pvary commented on code in PR #8553:
URL: https://github.com/apache/iceberg/pull/8553#discussion_r1401243005
##########
flink/v1.17/flink/src/main/java/org/apache/iceberg/flink/source/IcebergSource.java:
##########
@@ -453,6 +492,18 @@ public IcebergSource<T> build() {
contextBuilder.project(FlinkSchemaUtil.convert(icebergSchema,
projectedFlinkSchema));
}
+ SerializableRecordEmitter<T> emitter =
SerializableRecordEmitter.defaultEmitter();
+ if (watermarkColumn != null) {
Review Comment:
@dchristle: The code line is mostly irrelevant for the conversation 😄
Iceberg planner collects the files which should be scanned by the execution
engine, and creates `ScanTask`s from them. If a file is big, then it creates
multiple splits for a given file, so multiple readers could read the given file
parallel. OTOH if there are multiple small files, then it combines them to a
`CombinedScanTask` which are read by a single reader - this way decreasing the
number of splits, split assignments etc.
We generate a single watermark for every `ScanTask`. One `CombineScanTask`
could group multiple data files, with wide range of timestamps, so generating a
single watermark for it could be suboptimal. Setting
`read.split.open-file-cost` could prevent the creation such
`CombinedScanTask`s, and could result in better ordered input, and finer
grained watermarks.
##########
flink/v1.17/flink/src/main/java/org/apache/iceberg/flink/source/IcebergSource.java:
##########
@@ -453,6 +492,18 @@ public IcebergSource<T> build() {
contextBuilder.project(FlinkSchemaUtil.convert(icebergSchema,
projectedFlinkSchema));
}
+ SerializableRecordEmitter<T> emitter =
SerializableRecordEmitter.defaultEmitter();
+ if (watermarkColumn != null) {
Review Comment:
@dchristle: The code line is mostly irrelevant for the conversation 😄
Iceberg planner collects the files which should be scanned by the execution
engine, and creates `ScanTask`s from them. If a file is big, then it creates
multiple splits for a given file, so multiple readers could read the given file
parallel. OTOH if there are multiple small files, then it combines them to a
`CombinedScanTask` which are read by a single reader - this way decreasing the
number of splits, split assignments etc.
We generate a single watermark for every `ScanTask`. One `CombineScanTask`
could group multiple data files, with wide range of timestamps, so generating a
single watermark for it could be suboptimal. Setting
`read.split.open-file-cost` could prevent the creation such
`CombinedScanTask`s, and could result in better ordered input, and finer
grained watermarks.
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