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• 0.2.1
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ompute.logical-plan.0.2.1.source-code.LogicalPlan.kt Maven / Gradle / Ivy

package org.ballistacompute.logical

import org.ballistacompute.datatypes.Schema

/**
 * A logical plan represents a data transformation or action that returns a relation (a set of tuples).
 */
interface LogicalPlan {

    /**
     * Returns the schema of the data that will be produced by this logical plan.
     */
    fun schema(): Schema

    /**
     * Returns the children (inputs) of this logical plan. This method is used to enable use of the
     * visitor pattern to walk a query tree.
     */
    fun children(): List

    fun pretty(): String {
        return format(this)
    }
}

/** Format a logical plan in human-readable form */
fun format(plan: LogicalPlan, indent: Int = 0): String {
    val b = StringBuilder()
    0.until(indent).forEach { b.append("\t") }
    b.append(plan.toString()).append("\n")
    plan.children().forEach { b.append(format(it, indent+1)) }
    return b.toString()
}