Miscellaneous Functions
This page lists the functions in the GSQL query language that are not tied to any single data type.
coalesce()
Description
Returns the first expression that isn’t NULL
.
This function requires all its arguments have the same data type (BOOL
, INT
, FLOAT,
DOUBLE
, STRING
, or VERTEX
). The only exception is that different numeric types can be used together. In this case, all values are converted into the first argument type.
Parameters
The function takes a number of parameters and returns the first one that does not evaluate to NULL
Example
CREATE QUERY coalesceFuncEx (INT p1, DOUBLE p2) FOR GRAPH social {
PRINT COALESCE(p1, p2, 999.5); # p2 and the last value will be converted into first argument type, which is INT.
}
GSQL > RUN QUERY coalesceFuncEx(_,_)
{
"error": false,
"message": "",
"version": {
"schema": 1,
"edition": "enterprise",
"api": "v2"
},
"results": [{"coalesce(p1,p2,999.5)": 999}]
}
GSQL > RUN QUERY coalesceFuncEx(1,2)
{
"error": false,
"message": "",
"version": {
"schema": 1,
"edition": "enterprise",
"api": "v2"
},
"results": [{"coalesce(p1,p2,999.5)": 1}]
}
evaluate()
Description
Takes a string argument and interprets it as an expression which is evaluated during run-time. This enables users to create a general purpose query instead of separate queries for each specific computation.
This function cannot be nested.
The following situations generate a run-time error:
-
The expression string expressionStr cannot be compiled (unless the error is due to a non-existent vertex or edge attribute).
-
The result type of the expression does not match the parameter typeStr.
Silent failure conditions If any of the following conditions occur, the query may continue running, but the entire clause or statement in which the evaluate() function resides will fail, without producing a run-time error message. For conditional clauses (WHERE, HAVING), a failing evaluate() clause is treated as if the condition is false. An assignment statement with a failing evaluate() will not execute, and an ORDER BY clause with a failing evaluate() will not sort.
|
Parameters
Parameter | Description | Data type |
---|---|---|
|
The expression to evaluate typed as a string.
|
|
|
The return type for the function call. It must be a string
literal for a primitive data type, e.g., one of The default value is |
|
Example
CREATE QUERY evaluateEx (STRING whereCond = "TRUE", STRING postAccumIntExpr = "1") FOR GRAPH socialNet {
SetAccum<INT> @@timeSet;
MaxAccum<INT> @latestLikeTime, @latestLikePostTime;
S = {person.*};
S2 = SELECT s
FROM S:s - (liked>:e) - post:t
WHERE evaluate(whereCond)
ACCUM s.@latestLikeTime += datetime_to_epoch( e.actionTime ),
s.@latestLikePostTime += datetime_to_epoch( t.postTime )
POST-ACCUM @@timeSet += evaluate(postAccumIntExpr, "int")
;
PRINT @@timeSet;
}
GSQL > RUN QUERY evaluateEx("s.gender==\"Male\"", "s.@latestLikePostTime")
{
"error": false,
"message": "",
"results": [
{
"@@timeSet": [1263295325,1296752752,1297054971,1296788551]
}
]
}
GSQL > RUN QUERY evaluateEx("s.gender==\"Female\"", "s.@latestLikeTime + 1")
{
"error": false,
"message": "",
"results": [
{
"@@timeSet": [1263293536,1263352566,1263330726]
}
]
}