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Version: Java (Groovy)

Partitioned table transform

transform applies a unary operator to all constituents of a partitioned table.

Syntax​

transform(UnaryOperator<Table> transformer)
transform(ExecutionContext executionContext, UnaryOperator<Table> transformer, boolean expectRefreshingResults)

Parameters​

ParameterTypeDescription
transformerUnaryOperator<Table>

An operation on a table that returns a table.

executionContextExecutionContext

The ExecutionContext to use for the transformation.

expectRefreshingResultsboolean

Whether to expect refreshing results from the transformation. If true, the resulting partitioned table will always be backed by a refreshing table. This is important for transforms applied to static inputs that may produce refreshing output, because it ensures correct liveness management. Incorrectly specifying false will result in exceptions.

Returns​

A PartitionedTable.

Examples​

This first example applies a transformation to add a new column to each constituent of a partitioned table.

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

source = emptyTable(5).update("IntCol = i", "StrCol = `value`")
result = source.partitionBy("IntCol")

ctx = ExecutionContext.getContext()

addOne = { t ->
    try (SafeCloseable ignored = ctx.open()) {
        return t.update("IntCol2 = IntCol + 1")
    }
}

result2 = result.transform(addOne)

newConstituent = result2.constituentFor(3)

This second example applies aggregations to each constituent of a partitioned table via transform. It specifies the execution context in the transform call, so no it is not needed in the closure. Additionally, refreshing results are not expected, so false is passed as the third argument.

import static io.deephaven.api.agg.Aggregation.AggCount
import static io.deephaven.api.agg.Aggregation.AggAvg
import static io.deephaven.api.agg.Aggregation.AggSum
import io.deephaven.engine.context.ExecutionContext

import org.apache.commons.lang.RandomStringUtils

Random random = new Random()

randSymbol = { ->
    return RandomStringUtils.random(1, 'ABCDE')
}

source = emptyTable(100).update("Sym = (String)randSymbol()", "X = randomInt(0, 100)", "Y = randomDouble(-50.0, 50.0)")

ctx = ExecutionContext.getContext()

applyAggs = { t ->
    return t.update("Z = X % 5").aggBy([AggSum("SumX = X"), AggCount("Z"), AggAvg("AvgY = Y")], "Sym")
}

partitionedSource = source.partitionBy("Sym")

partitionedResult = partitionedSource.transform(ctx, applyAggs, false)

result3 = partitionedResult.constituentFor("A")