2010YOUY01 opened a new pull request, #21742:
URL: https://github.com/apache/datafusion/pull/21742
## Which issue does this PR close?
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- Closes #.
## Rationale for this change
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### Background
https://github.com/apache/datafusion/pull/21448 introduced memory-limited
execution for NLJ (thanks to @viirya).
The idea is:
1. Load the build (left) side of the NLJ until the memory limit is reached.
2. Probe the right side and complete the join for the current buffered
build-side chunk.
3. Load the next chunk of the build side and repeat the right-side scan
until all data is processed.
To support repeated probing of the right side, input batches are spilled to
disk during the first pass. In subsequent passes, input is read directly from
the spill. This avoids re-evaluating potentially expensive pipelines (e.g.,
Parquet decoding + filtering), making repeated probes both memory-efficient and
fast.
### This PR
This PR extracts the spill-backed replayable stream into a separate module
to simplify the NLJ implementation.
Although the lines of code increase, the new module provides a clearer
interface and I think it's easier to maintain.
Additionally, this utility may be useful elsewhere. I have seen a similar
pattern in SedonaDB for memory-limited spatial joins.
## What changes are included in this PR?
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- Introducing `ReplayableStreamSource` for the above purpose
- Refactor NLJ logic with `ReplayableStreamSource`
## Are these changes tested?
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UTs, also covered by existing memory-limited NLJ test
## Are there any user-facing changes?
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No
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