Operators and Expressions

An expression is a combination of fixed values, variables, operators, function calls, and groupings that specify a computation, resulting in a data value. This section of the specification describes the literals (fixed values), operators, and functions available in the GSQL query language. It covers the subset of the EBNF definitions shown below.

However, more so than in other sections of the specification, syntax alone is not an adequate description. The semantics (functionality) of the particular operators and functions are an essential complement to the syntax.

EBNF for Operations, Functions, and Expressions
constant := numeric | stringLiteral | TRUE | FALSE | GSQL_UINT_MAX
          | GSQL_INT_MAX | GSQL_INT_MIN | TO_DATETIME "(" stringLiteral ")"

mathOperator := "*" | "/" | "%" | "+" | "-" | "<<" | ">>" | "&" | "|"

condition := expr
           | expr comparisonOperator expr
           | expr [ NOT ] IN setBagExpr
           | expr IS [ NOT ] NULL
            | expr BETWEEN expr AND expr
           | "(" condition ")"
           | NOT condition
           | condition (AND | OR) condition
           | (TRUE | FALSE)
           | expr [NOT] LIKE expr [ESCAPE escape_char]

comparisonOperator := "<" | "<=" | ">" | ">=" | "==" | "!="

aggregator := COUNT | MAX | MIN | AVG | SUM

expr := name
    | globalAccumName
		| name ".type"
		| name "." name
		| name "." localAccumName ["\'"]
		| name "." name "." name "(" [argList] ")"
        | name "." name "(" [argList] ")" [ "." FILTER "(" condition ")" ]
		| name ["<" type ["," type]* ">"] "(" argList] ")"
		| name "." localAccumName ("." name "(" [argList] ")")+ ["." name]
		| globalAccumName ("."name "(" [argList] ")")+ ["."name]
		| COALESCE "(" [argList] ")"
		| aggregator "(" [DISTINCT] setBagExpr ")"
		| ISEMPTY "(" setBagExpr ")"
		| expr mathOperator expr
		| "-" expr
		| "(" expr ")"
		| "(" argList "->" argList ")"	// key value pair for MapAccum
		| "[" argList "]"               // a list
		| constant
		| setBagExpr
		| name "(" argList ")"          // function call or a tuple object

setBagExpr := name
        | globalAccumName
    	  | name "." name
		    | name "." localAccumName
		    | name "." localAccumName ("." name "(" [argList] ")")+
		    | name "." name "(" [argList] ")" [ "." FILTER "(" condition ")" ]
		    | globalAccumName ("." name "(" [argList] ")")+
		    | setBagExpr (UNION | INTERSECT | MINUS) setBagExpr
		    | "(" argList ")"
		    | "(" setBagExpr ")"


argList := expr ["," expr]*

Constants

constant := numeric | stringLiteral | TRUE | FALSE | GSQL_UINT_MAX
          | GSQL_INT_MAX | GSQL_INT_MIN | TO_DATETIME "(" stringLiteral ")"

Each primitive data type supports constant values:

Data Type Constant Examples

Numeric types (INT, UINT, FLOAT, DOUBLE)

numeric

123 -5 45.67 2.0e-0.5

UINT

GSQL_UINT_MAX

INT

GSQL_INT_MAX GSQL_INT_MIN

boolean

TRUE FALSE

string

stringLiteral

"atoz@com" "0.25"

GSQL_UINT_MAX = 2 ^ 64 - 1 = 18446744073709551615

GSQL_INT_MAX = 2 ^ 63 - 1 = 9223372036854775807

GSQL_INT_MIN = -2 ^ 63 = -9223372036854775808

Operators

An operator is a keyword token that performs a specific computational function to return a resulting value, using the adjacent expressions (its operands) as input values. Both operators and functions compute a result from one or more inputs, but syntactically they are different. The most familiar operators are the mathematical operators for addition + and subtraction - .

The operators listed in this section are designed to behave like the operators in MySQL.

Mathematical Operators and Expressions

We support the following standard mathematical operators and meanings. The latter four (<< >> & |) are for bitwise operations. See the [bit-operators] section below.

mathOperator := "*" | "/" | "%" | "+" | "-" | "<<" | ">>" | "&" | "|"

Operator precedence

Operator precedences are shown in the following list, from the highest precedence to the lowest. Operators that are shown together on a line have the same precedence:

Operator Precedence, highest to lowest
*, /, %
-, +
<<, >>
&
|
==, >=, >, <=, <, !=

Example

  • Query

  • Results

Example 1. Math Operators + - * /
CREATE QUERY math_operators() FOR GRAPH Minimal_Net {
    INT x,y;
    INT z1,z2,z3,z4,z5;
    FLOAT f1,f2,f3,f4;

    x = 7;
    y = 3;

    z1 = x * y;    // z = 21
    z2 = x - y;    // z = 4
    z3 = x + y;    // z = 10
    z4 = x / y;    // z = 2
    z5 = x / 4.0;  // z = 1
    f1 = x / y;    // v = 2
    f2 = x / 4.0;  // v = 1.75
    f3 = x % 3;    // v = 1
    f4 = x % y;    // z = 1

    PRINT x,y;
    PRINT z1 AS x_times_y, z2 AS x_minus_y, z3 AS x_plus_y, z4 AS x_div_y, z5 AS x_div_4f;
    PRINT f1 AS x_div_y,   f2 AS x_div_4f,  f3 AS x_mod_3,  f4 AS x_mod_y;
}
mathOperators.json Results
GSQL > RUN QUERY math_operators()
{
  "error": false,
  "message": "",
  "version": {
    "schema": 0,
    "edition": "enterprise",
    "api": "v2"
  },
  "results": [
    {
      "x": 7,
      "y": 3
    },
    {
      "x_div_4f": 1,
      "x_times_y": 21,
      "x_div_y": 2,
      "x_minus_y": 4,
      "x_plus_y": 10
    },
    {
      "x_mod_3": 1,
      "x_div_4f": 1.75,
      "x_mod_y": 1,
      "x_div_y": 2
    }
  ]
}

Automatic numeric type casting

When the two operands for a mathematical operator have different data types, the operator will first make an internal copy of the operand with the "lower" precision and convert it the "higher" precision, according to this hierarchy, from lowest to highest:

INT → UINT → FLOAT → DOUBLE

The final result value will have this higher precision.

