create

The FunctionGeneratedTableFactory's create method is useful for creating tables that are dependent on one or more ticking tables, or for creating tables that need to be refreshed at a regular interval. The method creates a table by running the user-defined tableGenerator function. This function will be run once when the table is created, and then again when either the sourceTables... tick or when refreshIntervalMs milliseconds have elapsed.

note

The tableGenerator may access data in the sourceTables, but should not perform any further operations on them without careful handling. Since table operations may be memoized, a table operation may return a table created by a previous invocation of the same operation. Since that result will not have been included in the sourceTables, it is not automatically treated as a dependency for purposes of determining when it is safe to invoke tableGenerator. This allows race conditions to exist between accessing the operation result and that result's own update processing. It is best to include all dependencies directly in sourceTables or only compute on-demand inputs under a LivenessScope.

When transforming a table, users should generally prefer to use regular table operations instead of this factory because they can perform some operations incrementally. However, create might require less development effort for small tables.

Syntax

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

Parameters

Parameter	Type	Description
tableGenerator	Supplier<Table>	A function that returns a table to copy into the output table.
refreshIntervalMs	int	The interval (in milliseconds) at which the tableGenerator function is re-run.
sourceTables	Table...	If the tableGenerator function is dependent on one or more ticking tables, the tables must be specified here. This will cause the generated table to be recomputed on each tick.

Returns

A ticking table (assuming sourceTables have been specified), generated by the tableGenerator function.

Example

In the following example, we create an execution context and a tableGenerator function, which we then use to generate a table 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 function-generated table that re-runs tableGenerator every 2000ms
result = FunctionGeneratedTableFactory.create(tableGenerator, 2000)

result

If the tableGenerator function depends on one or more ticking tables, the tables must be specified. Adding timeTable1 as a sourceTables... parameter causes the generated table to be recomputed on each tick of the time table.

import io.deephaven.engine.context.ExecutionContext
import io.deephaven.csv.util.MutableBoolean
import io.deephaven.engine.table.ColumnDefinition
import io.deephaven.engine.table.TableDefinition
import io.deephaven.stream.TablePublisher
import io.deephaven.util.SafeCloseable
import io.deephaven.engine.table.impl.util.FunctionGeneratedTableFactory

defaultCtx = ExecutionContext.getContext()

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
}

timeTable1 = timeTable("PT1S")

result = FunctionGeneratedTableFactory.create(tableGenerator, timeTable1)

result

Related documentation

• Execution Context
• Javadoc