github-actions[bot] commented on code in PR #68610:
URL: https://github.com/apache/doris/pull/68610#discussion_r4132871043
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be/src/exec/scan/scanner.cpp:
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@@ -88,6 +89,38 @@ Status Scanner::init(RuntimeState* state, const
VExprContextSPtrs& conjuncts) {
}
Status Scanner::get_block_after_projects(RuntimeState* state, Block* block,
bool* eos) {
+ RETURN_IF_ERROR(_get_block_after_projects(state, block, eos));
+ // Publish progress to the shared counter so peer scanners can observe it.
Only rows that leave
+ // the scanner are charged: rows still held in _padding_block are not
charged, because once
+ // the counter is exhausted the context may finish without running this
scanner again. The
+ // counter may go negative when several scanners subtract concurrently;
that is harmless
+ // because the operator's reached_limit() makes the final cut.
+ if (_shared_scan_limit && block->rows() > 0) {
+ _shared_scan_limit->fetch_sub(block->rows(),
std::memory_order_acq_rel);
+ *eos = *eos || _shared_scan_limit->load(std::memory_order_acquire) <=
0;
+ }
+ // After the charge above, so peers never see the emitted rows missing
from both counters.
+ _publish_padding_rows();
+ return Status::OK();
+}
+
+void Scanner::_publish_padding_rows() {
+ if (!_shared_scan_limit) {
+ return;
+ }
+ const auto padding_rows = cast_set<int64_t>(_padding_block.rows());
+ _shared_scan_buffered_rows->fetch_add(padding_rows -
_published_padding_rows,
Review Comment:
[P2] Skip zero-delta publication on ordinary LIMIT scans.
`get_block_after_projects()` calls this for every successful block, but the
no-projection path leaves `_padding_block` and `_published_padding_rows` at
zero. `fetch_add(0, acq_rel)` still adds a shared atomic read-modify-write on
every block across parallel scanners, with no value to publish. Skip the RMW
when the padding-row delta is zero, while retaining updates when padding
actually changes.
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