Example 1: 

INT A = 7;
INT B = 2;
PRINT A / B;

Both A and B are INT, so integer division is performed. The output is 3.

Example 2:

FLOAT C = 7;
INT D = 2.0;
PRINT C / D;

C will be copied to an internal FLOAT type variable, so that the division operation is 7.0/2.0 = 3.5;

Example 3:

INT E = -7;
UINT F = 2;
PRINT E  / F;

E will be copied to an internal UINT type variable which cannot properly handle its negative value. The result will be wrong,

Operations using UINT and INT will be converted to UINT-only operations, destroying any negative values.

If your INT values or resulting values could be negative, and all of your values will be within the range of INT, then consider explicitly converting your UINT values to INT, so that the operators work exclusively with INT.

Boolean Operators

We support the standard Boolean operators and standard order of precedence: AND, OR, NOT

Bit Operators

Bit operators (<< >> & |) operate on integers and return an integer.

TigerGraph implements bit operators in the same way that C++ does. This returns an undefined result in the following situations:

  • If you left-shift a signed number so that the sign bit is affected

  • If the additive expression is negative

  • If the additive expression is greater than or equal to the number of bits in the (promoted) shift expression

Bit Operators
CREATE QUERY bit_operation_test() FOR GRAPH Minimal_Net{
    PRINT 80 >> 2;     // 20
    PRINT 80 << 2;     // 320
    PRINT 2 + 80 >> 4; // 5
    PRINT 2 | 3 ;      // 3
    PRINT 2 & 3 ;      // 2
    PRINT 2 | 3 + 2;   // 7
    PRINT 2 & 3 - 2;   // 0
}

String Operators

The + operator can be used for concatenating strings.

CREATE QUERY concat_test() FOR GRAPH Minimal_Net{
    STRING first_string, second_string, third_string;
    first_string = "first string";
    second_string = "second string";
    third_string = first_string + " " + second_string;
    PRINT third_string;   // "first string second string"
}

Tuple Fields

The fields of the tuple can be accessed using the dot operator.

Comparison Operators and Conditions

A condition is an expression that evaluates to a boolean value of either true or false. One type of condition uses the familiar comparison operators. A comparison operator compares two numeric or string values.

comparisonOperator := "<" | "<=" | ">" | ">=" | "==" | "!="

condition := expr
           | expr comparisonOperator expr
           | expr [ NOT ] IN setBagExpr
           | expr IS [ NOT ] NULL
           | expr BETWEEN expr AND expr
           | "(" condition ")"
           | NOT condition
           | condition (AND | OR) condition
           | (TRUE | FALSE)
           | expr [NOT] LIKE expr [ESCAPE escape_char]

Strings are compared based on standard lexicographical ordering:
(space) < (digit) < (uppercase_letter) < (lowercase_letter).

BETWEEN …​ AND …​

The expression expr1 BETWEEN expr2 AND expr3 is true if the value expr1 is in the range from expr2 to expr3, including the endpoint values. Each expression must be numeric.

expr1 BETWEEN expr2 AND expr3 is equivalent to expr1 ⇐ expr3 AND expr1 >= expr2.

BETWEEN AND example
CREATE QUERY math_operator_between() FOR GRAPH Minimal_Net {
    INT x;
    BOOL b;
    x = 1;
    b = (x BETWEEN 0 AND 100); PRINT b;  // True
    b = (x BETWEEN 1 AND 2); PRINT b;    // True
    b = (x BETWEEN 0 AND 1); PRINT b;    // True
}

IS NULL, IS NOT NULL

IS NULL and IS NOT NULL can be used for checking whether an optional parameter is given any value.

Example

  • Query

  • Results

IS NULL example
CREATE QUERY parameter_is_null (INT p) FOR GRAPH Minimal_Net {
    IF p IS NULL THEN
        PRINT "p is null";
    ELSE
        PRINT "p is not null";
    END;
}
parameterIsNULL.json Results
GSQL > RUN QUERY parameter_is_null(_)
{
  "error": false,
  "message": "",
  "version": {
    "schema": 0,
    "edition": "enterprise",
    "api": "v2"
  },
  "results": [{"\"p is null\"": "p is null"}]
}

GSQL > RUN QUERY parameter_is_null(3)
{
  "error": false,
  "message": "",
  "version": {
    "schema": 0,
    "edition": "enterprise",
    "api": "v2"
  },
  "results": [{"\"p is not null\"": "p is not null"}]
}

Every attribute value stored in GSQL is a valid value, so IS NULL and IS NOT NULL are only effective for query parameters.

LIKE

expr [NOT] LIKE expr [ESCAPE escape_char]

The LIKE operator is used for string pattern matching and can only be used in WHERE clauses. The expression string1 LIKE string_pattern evaluates to boolean true if string1 matches the pattern in string_pattern; otherwise, it is false.

Both operands must be strings. Additionally, while string1 can be a function call (e.g. lower(string_variable), string_pattern must be a string literal or a parameter. string_pattern cannot be the result of concatenating other strings, nor can it be a function call.

A string_pattern can contain characters as well as the following wildcard and other special symbols, in order to express a pattern (<char_list> indicates a placeholder):

Character or syntax Description Example

%

Matches zero or more characters.

%abc% matches any string which contains the sequence "abc".

_(underscore)

Matches any single character.

_abc_ematches any 6-character string where the 2nd to 4th characters are "abc" and the last character is "e".

[<char_list>]

Matches any character in a char list. A char list is a concatenated character set, with no separators.

[Tiger]matches either T, i, g, e, or r.

