Fix overlap detection with running max#10315
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@dbeck, @svenklemm: please review this pull request.
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Overlap detection compared only against the immediately previous batch's last value. A small intermediate batch (e.g. a 1-row boundary batch) could reset the comparison point and hide overlaps with later batches, requiring multiple compaction passes to converge. Track the running maximum of last values instead, so all overlaps within a segment are detected in a single pass. Uses full-tuple comparison to avoid mixing column values from different batches in multi-column orderby.
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| DROP TABLE metrics_max_batches; | ||
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| -- Test Small intermediate batches must not hide overlaps with later batches. | ||
| CREATE TABLE metrics_running_max (time TIMESTAMPTZ NOT NULL, value float) |
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Let's also test DESC order i.e. for time DESC for example.
Multikey orderby with different key direction would also be interesting to test.
Also, would be interesting to test on compressed hypertable with segmentby.
svenklemm
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Jul 24, 2026
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Overlap detection compared only against the immediately previous batch's last value. A small intermediate batch (e.g. a 1-row boundary batch) could reset the comparison point and hide overlaps with later batches, requiring multiple compaction passes to converge.
Track the running maximum of last values instead, so all overlaps within a segment are detected in a single pass. Uses full-tuple comparison to avoid mixing column values from different batches in multi-column orderby.