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Senthil Nathan
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Changes done for v1.0.4.
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‎CHANGELOG.md‎

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# Changes
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## v1.0.4
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* Apr/23/2021
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* Added a new function get_tuple_attribute_value to fetch the value of a user given attribute name if present in a user given tuple.
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## v1.0.3
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* Apr/20/2021
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* Added more special operations for rstring, set, list and map. They are sizeEQ, sizeNE, sizeLT, sizeLE, sizeGT and sizeGE.

‎README.md‎

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## Purpose
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This toolkit offers an improved and a simpler facility for users to let their externally authored business rules to be consumed either statically or dynamically from within the IBM Streams SPL application code and then process (evaluate) them as the data flows through the application pipeline. Such an evaluation returns a true or false result for every rule that gets processed to indicate whether the rule expression criteria is met or not met.
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## Main feature
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## Major features
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It provides the following function that can be called from within the IBM Streams application code. This function is designed to use internal in-memory caching in order to be optimal when processing a rule that gets evaluated frequently inside a given IBM Streams Custom operator logic. Such caching is done on a per PE i.e. Linux process thread basis. In addition, it uses C++ reference pointers wherever possible to reduce the overall rule processing time by avoiding unnecessary data copy that can get expensive.
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**eval_predicate** is a C++ native function provided via this toolkit. IBM Streams applications can add this toolkit as a dependency either via the -t Streams compiler option or by adding this toolkit directory path in the Streams Studio and/or the Microsoft Visual Studio Code. Once the dependency is in place, this function can be called from wherever it is needed within the application code.
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// It returns a non-zero error when there is an evaluation execution failure.
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```
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**get_tuple_attribute_value** is another C++ native function provided via this toolkit. This function fetches the value of a user given attribute name if present in a user given tuple. Any valid fully qualified attribute name can be given via a input string argument to this function.
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```
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// This namespace usage declaration is needed at the top of an application.
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use com.ibm.streamsx.eval_predicate::*;
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// Schema can include other deeply nested types.
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type Person_t = rstring name, rstring title,
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int32 id, rstring gender, set<rstring> skills;
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type Department_t = rstring name, rstring id,
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rstring manager, int32 employeeCnt;
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type Employee_t = Person_t employee, Department_t department;
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// Let us say that an incoming tuple holds the values as shown below.
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mutable Employee_t myEmployee = {};
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myEmployee.employee.name = "Jill Doe";
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myEmployee.employee.title = "Software Engineer";
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myEmployee.employee.id = 452397;
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myEmployee.employee.gender = "Female";
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myEmployee.employee.skills = {"C++", "Java", "Python", "SPL"};
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myEmployee.department.name = "Process Optimization";
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myEmployee.department.id = "XJ825";
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myEmployee.department.manager = "Mary Williams";
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myEmployee.department.employeeCnt = 18;
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// Following code snippet shows how a Custom operator logic
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// can fetch the value of a given tuple attribute.
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mutable int32 error = 0;
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// Get the full set<rstring> value of a given tuple attribute name.
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rstring attributeName = "employee.skills";
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mutable set<rstring> employeeSkills = {};
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get_tuple_attribute_value(attributeName, myEmployee,
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employeeSkills, error, false);
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if(error == 0) {
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printStringLn("Tuple attribute value was fetched successfully.");
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printStringLn(attributeName + "=" + (rstring)employeeSkills);
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} else {
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printStringLn("Tuple attribute value was not fetched successfully. Error=" + (rstring)error);
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}
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// Following is the usage description for the get_tuple_attribute_value function.
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//
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// Arg1: Fully qualified attribute name
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// Arg2: Your tuple
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// Arg3: A mutable variable of an appropriate type in which the
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// value of a given attribute will be returned.
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// Arg4: A mutable int32 variable to receive non-zero error code if any.
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// Arg5: A boolean value to enable debug tracing inside this function.
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// It is a void function that returns nothing.
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```
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## Design considerations
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This toolkit came into existence for a specific need with which a large enterprise customer approached the author of this toolkit. There is already a built-in function named *evalPredicate* that is available in the official IBM Streams product. However, that function has certain limitations. To fill that gap, this toolkit with its own **eval_predicate** function is being made available freely via the publicly accessible IBMStreams GitHub. The **eval_predicate** function from this toolkit differs from the *evalPredicate* built-in function in the IBM Streams product in the following ways.
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‎com.ibm.streamsx.eval_predicate/EvalPredicateExample.spl‎