[^<char_list>]

Matches any character NOT in a char list.

[^qxz]matches any character other than q, x, or z.

[!<char_list>]

Matches any character NOT in a char list.

α-β

(Special syntax within a char list) matches a character in the range from α to β. A char list can have multiple ranges.

[a-mA-M0-3]matches a letter from a to m, upper or lower case, or a digit from 0 to 3.

\\

(Special syntax within a char list) matches the character \

\\]

(Special syntax within a char list) matches the character ] No special treatment is needed for [ inside a char list.

%[\\]!]matches any string which ends with either ] or !
Matching backslashes

When you load a string that contains a backslash into TigerGraph, the backslash itself is escaped with another backslash. In a string pattern, two backslashes match one backslash in an input string. This applies to both backslashes - the one used to escape the other and the one being escaped.

For example, if the string \abc is loaded into Vertex.attribute. Then:

  • The actual value of Vertex.attribute in the graph is "\\abc". The size of the string is 4, because the first backslash is used to escape the second backslash and doesn’t count towards the size of the string.

  • Vertex.attribute == "\\abc" returns true, because a backslash is required to escape the other backslash.

  • Vertex.attribute LIKE "\\\\abc" returns true, because it takes two backslashes in a string pattern to match one backslash in a string.

ESCAPE escape_char

The optional ESCAPE escape_char clause is used to define an escape character. When escape_char occurs in string_pattern, then the next character is interpreted literally, instead of as a pattern matching operator. For example, if we want to specify the pattern "any string ending with the '%' character", we could use
"%\%" ESCAPE "\"

The first "%" has its usual pattern-matching meaning "zero or more characters".
"\%" means a literal percentage character, because it starts with the escape character "\".

Example

  • Query Without Parameters

  • Query With Parameters

  • Results

Example query using LIKE operator
CREATE QUERY print_a_posts() FOR GRAPH Social_Net {
    posts = {Post.*};
    a_posts = SELECT v FROM posts:v
        // Returns all posts with the character "a" in the subject
        WHERE v.subject LIKE "%a%";
	PRINT a_posts;
}
Example parameterized query
CREATE QUERY print_posts(STRING search_string) FOR GRAPH Social_Net {
    STRING search_param;
    search_param = "%" + search_string + "%";
    posts = {Post.*};
    a_posts = SELECT v FROM posts:v
        // Returns all posts with the search_string in the subject
        WHERE v.subject LIKE search_param;
    PRINT a_posts;
}
{
  "error": false,
  "message": "",
  "version": {
    "schema": 0,
    "edition": "enterprise",
    "api": "v2"
  },
  "results": [{"aPosts": [
    {
      "v_id": "2",
      "attributes": {
        "postTime": "2011-02-03 01:02:42",
        "subject": "query languages"
      },
      "v_type": "post"
    },
    {
      "v_id": "8",
      "attributes": {
        "postTime": "2011-02-03 17:05:52",
        "subject": "cats"
      },
      "v_type": "post"
    },
    {
      "v_id": "0",
      "attributes": {
        "postTime": "2010-01-12 11:22:05",
        "subject": "Graphs"
      },
      "v_type": "post"
    },
    {
      "v_id": "1",
      "attributes": {
        "postTime": "2011-03-03 23:02:00",
        "subject": "tigergraph"
      },
      "v_type": "post"
    }
  ]}]
}

Vertex, edge, and accumulator attributes

Accessing attributes

Attributes on vertices or edges are defined in the graph schema. Additionally, each vertex and edge has a built-in STRING attribute called type which represents the user-defined type of that edge or vertex. These attributes, including type, can be accessed for a particular edge or vertex with the dot operator:

Accessing attributes with a known name.
name ".type"   // read only. Returns vertexType or edgeType of name
name "." attrName // read/write. Accesses attribute called attrName
Dynamic query support

The name of the attribute can be parameterized using the getAttr and setAttr vertex functions, described later in this section. This allows you to write dynamic query procedures where the attribute names are specified when you run the query.

For example, the following code snippet shows two different SELECT statements which produce equivalent results. The first uses the dot operator on the vertex variable v to access the subject attribute, which is defined in the graph schema. The FROM clause in the first SELECT statement necessitates that any target vertices will be of type Post (also defined in the graph schema). The second SELECT schema checks that the vertex variable v's type is a Post vertex by using the dot operator to access the built-in type attribute.

Example

  • Query

  • Results

Accessing vertex variable attributes
CREATE QUERY coffee_related_posts() FOR GRAPH Social_Net {
    all_vertices = {ANY};
    results = SELECT v FROM all_vertices:s -(:e)- Post:v
        WHERE v.subject == "coffee";
    PRINT results;
    results = SELECT v FROM all_vertices:s -(:e)- :v
        WHERE v.type == "Post" AND v.subject == "coffee";
    PRINT results;
}
Results for Query coffeeRelatedPosts
{
  "error": false,
  "message": "",
  "version": {
    "schema": 0,
    "edition": "enterprise",
    "api": "v2"
  },
  "results": [
    {"results": [{
      "v_id": "4",
      "attributes": {
        "subject": "coffee",
        "post_time": "2011-02-07 05:02:51"
      },
      "v_type": "Post"
    }]},
    {"results": [{
      "v_id": "4",
      "attributes": {
        "subject": "coffee",
        "post_time": "2011-02-07 05:02:51"
      },
      "v_type": "Post"
    }]}
  ]
}

Accumulator Functions

This section describes functions that apply to all or most accumulators. Other accumulator functions for each accumulator type are illustrated in the "Accumulator Type" section.

