[hail] new aggregator path for TableAggregateByKey (#7195)

* [hail] new aggregator path for TableAggregateByKey

* bump

hail/src/main/scala/is/hail/expr/ir/TableIR.scala

@@ -1476,6 +1476,106 @@ case class TableAggregateByKey(child: TableIR, expr: IR) extends TableIR {
     val prev = child.execute(ctx)
     val prevRVD = prev.rvd
 
+    if (HailContext.getFlag("newaggs") != null) {
+      try {
+        val res = genUID()
+        val extracted = agg.Extract(expr, res)
+
+        val (_, makeInit) = ir.CompileWithAggregators2[Long, Unit](
+          extracted.aggs,
+          "global", prev.globals.t,
+          extracted.init)
+
+        val (_, makeSeq) = ir.CompileWithAggregators2[Long, Long, Unit](
+          extracted.aggs,
+          "global", prev.globals.t,
+          "row", prev.rvd.rowPType,
+          extracted.seqPerElt)
+
+        val valueIR = Let(res, extracted.results, extracted.postAggIR)
+        val keyType = PType.canonical(prev.typ.keyType).asInstanceOf[PStruct]
+        val key = Ref(genUID(), keyType.virtualType)
+        val value = Ref(genUID(), valueIR.typ)
+        val (rowType: PStruct, makeRow) = ir.CompileWithAggregators2[Long, Long, Long](
+          extracted.aggs,
+          "global", prev.globals.t,
+          key.name, keyType,
+          Let(value.name, valueIR,
+            InsertFields(key, typ.valueType.fieldNames.map(n => n -> GetField(value, n)))))
+        assert(rowType.virtualType == typ.rowType, s"$rowType, ${ typ.rowType }")
+
+        val localChildRowType = prevRVD.rowPType
+        val keyIndices = prev.typ.keyFieldIdx
+        val keyOrd = prevRVD.typ.kRowOrd
+        val globalsBc = prev.globals.broadcast
+
+        val newRVDType = prevRVD.typ.copy(rowType = rowType)
+
+        val newRVD = prevRVD
+          .repartition(prevRVD.partitioner.strictify)
+          .boundary
+          .mapPartitionsWithIndex(newRVDType, { (i, ctx, it) =>
+            val partRegion = ctx.freshRegion
+
+            val globalsOff = globalsBc.value.readRegionValue(partRegion)
+
+            val initialize = makeInit(i, partRegion)
+            val sequence = makeSeq(i, partRegion)
+            val newRowF = makeRow(i, partRegion)
+
+            val aggRegion = ctx.freshRegion
+
+            new Iterator[RegionValue] {
+              var isEnd = false
+              var current: RegionValue = _
+              val rowKey: WritableRegionValue = WritableRegionValue(keyType, ctx.freshRegion)
+              val consumerRegion: Region = ctx.region
+              val newRV = RegionValue(consumerRegion)
+
+              def hasNext: Boolean = {
+                if (isEnd || (current == null && !it.hasNext)) {
+                  isEnd = true
+                  return false
+                }
+                if (current == null)
+                  current = it.next()
+                true
+              }
+
+              def next(): RegionValue = {
+                if (!hasNext)
+                  throw new java.util.NoSuchElementException()
+
+                rowKey.setSelect(localChildRowType, keyIndices, current)
+                val region = current.region
+
+                aggRegion.clear()
+                initialize.newAggState(aggRegion)
+                initialize(region, globalsOff, false)
+                sequence.setAggState(aggRegion, initialize.getAggOffset())
+
+                do {
+                  val region = current.region
+                  sequence(region,
+                    globalsOff, false,
+                    current.offset, false)
+                  current = null
+                } while (hasNext && keyOrd.equiv(rowKey.value, current))
+                newRowF.setAggState(aggRegion, sequence.getAggOffset())
+                newRV.setOffset(newRowF(consumerRegion, globalsOff, false, rowKey.offset, false))
+                newRV
+              }
+            }
+          })
+
+        return prev.copy(rvd = newRVD, typ = typ)
+
+      } catch {
+        case e: agg.UnsupportedExtraction =>
+          log.info(s"couldn't lower TableAggregate: $e")
+      }
+    }
+
     val (rvAggs, makeInit, makeSeq, aggResultType, postAggIR) = ir.CompileWithAggregators[Long, Long, Long](
       "global", prev.globals.t,
       "global", prev.globals.t,