danielcweeks commented on code in PR #7688:
URL: https://github.com/apache/iceberg/pull/7688#discussion_r1206095696
##########
core/src/main/java/org/apache/iceberg/BaseScan.java:
##########
@@ -256,4 +265,95 @@ private static Schema
lazyColumnProjection(TableScanContext context, Schema sche
public ThisT metricsReporter(MetricsReporter reporter) {
return newRefinedScan(table(), schema(), context().reportWith(reporter));
}
+
+ private Optional<Long> adaptiveSplitSize(long tableSplitSize) {
+ if (!PropertyUtil.propertyAsBoolean(
+ table.properties(),
+ TableProperties.ADAPTIVE_SPLIT_PLANNING,
+ TableProperties.ADAPTIVE_SPLIT_PLANNING_DEFAULT)) {
+ return Optional.empty();
+ }
+
+ int minParallelism =
+ PropertyUtil.propertyAsInt(
+ table.properties(),
+ TableProperties.SPLIT_MIN_PARALLELISM,
+ TableProperties.SPLIT_MIN_PARALLELISM_DEFAULT);
+
+ Preconditions.checkArgument(minParallelism > 0, "Minimum parallelism must
be a positive value");
+
+ Snapshot snapshot =
+ Stream.of(context.snapshotId(), context.toSnapshotId())
+ .filter(Objects::nonNull)
+ .map(table::snapshot)
+ .findFirst()
+ .orElseGet(table::currentSnapshot);
+
+ if (snapshot == null || snapshot.summary() == null) {
+ return Optional.empty();
+ }
+
+ Map<String, String> summary = snapshot.summary();
+ long totalFiles =
+ PropertyUtil.propertyAsLong(summary,
SnapshotSummary.TOTAL_DATA_FILES_PROP, 0);
+ long totalSize = PropertyUtil.propertyAsLong(summary,
SnapshotSummary.TOTAL_FILE_SIZE_PROP, 0);
+
+ if (totalFiles <= 0 || totalSize <= 0) {
+ return Optional.empty();
+ }
+
+ if (totalFiles > minParallelism && totalSize >= tableSplitSize *
minParallelism) {
+ // If it is possible that splits could normally be calculated to meet the
+ // minimum parallelism, do not adjust the split size
+ return Optional.empty();
+ }
+
+ FileFormat fileFormat =
+ FileFormat.fromString(
+ table
+ .properties()
+ .getOrDefault(
+ TableProperties.DEFAULT_FILE_FORMAT,
+ TableProperties.DEFAULT_FILE_FORMAT_DEFAULT));
+
+ if (!fileFormat.isSplittable()) {
+ return Optional.of(totalSize / totalFiles);
+ }
+
+ long rowGroupSize;
+
+ switch (fileFormat) {
+ case PARQUET:
+ rowGroupSize =
+ PropertyUtil.propertyAsLong(
+ table.properties(),
+ TableProperties.PARQUET_ROW_GROUP_SIZE_BYTES,
+ TableProperties.PARQUET_ROW_GROUP_SIZE_BYTES_DEFAULT);
+ break;
+ case ORC:
+ rowGroupSize =
+ PropertyUtil.propertyAsLong(
+ table.properties(),
+ TableProperties.ORC_BLOCK_SIZE_BYTES,
+ TableProperties.ORC_BLOCK_SIZE_BYTES_DEFAULT);
+ break;
+ case AVRO:
+ rowGroupSize = 16 * 1024 * 1024;
+ break;
+ default:
+ rowGroupSize = tableSplitSize;
+ }
+
+ if (totalFiles <= 1) {
+ // For a table with a single small file, default to the smallest of
+ // the configured table split size or the format block size
+ return Optional.of(Math.min(rowGroupSize, tableSplitSize));
+ }
+
+ long minSplitSize = totalSize / minParallelism;
+ // target split size chosen to provide the most parallelism
+ long targetSplitSize = Math.min(minSplitSize, rowGroupSize);
+
+ return Optional.of(targetSplitSize);
Review Comment:
I don't think that's generally going to be the case. Combining still
happens and I'm not clear there's a situation where too many splits will be
produced.
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