SQL Functions

You can query the Space using built-in functions and user-defined functions.

Built-In Functions

For example, lets assume we have a class called Person with an Address property:

@SpaceClass
public class Person  {
    private UUID id;
    private String firstName;
    private String lastName;
    private Address address;
    
    @SpaceId
    public UUID getId() {
        return id;
    }
    ....
}        

public class Address {
    private String street;
    private String city;
    private String state;
    ......
}

We can query the Space with the built-in SQL functions:

// Find all persons with a firstName longer then tree characters
SQLQuery<Person> query = new SQLQuery<Person>(Person.class, "CHAR_LENGTH(firstName) > 3");
Person[] persons = space.readMultiple(query);

// Find all persons with a lastName length equal 22 or  25
SQLQuery<Person> query = new SQLQuery<Person>(Person.class, "CHAR_LENGTH(lastName) IN (22, 25");
Person[] persons = space.readMultiple(query); 

It is also possible to query for embedded properties:

// Find all persons with a city name greater then 6
query = new SQLQuery<Person>(Person.class, "CHAR_LENGTH(address.city) > 6");
Person[] persons = space.readMultiple(query);

// Find all persons with city name lenght 0 or 13
query = new SQLQuery<Person>(Person.class, "CHAR_LENGTH(address.city) IN (0,13)");
Person[] persons = space.readMultiple(query);
 

Supported SQL Functions

SQLQuery supports the following functions:

• ABS
• MOD
• ROUND
• CEIL, FLOOR
• CHAR_LENGTH
• LOWER, UPPER
• CONCAT, APPEND
• INSTR
• TO_NUMBER
• TO_CHAR (datetime), TO_CHAR (number)

For example, lets assume we have a class called Product with a Double property called price and a String property called name:

// An SQL query with ABS function,
// which will return all the entries that after ABS function are equal to 1 or 4
SQLQuery<Product> query = new SQLQuery<Product>(Product.class, "ABS(price) in (1, 4)");
Product[] products = gigaSpace.readMultiple(query);

// An SQL query with MOD function,
// which will return all the entries that after modulo 10 are equal to 6 or 7
SQLQuery<Product> query = new SQLQuery<Product>(Product.class, "MOD(price, 10) IN (6, 7)");
Product[] products = gigaSpace.readMultiple(query);

User-Defined Functions

User-defined functions (UDFs) , should be implemented in Java and can be called from any data access API that supports SQL Queries. This means, you can call them from a client using the Space API , JDBC API , .NET API , Rest API , JPA API , Scala API , UI , CLI, etc.

UDF allows you to access the relevant Space objects without serializing or materializing them. This means, the overall overhead of calling these functions is minimal. The SqlFunctionExecutionContext provides you direct access to the Space class properties. You can override existing functions such as ABS to perform customized functionality. Simply implement them as described below and register them using the ABS name.

Example

Here is an example of a user defined function:

import com.gigaspaces.query.sql.functions.SqlFunctionExecutionContext;

public class MyCustomSqlFunction extends SqlFunction {
    @Override
    public Object apply(SqlFunctionExecutionContext context) {
        // Increment by two before we return the value
        return (Double) context.getArgument(0) + 2;
    }
}

Space Registration

PLUSTWO is the new function that needs to be registered with the Space:

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns:os-core="http://www.openspaces.org/schema/core"
       xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
       http://www.openspaces.org/schema/core http://www.openspaces.org/schema/14.0/core/openspaces-core.xsd">

    <bean id="myCustomSqlFunction" class="sandbox.sqlcustomfunction.MyCustomSqlFunction" />
 
    <os-core:embedded-space id="space" space-name="mySpace">
        <os-core:space-sql-function name="PLUSTWO">
            <os-core:sql-function ref="myCustomSqlFunction" />
        </os-core:space-sql-function>
    </os-core:embedded-space>
    
    <os-core:giga-space id="gigaSpace" space="space"/>
</beans>

And here is the usage of the newly registered SQL function:

// An SQL query with PLUSTWO function,
// which will return all the entries that after PLUSTWO function are 20.0
SQLQuery<Product> query = new SQLQuery<Product>(Product.class, "PLUSTWO(price) = 20.0");
Product[] products = gigaSpace.readMultiple(query);

Limitations

• You cannot use a SQL function in combination with the collection index; you will get no results.
• parameter - The SQL function must get exactly one parameter that is a property of a POJO that is written to the Space and a number of unbound parameters that are not properties of a POJO.
• LRU - SQL functions are not supported with the LRU space caching policy.