How to integrate a new operator into Texera (from old wiki)

[chenlica]

From the page https://github.com/apache/texera/wiki/How-to-integrate-a-new-operator-into-Texera (may be dangling)

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Here we only talk about operator that does operation on retrieved data from source operator(e.g. sentiment analytics). This tutorial will not be suitable for source operator and result operator.

What to do on backend

Construct a predicate class

1. This class will be used to generate your operator object. It should extend from predicateBase. You need to add your predicate class to predicateBase file first.
2. The constructor of this predicate class should take all attributes you want your operator to take from the webpage(e.g. inputAttributeName/resultAttributeName), and store them.
3. For each parameter of constructor, you'll want a method to return this argument for your operator class to use.
4. The predicate class should have a newOperator method, which constructs and returns a new operator object using this predicate object. E.g. public dummyOperator newOperator() { return new dummyOperator(this); }
5. Write a getOperatorMetadata method to specify group and description of your operator. Use ImmutableMap.<~>builder to do it.

Construct a operator class

1. This class should extend from one of the classes from api/src/main/java/edu/uci/ics/texera/api/dataflow
2. This class should have a constructor which takes a predicate object and stores it.
3. This class should have a setInputOperator method, which specifies the previous operator(inputOperator).
4. This class should have a open method, which sets our inputSchema to be the inputOperator's ourputSchema and transforms our inputSchema into appropriate outputSchema. Then method open sets the cursor to OPENED.
5. This class should have a getNextTuple method, which calls getNextTuple of the inputOperator to get data from previous step; does operation on this data; adds generated field to the end if necessary; and returns the tuple.
6. This class should have a close method to set the cursor to CLOSED.
7. This class should have a transformToOutputSchema method, which takes inputSchema, modifies it, and returns the outputSchema.

Generate JsonSchema

1. Open dataflow/src/main/java/edu/uci/ics/texera/api/dataflow/common/JsonSchemaHelper.java
2. Comment the first line in main function
3. Uncomment the second line in main function
4. Change the parameter to your predicate class
5. Run it, a schema should appear in the directory of your predicate class

It is a good idea to write a test function for your operator in dataflow/src/main/java/edu/uci/ics/texera/api/dataflow/common/PredicateBaseTest.java

What to do on frontend

1. Add html element to core/gui/app/operatorbar/operator-bar.component.html, and set an unique id to it
2. Add relevant code to core/gui/app/services/mock-data.ts, remember to specify your operator's id at the bottom of the file
3. Add relevant code to dataflow/src/main/java/edu/uci/ics/texera/dataflow/plangen/OperatorArityConstants.java

Check the result

Use Running Texera GUI to compile and run backend/frontend