org.apache.spark.sql.catalyst.expressions.MonotonicallyIncreasingID.scala Maven / Gradle / Ivy
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package org.apache.spark.sql.catalyst.expressions
import org.apache.spark.sql.catalyst.InternalRow
import org.apache.spark.sql.catalyst.expressions.codegen.{CodegenContext, CodeGenerator, ExprCode, FalseLiteral}
import org.apache.spark.sql.catalyst.expressions.codegen.Block._
import org.apache.spark.sql.types.{DataType, LongType}
/**
* Returns monotonically increasing 64-bit integers.
*
* The generated ID is guaranteed to be monotonically increasing and unique, but not consecutive.
* The current implementation puts the partition ID in the upper 31 bits, and the lower 33 bits
* represent the record number within each partition. The assumption is that the data frame has
* less than 1 billion partitions, and each partition has less than 8 billion records.
*
* Since this expression is stateful, it cannot be a case object.
*/
@ExpressionDescription(
usage = """
_FUNC_() - Returns monotonically increasing 64-bit integers. The generated ID is guaranteed
to be monotonically increasing and unique, but not consecutive. The current implementation
puts the partition ID in the upper 31 bits, and the lower 33 bits represent the record number
within each partition. The assumption is that the data frame has less than 1 billion
partitions, and each partition has less than 8 billion records.
The function is non-deterministic because its result depends on partition IDs.
""")
case class MonotonicallyIncreasingID() extends LeafExpression with Stateful {
/**
* Record ID within each partition. By being transient, count's value is reset to 0 every time
* we serialize and deserialize and initialize it.
*/
@transient private[this] var count: Long = _
@transient private[this] var partitionMask: Long = _
override protected def initializeInternal(partitionIndex: Int): Unit = {
count = 0L
partitionMask = partitionIndex.toLong << 33
}
override def nullable: Boolean = false
override def dataType: DataType = LongType
override protected def evalInternal(input: InternalRow): Long = {
val currentCount = count
count += 1
partitionMask + currentCount
}
override def doGenCode(ctx: CodegenContext, ev: ExprCode): ExprCode = {
val countTerm = ctx.addMutableState(CodeGenerator.JAVA_LONG, "count")
val partitionMaskTerm = "partitionMask"
ctx.addImmutableStateIfNotExists(CodeGenerator.JAVA_LONG, partitionMaskTerm)
ctx.addPartitionInitializationStatement(s"$countTerm = 0L;")
ctx.addPartitionInitializationStatement(s"$partitionMaskTerm = ((long) partitionIndex) << 33;")
ev.copy(code = code"""
final ${CodeGenerator.javaType(dataType)} ${ev.value} = $partitionMaskTerm + $countTerm;
$countTerm++;""", isNull = FalseLiteral)
}
override def prettyName: String = "monotonically_increasing_id"
override def sql: String = s"$prettyName()"
override def freshCopy(): MonotonicallyIncreasingID = MonotonicallyIncreasingID()
}