rdblue commented on code in PR #5077:
URL: https://github.com/apache/iceberg/pull/5077#discussion_r906272469
##########
core/src/main/java/org/apache/iceberg/util/TableScanUtil.java:
##########
@@ -78,4 +86,71 @@ public static CloseableIterable<CombinedScanTask>
planTasks(CloseableIterable<Fi
splitFiles),
BaseCombinedScanTask::new);
}
+
+ @SuppressWarnings("unchecked")
+ public static <T extends ScanTask> CloseableIterable<ScanTaskGroup<T>>
planTaskGroups(CloseableIterable<T> tasks,
+
long splitSize, int lookback,
+
long openFileCost) {
+
+ Preconditions.checkArgument(splitSize > 0, "Invalid split size (negative
or 0): %s", splitSize);
+ Preconditions.checkArgument(lookback > 0, "Invalid split planning lookback
(negative or 0): %s", lookback);
+ Preconditions.checkArgument(openFileCost >= 0, "Invalid file open cost
(negative): %s", openFileCost);
+
+ // capture manifests which can be closed after scan planning
+ CloseableIterable<T> splitTasks = CloseableIterable.combine(
+ FluentIterable.from(tasks).transformAndConcat(task -> {
+ if (task instanceof SplittableScanTask<?>) {
+ return ((SplittableScanTask<? extends T>) task).split(splitSize);
+ } else {
+ return ImmutableList.of(task);
+ }
+ }),
+ tasks);
+
+ Function<T, Long> weightFunc = task -> Math.max(task.sizeBytes(),
task.filesCount() * openFileCost);
+
+ return CloseableIterable.transform(
+ CloseableIterable.combine(
+ new BinPacking.PackingIterable<>(splitTasks, splitSize, lookback,
weightFunc, true),
+ splitTasks),
+ combinedTasks -> new BaseScanTaskGroup<>(combineTasks(combinedTasks)));
+ }
+
+ @SuppressWarnings("unchecked")
+ public static <T extends ScanTask> List<T> combineTasks(List<T> tasks) {
Review Comment:
Maybe this should be called "merge" rather than "combine"? We use "combine"
to mean grouping tasks together, like in Hadoop. But this is actually creating
fewer tasks by merging them.
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