slow_speed (40002);
	EXCEPTION not_reached (40003);

	TRY
		Start = {src};
		// Initialize: path to src is itself.
		Start = SELECT s
			FROM Start:s
			ACCUM s.@paths = s.id;

		WHILE Start.size() != 0 AND NOT @@reached DO
			Start = SELECT t
				FROM Start:s -(:e)- :t
				WHERE t.@visited == false
				ACCUM CASE
					WHEN e.connection_speed < 0 THEN err = 1
					WHEN e.connection_speed < min_speed THEN err = 2
					WHEN t == tgt THEN @@reached += true
        END,
        // List1 * List2 -> List(each elem of List1 concat w/each elem of List2)
					t.@paths += (s.@paths * ["~"]) * [t.id]
				POST-ACCUM t.@visited = true;
        IF err == 1 AND en_excp THEN
				RAISE neg_speed ("Negative Speed");
        ELSE IF err == 2 AND en_excp THEN
				RAISE slow_speed ("Slow Speed");
			END;
		END;

		IF NOT @@reached AND en_excp THEN
			RAISE not_reached ("No path to target");
		ELSE
			result = {tgt};
			PRINT result[result.@paths];
		END;
	EXCEPTION
		WHEN neg_speed THEN PRINT "bad path: negative speed";
		WHEN slow_speed THEN PRINT "bad path: slow speed";
		WHEN not_reached THEN PRINT "no path from source to target";
	END;
}

GSQL > RUN QUERY compPathValid("c10","c12",true)
{
  "error": false,
  "message": "",
  "version": {
    "edition": "developer",
    "schema": 0,
    "api": "v2"
  },
  "results": [{"Result": [{
    "v_id": "c12",
    "attributes": {"Result.@paths": ["c10~c11~c12"]},
    "v_type": "computer"
  }]}]
}
GSQL > RUN QUERY compPathValid("c1","c12",true)
{
  "error": false,
  "message": "",
  "version": {
    "edition": "developer",
    "schema": 0,
    "api": "v2"
  },
  "results": [{"bad path: negative speed": "bad path: negative speed"}]
}
GSQL > RUN QUERY compPathValid("c10","c13",true)
{
  "error": false,
  "message": "",
  "version": {
    "edition": "developer",
    "schema": 0,
    "api": "v2"
  },
  "results": [{"bad path: slow speed": "bad path: slow speed"}]
}
GSQL > RUN QUERY compPathValid("c24","c25",true)
{
  "error": false,
  "message": "",
  "version": {
    "edition": "developer",
    "schema": 0,
    "api": "v2"
  },
  "results": [{"no path from source to target": "no path from source to target"}]
}
GSQL > RUN QUERY compPathValid("c24","c25",false)
{
  "error": false,
  "message": "",
  "version": {
    "edition": "developer",
    "schema": 0,
    "api": "v2"
  },
  "results": [{"Result": [{
    "v_id": "c25",
    "attributes": {"Result.@paths": []},
    "v_type": "computer"
  }]}]
}