Previous value of accumulator

The tick operator ' can be used to read the value of an accumulator as it was at the start an ACCUM clause, before any changes that took place within the ACCUM clause. It can only be used in the POST-ACCUM clause. A typical use is to compare the value of the accumulator before and after the ACCUM clause. The PageRank algorithm provides a good example:

v = SELECT s
    FROM start:s - (e_type:e) -> :t
    ACCUM t.@received_score += s.@score/(s.outdegree(e_type))
    POST-ACCUM
        s.@score = (1.0 - damping) + damping * s.@received_score,
        s.@received_score = 0,
        @@max_diff += abs(s.@score - s.@score');

In the last line, we compute @@max_diff as the absolute value of the difference between the post-ACCUM score (s.@score) and the pre-ACCUM score (s.@score').

Set/Bag Expression and Operators

SELECT blocks take an input vertex set and perform various selection and filtering operations to produce an output set. Therefore, set/bag expressions and their operators are a useful and powerful part of the GSQL query language. A set/bag expression can use either SetAccum or BagAccum.

EBNF
setBagExpr := name
        | globalAccumName
    	  | name "." name
		    | name "." localAccumName
		    | name "." localAccumName ("." name "(" [argList] ")")+
		    | name "." name "(" [argList] ")" [ "." FILTER "(" condition ")" ]
		    | globalAccumName ("." name "(" [argList] ")")+
		    | setBagExpr (UNION | INTERSECT | MINUS) setBagExpr
		    | "(" argList ")"
		    | "(" setBagExpr ")"

Set/Bag expression operators - UNION, INTERSECT, MINUS

The operators are straightforward, when two operands are both sets, the result expression is a set. When at least one operand is a bag, the result expression is a bag. If one operand is a bag and the other is a set, the operator treats the set operand as a bag containing one of each value.

Set/bag operator examples

  • Query

  • Results

Set/Bag Operator Examples
CREATE QUERY set_operators_ex() FOR GRAPH Minimal_Net   {
    SetAccum<INT> @@set_a, @@set_b, @@a_union_b, @@a_intsct_b, @@a_minus_b;
    BagAccum<INT> @@bag_d, @@bag_e, @@d_union_e, @@d_intsct_e, @@d_minus_e;
    BagAccum<INT> @@d_minus_a, @@d_union_a, @@a_union_b_bag;

    BOOL x;

    @@set_a = (1,2,3,4);      PRINT @@set_a;
    @@set_b = (2,4,6,8);      PRINT @@set_b;

    @@a_union_b = @@set_a UNION @@set_b ;      PRINT @@a_union_b;   // (1, 2, 3, 4, 6, 8)
    @@a_intsct_b = @@set_a INTERSECT @@set_b;  PRINT @@a_intsct_b;   // (2, 4)
    @@a_minus_b = @@set_a MINUS @@set_b ;      PRINT @@a_minus_b;   // C = (1, 3)

    @@bag_d = (1,2,2,3);      PRINT @@bag_d;
    @@bag_e = (2,3,5,7);      PRINT @@bag_e;

    @@d_union_e = @@bag_d UNION @@bag_e;     PRINT @@d_union_e;   // (1, 2, 2, 2, 3, 3, 5, 7)
    @@d_intsct_e = @@bag_d INTERSECT @@bag_e; PRINT @@d_intsct_e; // (2, 3)
    @@d_minus_e = @@bag_d MINUS @@bag_e;     PRINT @@d_minus_e;   // (1, 2)
    @@d_minus_a = @@bag_d MINUS @@set_a;     PRINT @@d_minus_a;   // (2)
    //  bag UNION set is a bag
    @@d_union_a = @@bag_d UNION @@set_a;     PRINT @@d_union_a;   // (1, 1, 2, 2, 2, 3, 3, 4)
    // because set UNION set is a set
    @@a_union_b_bag = @@set_a UNION @@set_b;  PRINT @@a_union_b_bag;  // (1, 2, 3, 4, 6, 8)
}
CREATE QUERY set_operators_ex() FOR GRAPH Minimal_Net   {
    SetAccum<INT> @@set_a, @@set_b, @@a_union_b, @@a_intsct_b, @@a_minus_b;
    BagAccum<INT> @@bag_d, @@bag_e, @@d_union_e, @@d_intsct_e, @@d_minus_e;
    BagAccum<INT> @@d_minus_a, @@d_union_a, @@a_union_b_bag;

    BOOL x;

    @@set_a = (1,2,3,4);      PRINT @@set_a;
    @@set_b = (2,4,6,8);      PRINT @@set_b;

    @@a_union_b = @@set_a UNION @@set_b ;      PRINT @@a_union_b;   // (1, 2, 3, 4, 6, 8)
    @@a_intsct_b = @@set_a INTERSECT @@set_b;  PRINT @@a_intsct_b;   // (2, 4)
    @@a_minus_b = @@set_a MINUS @@set_b ;      PRINT @@a_minus_b;   // C = (1, 3)

    @@bag_d = (1,2,2,3);      PRINT @@bag_d;
    @@bag_e = (2,3,5,7);      PRINT @@bag_e;

    @@d_union_e = @@bag_d UNION @@bag_e;     PRINT @@d_union_e;   // (1, 2, 2, 2, 3, 3, 5, 7)
    @@d_intsct_e = @@bag_d INTERSECT @@bag_e; PRINT @@d_intsct_e; // (2, 3)
    @@d_minus_e = @@bag_d MINUS @@bag_e;     PRINT @@d_minus_e;   // (1, 2)
    @@d_minus_a = @@bag_d MINUS @@set_a;     PRINT @@d_minus_a;   // (2)
    //  bag UNION set is a bag
    @@d_union_a = @@bag_d UNION @@set_a;     PRINT @@d_union_a;   // (1, 1, 2, 2, 2, 3, 3, 4)
    // because set UNION set is a set
    @@a_union_b_bag = @@set_a UNION @@set_b;  PRINT @@a_union_b_bag;  // (1, 2, 3, 4, 6, 8)
}

The result of these operators is another set or bag, so these operations can be nested and chained to form more complex expressions, such as

(setBagExpr_A INTERSECT (setBagExpr_B UNION setBagExpr_C) ) MINUS setBagExpr_D

Set/Bag Expression Membership Operators

For example , suppose setBagExpr_A is ("a", "b", "c")

"a" IN setBagExpr_A            => true
"d" IN setBagExpr_A            => false
"a" NOT IN setBagExpr_A        => false
"d" NOT IN setBagExpr_A        => true

The IN and NOT IN operators support all base types on the left-hand side, and any set/bag expression on the right-hand side. The base type must be the same as the accumulator’s element type. IN and NOT IN return a BOOL value.