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/*
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==================================================================
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First created on: Mar/05/2021
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Last modified on: Apr/18/2021
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Last modified on: Apr/23/2021
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This is an example application that shows how to use the
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eval_predicate function to evaluate an SPL expression a.k.a
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((a == "hi" || c endsWith 'pqr') && (b contains "xyz")) || (g[4] > 6.7 || id % 8 == 3)
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(((a == 'hi') || (x <= 5) || (t == 3.14) || (p > 7)) && ((j == 3) && (y < 1) && (r == 9)) && s endsWith 'Nation')
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In addition to showing how to do rule expression processing,
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this example also shows another feature of the eval_predicate
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toolkit i.e. how to get a value of a specific tuple attribute as
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that is expressed via a user provided string input.
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In this example, you can search for get_tuple_attribute_value to
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see 10 different test cases on that topic.
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How can you use this new eval_predicate function?
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-------------------------------------------------
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Any other application that wants to use this function must
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expression<boolean> $EVAL_PREDICATE_TRACING :
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(boolean)getSubmissionTimeValue("EvalPredicateTracing", "false");
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// This constant can be used to specify whether the
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// value of the tuple attribute fetched via the
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// get_tuple_attribute_value should be displayed on
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// the console or not.
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expression<boolean> $DISPLAY_FETCHED_ATTRIBUTE_VALUE :
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(boolean)getSubmissionTimeValue("DisplayFetchedAttributeValue", "true");
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type
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// These are types or schema of the tuples that we will use to
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// evaluate different kinds of expressions.
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logic
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onTuple S: {
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mutable rstring rule = "";
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mutable rstring attributeName = "";
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mutable int32 error = 0;
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mutable boolean result = false;
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} else {
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printStringLn("Testcase 2.4: Evaluation execution failed. Error=" + (rstring)error);
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}
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// Get the value of a given tuple attribute name.
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// Arg1: Fully qualified attribute name
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// Arg2: Your tuple
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// Arg3: A mutable variable of an appropriate type in which the
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// value of a given attribute will be returned.
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// Arg4: A mutable int32 variable to receive non-zero error code if any.
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// Arg5: A boolean value to enable debug tracing inside this function.
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// It is a void method that returns nothing.
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//
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// 2.5
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// Get an int32 value of a given tuple attribute name.
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attributeName = "employee.id";
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mutable int32 employeeId = 0;
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get_tuple_attribute_value(attributeName, myEmployee,
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employeeId, error, $EVAL_PREDICATE_TRACING);
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if(error == 0) {
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printStringLn("Testcase 2.5: Tuple attribute value was fetched successfully.");
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if($DISPLAY_FETCHED_ATTRIBUTE_VALUE == true) {
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printStringLn(attributeName + "=" + (rstring)employeeId);
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}
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} else {
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printStringLn("Testcase 2.5: Tuple attribute value was not fetched successfully. Error=" + (rstring)error);
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}
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// 2.6
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// Get the full set<rstring> value of a given tuple attribute name.
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attributeName = "employee.skills";
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mutable set<rstring> employeeSkills = {};
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get_tuple_attribute_value(attributeName, myEmployee,
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employeeSkills, error, $EVAL_PREDICATE_TRACING);
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if(error == 0) {
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printStringLn("Testcase 2.6: Tuple attribute value was fetched successfully.");
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if($DISPLAY_FETCHED_ATTRIBUTE_VALUE == true) {
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printStringLn(attributeName + "=" + (rstring)employeeSkills);
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}
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} else {
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printStringLn("Testcase 2.6: Tuple attribute value was not fetched successfully. Error=" + (rstring)error);
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}
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// ============== TESTCASE GROUP 3 ==============
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mutable City_t myCity = {};
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} else {
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printStringLn("Testcase 3.13: Evaluation execution failed. Error=" + (rstring)error);
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}
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// Get the value of a given tuple attribute name.
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// Arg1: Fully qualified attribute name
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// Arg2: Your tuple
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// Arg3: A mutable variable of an appropriate type in which the
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// value of a given attribute will be returned.
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// Arg4: A mutable int32 variable to receive non-zero error code if any.
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// Arg5: A boolean value to enable debug tracing inside this function.
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// It is a void method that returns nothing.
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//
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// 3.14
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// Get an rstring value of a given tuple attribute name.
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attributeName = "name";
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mutable rstring cityName = "";
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get_tuple_attribute_value(attributeName, myCity,
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cityName, error, $EVAL_PREDICATE_TRACING);
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if(error == 0) {
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printStringLn("Testcase 3.14: Tuple attribute value was fetched successfully.");
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if($DISPLAY_FETCHED_ATTRIBUTE_VALUE == true) {
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printStringLn(attributeName + "=" + (rstring)cityName);
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}
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} else {
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printStringLn("Testcase 3.14: Tuple attribute value was not fetched successfully. Error=" + (rstring)error);
