Data Types

An identifier is the name for an instance of a language element. In the GSQL query language, identifiers are used to name elements such as a query, a variable, or a user-defined function. In the EBNF syntax, an identifier is referred as name. It can be a sequence of letters, digits, or underscores ("_"). Other punctuation characters are not supported. The initial character can only be a letter or an underscore.

Different types of data can be used in different contexts. The EBNF syntax defines several classes of data types. The most basic is called base type (baseType). The other independent types are FILE and STRING COMPRESS. The remaining types are either compound data types built from the independent data types, or supersets of other types. The table below gives an overview of their definitions and their uses.

The query language supports the following base types, which can be declared and assigned anywhere within their scope. Any of these base types may be used when defining a global variable, a local variable, a query return value, a parameter, part of a tuple, or an element of a container accumulator. Accumulators are described in detail in a later section.

The default value of each base type is shown in the table below. The default value is the initial value of a base type variable (see Section "Variable Types" for more details), or the default return value for some functions.

The first seven types (INT, UINT, FLOAT, DOUBLE, BOOL, STRING, and DATETIME) are the same ones mentioned in the "Attribute Data Types" section of _GSQL Language Reference, Part 1.

Container types include the following data types:

To see how container type variables are declared in a GSQL query, see Local container variables.

A tuple is a user-defined data structure consisting of a fixed sequence of base type variables. Tuple types can be created and named using a TYPEDEF statement. Tuples must be defined first, before any other statements in a query.

A tuple can also be defined in a graph schema and then can be used as a vertex or edge attribute type. A tuple type that has been defined in the graph schema does not need to be re-defined in a query.

The vertex type person contains two complex attributes:

The query below reads both the SECRET_INFO tuple and the portfolio MAP. The tuple type does not need to be redefined in the query. To read and save the map, we define a MapAccum with the same types for key and value as the portfolio attribute. In addition, the query creates a new tuple type, ORDER_RECORD.

STRING COMPRESS is an integer type encoded by the system to represent string values. STRING COMPRESS uses less memory than STRING. The STRING COMPRESS type is designed to act like STRING: data are loaded and printed just as string data, and most functions and operators which take STRING input can also take STRING COMPRESS input. The difference is in how the data are stored internally. A STRING COMPRESS value can be obtained from a STRING_SET COMPRESS or STRING_LIST COMPRESS attribute or from converting a STRING value.

Using STRING COMPRESS instead of STRING can sometimes reduce storage space used, but results in slower access times. The storage space is only be smaller if:

Performance is always be slower compared to STRING; the slowdown is greater if the STRING COMPRESS attributes are accessed more often.

STRING COMPRESS type is beneficial for sets of string values when the same values are used multiple times. In practice, STRING COMPRESS are most useful for container accumulators like ListAccum<STRING COMPRESS> or SetAccum<STRING COMPRESS>.

An accumulator containing STRING COMPRESS stores the dictionary when it is assigned an attribute value or from another accumulator containing STRING COMPRESS. An accumulator containing STRING COMPRESS can store multiple dictionaries. A STRING value can be converted to a STRING COMPRESS value only if the value is in the dictionaries. If the STRING value is not in the dictionaries, the original string value is saved. A STRING COMPRESS value can be automatically converted to a STRING value.

When a STRING COMPRESS value is output (e.g. by a PRINT statement), it is shown as a STRING.

Below is an example query that uses the STRING COMPRESS type.

A FILE object is a sequential data storage object, associated with a text file on the local machine.

When a FILE object is declared, associated with a particular text file, any existing content in the text file will be erased. During the execution of the query, content written to the FILE will be appended to the FILE. When the query where the FILE was declared finishes running, the FILE contents are saved to the text file.

A FILE object can be passed as a parameter to another query. When a query receives a FILE object as a parameter, it can append data to that FILE, as can every other query which receives this FILE object as a parameter.

Input parameters to a query can be base type (except EDGE , JSONARRAY, or JSONOBJECT). A parameter can also be a SET or BAG which uses base type (except EDGE , JSONARRAY, or JSONOBJECT) as the element type. A FILE object can also be a parameter. Within the query, SET and BAG are converted to SetAccum and BagAccum, respectively.