The following example uses NOT IN to exclude neighbors that are on a blocked list.

Example

  • Query

  • Result

Set Membership example
CREATE QUERY friends_not_in_blocked_list (VERTEX<Person> seed,
    SET<VERTEX<Person>> blocked_list) FOR GRAPH Social_Net {
    start = {seed};
    result = SELECT v
        FROM start:s-(Friend:e)-Person:v
        WHERE v NOT IN blocked_list;
    PRINT result;
}
Results for Query friends_not_in_blocked_list
GSQL > RUN QUERY friends_not_in_blocked_list("person1", ["person2"])
{
  "error": false,
  "message": "",
  "version": {
    "edition": "developer",
    "schema": 0,
    "api": "v2"
  },
  "results": [{"Result": [{
    "v_id": "person8",
    "attributes": {
      "gender": "Male",
      "id": "person8"
    },
    "v_type": "Person"
  }]}]
}

Subqueries

A query defined with a RETURNS header following its CREATE statement is called a subquery. Subqueries act as callable functions in GSQL: they take parameters, perform a set of actions and return a value.

A subquery must end with a return statement to pass its output value to a query. Exactly one type is allowed in the RETURNS header, and thus the RETURN statement can only return one expression.

A subquery must be created before the query that calls the subquery. A subquery must be installed either before or in the same INSTALL QUERY command with the query that calls the subquery.

  • A distributed query cannot call another distributed query

  • A non-distributed query cannot call a distributed query in an ACCUM or POST-ACCUM clause
Main Components of a Subquery
CREATE QUERY <query_name>() FOR GRAPH <Graph_Name> (1)
RETURNS (INT) (2)
{
    // ...
    // Query body goes here
    // ...
    RETURN <return_value> (3)
}
1 Parameters are optional.
2 A subquery has a RETURNS header specifying its return type.
3 The return statement of a subquery. Return value must be the same type as specified in the RETURNS header.

Parameter types

A subquery parameter can only be one of the following types:

  • Primitives: INT, UINT, FLOAT, DOUBLE, STRING, BOOL

  • VERTEX

  • A set or bag of primitive or VERTEX elements

Return types

A subquery’s return value can be any base type variable or accumulator with the following exceptions:

  • If the return type is a HeapAccum or GroupByAccum that has a user-defined tuple as an element, the user-defined tuple must be defined at the catalog level.

  • If the return type is a BagAccum, SetAccum, or ListAccum with a tuple as its element, the tuple does not need to be defined at the catalog level and can be anonymous.

A HeapAccum with a catalog-level tuple can be returned anonymously by a subquery, just like BagAccum, SetAccum, and ListAccum.

If the capacity of the HeapAccum is declared, the returned HeapAccum will be resized according to the capacity upon returning. The subquery will not return more tuples than the declared HeapAccum capacity. This resize only happens upon returning the value and will not affect the query body.

Example

The following query uses a subquery that returns an anonymous tuple:

  • Subquery

  • Query

CREATE QUERY sub_query(VERTEX x)
RETURNS (ListAccum<TUPLE<INT, STRING, DOUBLE>>)
{
    TYPEDEF tuple<INT a, STRING b, DOUBLE c> My_Tuple;
    ListAccum<My_Tuple> @@res;
    RETURN @@res;
}
CREATE QUERY main_query() {
    TYPEDEF tuple<INT a, STRING b, DOUBLE c> My_Tuple1;
    ListAccum<My_Tuple1> @@acc1;
    V = SELECT src FROM xxxx:src
        // Put the elements returned from the subQuery at the end of the @@Acc1
        ACCUM @@Acc1 += sub_query(src);
    PRINT @@acc1;
}

Recursive subqueries

Recursion is supported for subqueries and a subquery can call itself. The following example subquery takes a set of persons as starting points, and returns all the friends within a given distance.

While recursive subqueries may look simpler in writing, they are usually not as efficient as iterative subqueries in GSQL.

Example

  • Subquery

  • Query

  • Result

CREATE QUERY sub_find_friends_in_distance(SET<VERTEX> seeds, INT distance)
FOR GRAPH Friend_Net RETURNS (SET<VERTEX>)
{
	IF distance <= 0 THEN   // Base case
        // When distance is 0, return the seed vertices themselves
        RETURN seeds;
	ELSE
        seed_vs = seeds; // Initialize starting vertices
        // Select 1-hop neighbors from the starting points
        next_vs = SELECT v FROM seed_vs -(Friend:e)- :v;
        /* Find the (distance-1)-hop neighbors of the 1-hop neighbors
          and return the union of the starting vertices and neighbors */
        RETURN seeds UNION sub_find_friends_in_distance(next_vs, distance - 1);
    END;
}
CREATE QUERY find_friends_in_distance(VERTEX<Person> p, INT distance) FOR GRAPH Friend_Net {
	seed = {p};
    //PRINT All Persons;
	PRINT sub_find_friends_in_distance(seed, distance) AS friends;
}

Test cases: Starting from person1, search to a distance of 1 and a distance of 2.

RUN QUERY find_friends_in_distance("person1", 1)
{
  "error": false,
  "message": "",
  "version": {
    "schema": 0,
    "edition": "enterprise",
    "api": "v2"
  },
  "results": [{"friends": [
    "person4",
    "person2",
    "person3",
    "person1"
  ]}]
}

RUN QUERY find_friends_in_distance("person1", 2)
{
  "error": false,
  "message": "",
  "version": {
    "schema": 0,
    "edition": "enterprise",
    "api": "v2"
  },
  "results": [{"friends": [
    "person4",
    "person2",
    "person3",
    "person6",
    "person8",
    "person9",
    "person1"
  ]}]
}

Examples of Expressions

Below is a list of examples of expressions. Note that ( argList ) is a set/bag expression, while [ argList ] is a list expression.

