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Version: Java (Groovy)

How to create function-generated tables

This guide will show you how to create and use function-generated tables. As the name suggests, function-generated tables are tables generated by a user-defined Groovy function.

The FunctionGeneratedTableFactory's create method allows you to create ticking tables via a Groovy function. The ticking tables can be triggered by one or more source tables, or by a refresh interval.

Usage​

The basic syntax for create is as follows:

create(tableGenerator, sourceTables...)
create(tableGenerator, refreshIntervalMs)

The workflow for this method is to first define a function that returns a table, then pass it to create, which will re-run the with that function at pre-defined intervals based on either one or more source tables or a refresh interval.

If one or more source tables are used, the function will be re-run any time any of the tables tick. If a refresh interval is used, the function is re-run once per interval in milliseconds. You must only use one or the other as the trigger.

The user-defined table_generator function can source its data from anywhere - the only limit is the user's imagination, and the requirement that the function return a valid table.

Execution context​

The function_generated_table method requires an execution context to run in. If you don't specify an execution context, the method will use the systemic execution context. The examples below do not specify one, so the systemic execution context is used.

Define a tableGenerator function​

Next, we create a tableGenerator function. Transform your data any way you want - the only rule is that this function has to return a table.

Here's a simple example:

import io.deephaven.engine.context.ExecutionContext
import io.deephaven.util.SafeCloseable

// create execution context
defaultCtx = ExecutionContext.getContext()

// define tableGenerator function
tableGenerator = { ->
    Random rand = new Random()
    for (int i = 0; i < 5; ++i) {
        try (SafeCloseable ignored = defaultCtx.open()) {
            myTable = emptyTable(5).update("X = randomInt(0, 10)", "Y = randomDouble(0.0, 100.0)")
        }
        sleep(10)
    }
    return myTable
}

Generate tables with a Groovy function​

Now, we'll create two function-generated tables: one that re-runs the tableGenerator whenever the source table updates, and one that re-runs the tableGenerator function every 2000ms.

import io.deephaven.engine.context.ExecutionContext
import io.deephaven.util.SafeCloseable
import io.deephaven.engine.table.impl.util.FunctionGeneratedTableFactory

// create execution context
defaultCtx = ExecutionContext.getContext()

// define tableGenerator function
tableGenerator = { ->
    Random rand = new Random()
    for (int i = 0; i < 5; ++i) {
        try (SafeCloseable ignored = defaultCtx.open()) {
            myTable = emptyTable(5).update("X = randomInt(0, 10)", "Y = randomDouble(0.0, 100.0)")
        }
        sleep(10)
    }
    return myTable
}

// Create a time table
timeTable1 = timeTable("PT1S")

// create a function-generated table that re-runs tableGenerator every 2000ms
resultTime = FunctionGeneratedTableFactory.create(tableGenerator, 2000)

// create a function-generated table that re-runs tableGenerator whenever timeTable1 ticks
resultTick = FunctionGeneratedTableFactory.create(tableGenerator, timeTable1)