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}
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// 3.15
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// Get a float32 value of a given tuple attribute name.
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attributeName = "details.location.geo.latitude";
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mutable float32 latitude = (float32)0.0;
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get_tuple_attribute_value(attributeName, myCity,
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latitude, error, $EVAL_PREDICATE_TRACING);
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if(error == 0) {
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printStringLn("Testcase 3.15: Tuple attribute value was fetched successfully.");
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if($DISPLAY_FETCHED_ATTRIBUTE_VALUE == true) {
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printStringLn(attributeName + "=" + (rstring)latitude);
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}
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} else {
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printStringLn("Testcase 3.15: Tuple attribute value was not fetched successfully. Error=" + (rstring)error);
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}
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// 3.16
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// Get a list<rstring>[idx] value of a given tuple attribute name.
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attributeName = "details.location.info.businesses[2]";
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mutable rstring businessName = "";
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get_tuple_attribute_value(attributeName, myCity,
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businessName, error, $EVAL_PREDICATE_TRACING);
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if(error == 0) {
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printStringLn("Testcase 3.16: Tuple attribute value was fetched successfully.");
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if($DISPLAY_FETCHED_ATTRIBUTE_VALUE == true) {
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printStringLn(attributeName + "=" + (rstring)businessName);
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}
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} else {
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printStringLn("Testcase 3.16: Tuple attribute value was not fetched successfully. Error=" + (rstring)error);
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}
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// 3.17
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// Get a map<rstring,rstring>[key] value of a given tuple attribute name.
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attributeName = "details.location.info.officials['Mayor']";
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mutable rstring mayor = "";
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get_tuple_attribute_value(attributeName, myCity,
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mayor, error, $EVAL_PREDICATE_TRACING);
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if(error == 0) {
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printStringLn("Testcase 3.17: Tuple attribute value was fetched successfully.");
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if($DISPLAY_FETCHED_ATTRIBUTE_VALUE == true) {
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printStringLn(attributeName + "=" + (rstring)mayor);
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}
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} else {
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printStringLn("Testcase 3.17: Tuple attribute value was not fetched successfully. Error=" + (rstring)error);
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}
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// 3.18
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// Get the entire list<rstring> value of a given tuple attribute name.
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attributeName = "roadwayNumbers";
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mutable list<int32> routeNumbers = [];
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get_tuple_attribute_value(attributeName, myCity,
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routeNumbers, error, $EVAL_PREDICATE_TRACING);
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if(error == 0) {
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printStringLn("Testcase 3.18: Tuple attribute value was fetched successfully.");
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673+
if($DISPLAY_FETCHED_ATTRIBUTE_VALUE == true) {
674+
printStringLn(attributeName + "=" + (rstring)routeNumbers);
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}
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} else {
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printStringLn("Testcase 3.18: Tuple attribute value was not fetched successfully. Error=" + (rstring)error);
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}
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// 3.19
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// Get the entire map<rstring,rstring> value of a given tuple attribute name.
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attributeName = "housingNumbers";
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mutable map<rstring,int32> housingReport = {};
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get_tuple_attribute_value(attributeName, myCity,
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housingReport, error, $EVAL_PREDICATE_TRACING);
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if(error == 0) {
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printStringLn("Testcase 3.19: Tuple attribute value was fetched successfully.");
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if($DISPLAY_FETCHED_ATTRIBUTE_VALUE == true) {
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printStringLn(attributeName + "=" + (rstring)housingReport);
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}
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} else {
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printStringLn("Testcase 3.19: Tuple attribute value was not fetched successfully. Error=" + (rstring)error);
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}
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// ============== TESTCASE GROUP 4 ==============
529698
mutable AccuWeather_t myWeather = {};
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myWeather.city = "New York";
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583752
printStringLn("Testcase 4.2: Evaluation execution failed. Error=" + (rstring)error);
584753
}
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// Get the value of a given tuple attribute name.
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// Arg1: Fully qualified attribute name
757+
// Arg2: Your tuple
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// Arg3: A mutable variable of an appropriate type in which the
759+
// value of a given attribute will be returned.
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// Arg4: A mutable int32 variable to receive non-zero error code if any.
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// Arg5: A boolean value to enable debug tracing inside this function.
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// It is a void method that returns nothing.
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//
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// 4.3
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// Get a list<TUPLE>[idx] value of a given tuple attribute name.
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attributeName = "weatherList[0].hourlyTemperatureMap";
767+
mutable map<int64, float64> myTemperatureMap = {};
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get_tuple_attribute_value(attributeName, accuWeatherTestData,
769+
myTemperatureMap, error, $EVAL_PREDICATE_TRACING);
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771+
if(error == 0) {
772+
printStringLn("Testcase 4.3: Tuple attribute value was fetched successfully.");
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774+
if($DISPLAY_FETCHED_ATTRIBUTE_VALUE == true) {
775+
printStringLn(attributeName + "=" + (rstring)myTemperatureMap);
776+
}
777+
} else {
778+
printStringLn("Testcase 4.3: Tuple attribute value was not fetched successfully. Error=" + (rstring)error);
779+
}
780+
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// 4.4
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// Get the entire list<TUPLE> value of a given tuple attribute name.
783+
attributeName = "weatherList";
784+
mutable list<AccuWeather_t> myWeatherList = [];
785+
get_tuple_attribute_value(attributeName, accuWeatherTestData,
786+
myWeatherList, error, $EVAL_PREDICATE_TRACING);
787+
788+
if(error == 0) {
789+
printStringLn("Testcase 4.4: Tuple attribute value was fetched successfully.");
790+
791+
if($DISPLAY_FETCHED_ATTRIBUTE_VALUE == true) {
792+
printStringLn(attributeName + "=" + (rstring)myWeatherList);
793+
}
794+
} else {
795+
printStringLn("Testcase 4.4: Tuple attribute value was not fetched successfully. Error=" + (rstring)error);
796+
}
586797
} // End of onTuple S
587798
} // End of the Custom operator.
588799
} // End of the main composite.

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