  • Query

  • Results

Expression Examples
CREATE QUERY expression_ex() FOR GRAPH Work_Net {
    TYPEDEF TUPLE<STRING country_name, STRING company_name> company_info;

    ListAccum<STRING> @company_names;
    SumAccum<INT> @company_count;
    SumAccum<INT> @number_of_relationships;
    ListAccum<company_info> @info;
    MapAccum< STRING,ListAccum<STRING> > @@company_employee_relationships;
    SumAccum<INT> @@total_relationship_count;

    ListAccum<INT> @@value_list;
    SetAccum<INT> @@value_set;

    SumAccum<INT> @@a;
    SumAccum<INT> @@b;

    // expr := constant
    @@a = 10;

    // expr := ["@@"] name
    @@b = @@a;

    // expr := expr mathOperator expr
    @@b = @@a + 5;

    // expr := "(" expr ")"
    @@b = (@@a + 5);

    // expr := "-" expr
    @@b = -(@@a + 5);

    PRINT @@a, @@b;

    // expr := "[" argList "]"   // a list
    @@value_list = [1,2,3,4,5];
    @@value_list += [24,80];

    // expr := "(" argList ")"  // setBagExpr
    @@value_set += (1,2,3,4,5);

    // expr := ( COUNT | ISEMPTY | MAX | MIN | AVG | SUM ) "(" setBagExpr ")"
    PRINT MAX(@@value_list);
    PRINT AVG(@@value_list);

    seed = {ANY};

    company1 = SELECT t FROM seed:s -(Works_For)- :t WHERE (s.id == "company1");
    company2 = SELECT t FROM seed:s -(Works_For)- :t WHERE (s.id == "company2");

    // expr := setBagExpr
    works_for_both = company1 INTERSECT company2;
    PRINT works_for_both;

    // expr := name "." "type"
    employees = SELECT s FROM seed:s WHERE (s.type == "Person");

    employees = SELECT s FROM employees:s -(Works_For)- :t

    ACCUM
        // expr := name "." ["@"] name
        s.@company_names += t.id,

        // expr := name "."name "(" [argList] ")" [ "."FILTER "(" condition ")" ]
        s.@number_of_relationships += s.outdegree(),

        // expr := name ["<" type ["," type"]* ">"] "(" [argList] ")"
        s.@info += company_info(t.country, t.id)

    POST-ACCUM
        // expr := name "."localAccum_name ("."name "(" [argList] ")")+ ["."name]
        s.@company_count += s.@company_names.size(),

    // expr := name "."localAccum_name ["\'"]
    @@total_relationship_count += s.@company_count,

    FOREACH comp IN s.@company_names DO
       // expr := "(" argList "->" argList ")"
       @@company_employee_relationships += (s.id -> comp)
    END;

    PRINT employees;
    PRINT @@total_relationship_count;
    PRINT @@company_employee_relationships;

