lucasfang commented on code in PR #286:
URL: https://github.com/apache/paimon-cpp/pull/286#discussion_r3975030551
##########
include/paimon/reader/file_batch_reader.h:
##########
@@ -63,6 +63,23 @@ class PAIMON_EXPORT FileBatchReader : public BatchReader {
/// Get whether or not support read precisely while bitmap pushed down.
virtual bool SupportPreciseBitmapSelection() const = 0;
+
+ /// Starts whatever background work this reader would otherwise start on
its first read, so a
+ /// caller that knows this reader is next can pay that startup while still
consuming the
+ /// previous one.
+ ///
+ /// This is an optional hint and never changes what the reader returns:
ordering, filtering and
+ /// metrics are the same with or without it. A reader with nothing to
start, or one that is not
+ /// yet ready to start it, does nothing. Calling it before the reader is
configured (for example
+ /// before `SetReadSchema()`), or after `Close()`, is such a no-op.
+ ///
+ /// It reports no error on purpose: the caller may warm up a reader it
never ends up reading,
+ /// and a hint about a file nobody reads must not fail the read in
progress. An implementation
+ /// that cannot start its work leaves it to be started by the first read,
which reports the
+ /// failure itself.
+ /// @warning The call starts background work owned by this reader, so it
must be made from the
+ /// same thread that reads this reader, and not concurrently with any
other call on it.
Review Comment:
Good catch — that wording described one implementation's behavior as if it
were the base-class contract. Plugins are free to define what Warmup() starts,
including doing nothing at all.
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