Github user nongli commented on a diff in the pull request:
https://github.com/apache/spark/pull/11065#discussion_r51954333
--- Diff:
sql/core/src/main/scala/org/apache/spark/sql/execution/joins/HashedRelation.scala
---
@@ -408,6 +453,210 @@ private[joins] object UnsafeHashedRelation {
}
}
+ // TODO: create UniqueUnsafeRelation
new UnsafeHashedRelation(hashTable)
}
}
+
+/**
+ * An interface for a hashed relation that the key is a Long.
+ */
+private[joins] trait LongHashedRelation extends HashedRelation {
+ override def get(key: InternalRow): Seq[InternalRow] = {
+ get(key.getLong(0))
+ }
+}
+
+private[joins] final class GeneralLongHashedRelation(
+ private var hashTable: JavaHashMap[Long, CompactBuffer[UnsafeRow]])
+ extends LongHashedRelation with Externalizable {
+
+ // Needed for serialization (it is public to make Java serialization
work)
+ def this() = this(null)
+
+ override def get(key: Long): Seq[InternalRow] = hashTable.get(key)
+
+ override def writeExternal(out: ObjectOutput): Unit = {
+ writeBytes(out, SparkSqlSerializer.serialize(hashTable))
+ }
+
+ override def readExternal(in: ObjectInput): Unit = {
+ hashTable = SparkSqlSerializer.deserialize(readBytes(in))
+ }
+}
+
+private[joins] final class UniqueLongHashedRelation(
+ private var hashTable: JavaHashMap[Long, UnsafeRow])
+ extends UniqueHashedRelation with LongHashedRelation with Externalizable
{
+
+ // Needed for serialization (it is public to make Java serialization
work)
+ def this() = this(null)
+
+ override def getValue(key: InternalRow): InternalRow = {
+ getValue(key.getLong(0))
+ }
+
+ override def getValue(key: Long): InternalRow = {
+ hashTable.get(key)
+ }
+
+ override def writeExternal(out: ObjectOutput): Unit = {
+ writeBytes(out, SparkSqlSerializer.serialize(hashTable))
+ }
+
+ override def readExternal(in: ObjectInput): Unit = {
+ hashTable = SparkSqlSerializer.deserialize(readBytes(in))
+ }
+}
+
+/**
+ * A relation that pack all the rows into a byte array, together with
offsets and sizes.
+ */
+private[joins] final class LongArrayRelation(
+ private var numFields: Int,
+ private var start: Long,
+ private var offsets: Array[Int],
+ private var sizes: Array[Int],
+ private var bytes: Array[Byte]
+ ) extends UniqueHashedRelation with LongHashedRelation with
Externalizable {
+
+ // Needed for serialization (it is public to make Java serialization
work)
+ def this() = this(0, 0L, null, null, null)
+
+ override def getValue(key: InternalRow): InternalRow = {
+ getValue(key.getLong(0))
+ }
+
+ override def getMemorySize: Long = {
+ offsets.length * 4 + sizes.length * 4 + bytes.length
+ }
+
+ override def getValue(key: Long): InternalRow = {
+ val idx = (key - start).toInt
+ if (idx >= 0 && idx < sizes.length && sizes(idx) > 0) {
+ val result = new UnsafeRow(numFields)
+ result.pointTo(bytes, Platform.BYTE_ARRAY_OFFSET + offsets(idx),
sizes(idx))
+ result
+ } else {
+ null
+ }
+ }
+
+ override def writeExternal(out: ObjectOutput): Unit = {
+ out.writeInt(numFields)
+ out.writeLong(start)
+ out.writeInt(sizes.length)
+ var i = 0
+ while (i < sizes.length) {
+ out.writeInt(sizes(i))
+ i += 1
+ }
+ out.writeInt(bytes.length)
+ out.write(bytes)
+ }
+
+ override def readExternal(in: ObjectInput): Unit = {
+ numFields = in.readInt()
+ start = in.readLong()
+ val length = in.readInt()
+ // read sizes of rows
+ sizes = new Array[Int](length)
+ offsets = new Array[Int](length)
+ var i = 0
+ var offset = 0
+ while (i < length) {
+ offsets(i) = offset
+ sizes(i) = in.readInt()
+ offset += sizes(i)
+ i += 1
+ }
+ // read all the bytes
+ val total = in.readInt()
+ assert(total == offset)
+ bytes = new Array[Byte](total)
+ in.readFully(bytes)
+ }
+}
+
+/**
+ * Create hashed relation with key that is long.
--- End diff --
Document this better. Explain at a high level the strategy this is using.
How it looks for unique dense keys, etc.
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