    // expr := globalAccum_name ("."name "(" [argList] ")")+ ["."name]
    PRINT @@company_employee_relationships.size();
}
expressionEx.json Results
[
  {
    "@@a": 10,
    "@@b": -15
  },
  {
    "max(@@value_list)": 80
  },
  {
    "avg(@@value_list)": 17
  },
  {
    "works_for_both": [
      {
        "attributes": {
          "@company_count": 0,
          "@company_names": [],
          "@info": [],
          "@number_of_relationships": 0,
          "id": "person1",
          "interest_list": [
            "management",
            "financial"
          ],
          "interest_set": [
            "financial",
            "management"
          ],
          "location_id": "us",
          "skill_list": [
            1,
            2,
            3
          ],
          "skill_set": [
            1,
            2,
            3
          ]
        },
        "v_id": "person1",
        "v_type": "Person"
      },
      {
        "attributes": {
          "@company_count": 0,
          "@company_names": [],
          "@info": [],
          "@number_of_relationships": 0,
          "id": "person2",
          "interest_list": [
            "engineering"
          ],
          "interest_set": [
            "engineering"
          ],
          "location_id": "chn",
          "skill_list": [
            2,
            3,
            5,
            6
          ],
          "skill_set": [
            2,
            3,
            5,
            6
          ]
        },
        "v_id": "person2",
        "v_type": "Person"
      }
    ]
  },
  {
    "employees": [
      {
        "attributes": {
          "@company_count": 2,
          "@company_names": [
            "company2",
            "company3"
          ],
          "@info": [
            {
              "company_name": "company2",
              "country_name": "chn"
            },
            {
              "company_name": "company3",
              "country_name": "jp"
            }
          ],
          "@number_of_relationships": 4,
          "id": "person7",
          "interest_list": [
            "art",
            "sport"
          ],
          "interest_set": [
            "sport",
            "art"
          ],
          "location_id": "us",
          "skill_list": [
            8,
            6
          ],
          "skill_set": [
            6,
            8
          ]
        },
        "v_id": "person7",
        "v_type": "Person"
      },
      {
        "attributes": {
          "@company_count": 2,
          "@company_names": [
            "company2",
            "company1"
          ],
          "@info": [
            {
              "company_name": "company2",
              "country_name": "chn"
            },
            {
              "company_name": "company1",
              "country_name": "us"
            }
          ],
          "@number_of_relationships": 4,
          "id": "person1",
          "interest_list": [
            "management",
            "financial"
          ],
          "interest_set": [
            "financial",
            "management"
          ],
          "location_id": "us",
          "skill_list": [
            1,
            2,
            3
          ],
          "skill_set": [
            1,
            2,
            3
          ]
        },
        "v_id": "person1",
        "v_type": "Person"
      },
      {
        "attributes": {
          "@company_count": 1,
          "@company_names": [
            "company2"
          ],
          "@info": [
            {
              "company_name": "company2",
              "country_name": "chn"
            }
          ],
          "@number_of_relationships": 1,
          "id": "person5",
          "interest_list": [
            "sport",
            "financial",
            "engineering"
          ],
          "interest_set": [
            "engineering",
            "financial",
            "sport"
          ],
          "location_id": "can",
          "skill_list": [
            8,
            2,
            5
          ],
          "skill_set": [
            2,
            5,
            8
          ]
        },
        "v_id": "person5",
        "v_type": "Person"
      },
      {
        "attributes": {
          "@company_count": 2,
          "@company_names": [
            "company2",
            "company1"
          ],
          "@info": [
            {
              "company_name": "company2",
              "country_name": "chn"
            },
            {
              "company_name": "company1",
              "country_name": "us"
            }
          ],
          "@number_of_relationships": 4,
          "id": "person2",
          "interest_list": [
            "engineering"
          ],
          "interest_set": [
            "engineering"
          ],
          "location_id": "chn",
          "skill_list": [
            2,
            3,
            5,
            6
          ],
          "skill_set": [
            2,
            3,
            5,
            6
          ]
        },
        "v_id": "person2",
        "v_type": "Person"
      },
      {
        "attributes": {
          "@company_count": 1,
          "@company_names": [
            "company1"
          ],
          "@info": [
            {
              "company_name": "company1",
              "country_name": "us"
            }
          ],
          "@number_of_relationships": 1,
          "id": "person3",
          "interest_list": [
            "teaching"
          ],
          "interest_set": [
            "teaching"
          ],
          "location_id": "jp",
          "skill_list": [
            4,
            1,
            6
          ],
          "skill_set": [
            1,
            4,
            6
          ]
        },
        "v_id": "person3",
        "v_type": "Person"
      },
      {
        "attributes": {
          "@company_count": 1,
          "@company_names": [
            "company1"
          ],
          "@info": [
            {
              "company_name": "company1",
              "country_name": "us"
            }
          ],
          "@number_of_relationships": 1,
          "id": "person8",
          "interest_list": [
            "management"
          ],
          "interest_set": [
            "management"
          ],
          "location_id": "chn",
          "skill_list": [
            1,
            5,
            2
          ],
          "skill_set": [
            1,
            2,
            5
          ]
        },
        "v_id": "person8",
        "v_type": "Person"
      },
      {
        "attributes": {
          "@company_count": 2,
          "@company_names": [
            "company2",
            "company3"
          ],
          "@info": [
            {
              "company_name": "company2",
              "country_name": "chn"
            },
            {
              "company_name": "company3",
              "country_name": "jp"
            }
          ],
          "@number_of_relationships": 4,
          "id": "person9",
          "interest_list": [
            "financial",
            "teaching"
          ],
          "interest_set": [
            "teaching",
            "financial"
          ],
          "location_id": "us",
          "skill_list": [
            4,
            7,
            2
          ],
          "skill_set": [
            2,
            4,
            7
          ]
        },
        "v_id": "person9",
        "v_type": "Person"
      },
      {
        "attributes": {
          "@company_count": 1,
          "@company_names": [
            "company2"
          ],
          "@info": [
            {
              "company_name": "company2",
              "country_name": "chn"
            }
          ],
          "@number_of_relationships": 1,
          "id": "person4",
          "interest_list": [
            "football"
          ],
          "interest_set": [
            "football"
          ],
          "location_id": "us",
          "skill_list": [
            4,
            1,
            10
          ],
          "skill_set": [
            1,
            4,
            10
          ]
        },
        "v_id": "person4",
        "v_type": "Person"
      },
      {
        "attributes": {
          "@company_count": 2,
          "@company_names": [
            "company3",
            "company1"
          ],
          "@info": [
            {
              "company_name": "company3",
              "country_name": "jp"
            },
            {
              "company_name": "company1",
              "country_name": "us"
            }
          ],
          "@number_of_relationships": 4,
          "id": "person10",
          "interest_list": [
            "football",
            "sport"
          ],
          "interest_set": [
            "sport",
            "football"
          ],
          "location_id": "us",
          "skill_list": [
            3
          ],
          "skill_set": [
            3
          ]
        },
        "v_id": "person10",
        "v_type": "Person"
      },
      {
        "attributes": {
          "@company_count": 1,
          "@company_names": [
            "company1"
          ],
          "@info": [
            {
              "company_name": "company1",
              "country_name": "us"
            }
          ],
          "@number_of_relationships": 1,
          "id": "person6",
          "interest_list": [
            "music",
            "art"
          ],
          "interest_set": [
            "art",
            "music"
          ],
          "location_id": "jp",
          "skill_list": [
            7,
            10
          ],
          "skill_set": [
            7,
            10
          ]
        },
        "v_id": "person6",
        "v_type": "Person"
      },
      {
        "attributes": {
          "@company_count": 1,
          "@company_names": [
            "company4"
          ],
          "@info": [
            {
              "company_name": "company4",
              "country_name": "us"
            }
          ],
          "@number_of_relationships": 1,
          "id": "person12",
          "interest_list": [
            "music",
            "engineering",
            "teaching",
            "teaching",
            "teaching"
          ],
          "interest_set": [
            "teaching",
            "engineering",
            "music"
          ],
          "location_id": "jp",
          "skill_list": [
            1,
            5,
            2,
            2,
            2
          ],
          "skill_set": [
            1,
            2,
            5
          ]
        },
        "v_id": "person12",
        "v_type": "Person"
      },
      {
        "attributes": {
          "@company_count": 1,
          "@company_names": [
            "company5"
          ],
          "@info": [
            {
              "company_name": "company5",
              "country_name": "can"
            }
          ],
          "@number_of_relationships": 1,
          "id": "person11",
          "interest_list": [
            "sport",
            "football"
          ],
          "interest_set": [
            "football",
            "sport"
          ],
          "location_id": "can",
          "skill_list": [
            10
          ],
          "skill_set": [
            10
          ]
        },
        "v_id": "person11",
        "v_type": "Person"
      }
    ]
  },
  {
    "@@total_relationship_count": 17
  },
  {
    "@@company_employee_relationships": {
      "person1": [
        "company2",
        "company1"
      ],
      "person10": [
        "company3",
        "company1"
      ],
      "person11": [
        "company5"
      ],
      "person12": [
        "company4"
      ],
      "person2": [
        "company2",
        "company1"
      ],
      "person3": [
        "company1"
      ],
      "person4": [
        "company2"
      ],
      "person5": [
        "company2"
      ],
      "person6": [
        "company1"
      ],
      "person7": [
        "company2",
        "company3"
      ],
      "person8": [
        "company1"
      ],
      "person9": [
        "company2",
        "company3"
      ]
    }
  },
  {
    "@@company_employee_relationships.size()": 12
  }
]

Examples of Expression Statements

  • Query

  • Results

Expression Statement Examples
CREATE QUERY expression_stmnt_ex() FOR GRAPH Work_Net {
    TYPEDEF TUPLE<STRING country_name, STRING company_name> Company_Info;

    ListAccum<Company_Info> @employer_info;
    SumAccum<INT> @@a;
    ListAccum<STRING> @employers;
    SumAccum<INT> @employer_count;
    SetAccum<STRING> @@country_set;

    INT x;

    // exprStmnt := name "=" expr
    x = 10;

    // gAccumAssignStmt := globalAccumName ("+=" | "=") expr
    @@a = 10;

    PRINT x, @@a;

    start = {Person.*};

    employees = SELECT s FROM start:s -(Works_For)- :t
        ACCUM // exprStmnt := name "."localAccumName ("+="| "=") expr
             s.@employers += t.id,
       		 // exprStmnt := name ["<" type ["," type"]* ">"] "(" [argList] ")"
		     s.@employer_info += Company_Info(t.country, t.id),
             // gAccumAccumStmt := globalAccumName "+=" expr
		     @@country_set += t.country
	         // exprStmnt := name "."localAccumName ["."name "(" [argList] ")"]
	         POST-ACCUM s.@employer_count += s.@employers.size();

    // exprStmnt := globalAccumName ["."name "(" [argList] ")"]+
    PRINT @@country_set.size();
    PRINT employees;
}
GSQL > RUN QUERY expression_stmnt_ex()
[
  {
    "@@a": 10,
    "x": 10
  },
  {
    "@@country_set.size()": 4
  },
  {
    "employees": [
      {
        "attributes": {
          "@employer_count": 1,
          "@employer_info": [
            {
              "company_name": "company2",
              "country_name": "chn"
            }
          ],
          "@employers": [
            "company2"
          ],
          "id": "person4",
          "interest_list": [
            "football"
          ],
          "interest_set": [
            "football"
          ],
          "location_id": "us",
          "skill_list": [
            4,
            1,
            10
          ],
          "skill_set": [
            4,
            1,
            10
          ]
        },
        "v_id": "person4",
        "v_type": "Person"
      },
      {
        "attributes": {
          "@employer_count": 2,
          "@employer_info": [
            {
              "company_name": "company2",
              "country_name": "chn"
            },
            {
              "company_name": "company1",
              "country_name": "us"
            }
          ],
          "@employers": [
            "company2",
            "company1"
          ],
          "id": "person1",
          "interest_list": [
            "management",
            "financial"
          ],
          "interest_set": [
            "management",
            "financial"
          ],
          "location_id": "us",
          "skill_list": [
            1,
            2,
            3
          ],
          "skill_set": [
            1,
            2,
            3
          ]
        },
        "v_id": "person1",
        "v_type": "Person"
      },
      {
        "attributes": {
          "@employer_count": 1,
          "@employer_info": [
            {
              "company_name": "company2",
              "country_name": "chn"
            }
          ],
          "@employers": [
            "company2"
          ],
          "id": "person5",
          "interest_list": [
            "sport",
            "financial",
            "engineering"
          ],
          "interest_set": [
            "sport",
            "financial",
            "engineering"
          ],
          "location_id": "can",
          "skill_list": [
            8,
            2,
            5
          ],
          "skill_set": [
            8,
            2,
            5
          ]
        },
        "v_id": "person5",
        "v_type": "Person"
      },
      {
        "attributes": {
          "@employer_count": 2,
          "@employer_info": [
            {
              "company_name": "company3",
              "country_name": "jp"
            },
            {
              "company_name": "company1",
              "country_name": "us"
            }
          ],
          "@employers": [
            "company3",
            "company1"
          ],
          "id": "person10",
          "interest_list": [
            "football",
            "sport"
          ],
          "interest_set": [
            "football",
            "sport"
          ],
          "location_id": "us",
          "skill_list": [
            3
          ],
          "skill_set": [
            3
          ]
        },
        "v_id": "person10",
        "v_type": "Person"
      },
      {
        "attributes": {
          "@employer_count": 2,
          "@employer_info": [
            {
              "company_name": "company2",
              "country_name": "chn"
            },
            {
              "company_name": "company3",
              "country_name": "jp"
            }
          ],
          "@employers": [
            "company2",
            "company3"
          ],
          "id": "person7",
          "interest_list": [
            "art",
            "sport"
          ],
          "interest_set": [
            "art",
            "sport"
          ],
          "location_id": "us",
          "skill_list": [
            8,
            6
          ],
          "skill_set": [
            8,
            6
          ]
        },
        "v_id": "person7",
        "v_type": "Person"
      },
      {
        "attributes": {
          "@employer_count": 1,
          "@employer_info": [
            {
              "company_name": "company1",
              "country_name": "us"
            }
          ],
          "@employers": [
            "company1"
          ],
          "id": "person6",
          "interest_list": [
            "music",
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