fix(workflow-operator): Text Input operator using offset with an empty limit emits no rows

[eugenegujing]

What changes were proposed in this PR?

TextInputSourceOpExec computed its line window as slice(offset, offset + limit.getOrElse(Int.MaxValue)). With an Offset set and the Limit left empty, the addition overflows Int to a negative bound, which Scala 2.13's Iterator.slice clamps to 0 and then returns an empty iterator — so the operator silently emitted zero rows while the workflow reported success. Any Offset ≥ 1 with an empty Limit is affected, and an explicit large Limit (e.g. Int.MaxValue) overflows the same way. This contradicts the Limit property's own description, "Leave empty to read all lines."

This PR replaces the slice with drop(offset) + take(limit), the same idiom the CSV, Arrow, and JSONL scan sources already use. There is no addition, so nothing can overflow; every configuration that previously worked is unchanged (verified case-by-case, including negative offsets and isSingle attribute types, which keep ignoring offset/limit as documented).

Before the fix (current main) — Offset = 1, Limit left empty, five-line input a b c d e: the result is an empty set even though the workflow completes successfully. Expected: the four rows b, c, d, e.

Control on the same build — Offset = 0, Limit left empty returns all five rows:

Any related issues, documentation, discussions?

Closes #7346.

Same class of defect as #7245 (JSONL File Scan dropping rows when Offset is set), which was fixed by #7247.

How was this PR tested?

TDD: the regression tests were written first and confirmed to fail on the unfixed code — the offset-without-limit case and the offset-with-Int.MaxValue-limit case both produced empty output — then the fix was applied and all tests pass.

Seven new cases were added to TextInputSourceOpDescSpec (the spec that already exercises produceTuple()): offset without limit, offset with an Int.MaxValue limit, offset+limit window, limit only, offset at/past the end of the input, negative offset treated as zero, and SINGLE_STRING ignoring offset/limit (documented behavior, pinned).

sbt "WorkflowOperator/testOnly org.apache.texera.amber.operator.source.scan.text.TextInputSourceOpDescSpec"
# 17 tests, all passed (10 pre-existing + 7 new)

sbt "WorkflowOperator/testOnly org.apache.texera.amber.operator.source.scan.*"
# 17 suites, 123 tests, all passed

sbt "WorkflowOperator/scalafixAll --check"
# passed, no lint issues

sbt scalafmtCheckAll
# passed, no mis-formatted files

Also verified manually in the UI with the same two-operator workflow shown in the screenshots above:

Was this PR authored or co-authored using generative AI tooling?

Co-authored by: Claude Code (Claude Fable 5)

[github-actions]

Automated Reviewer Suggestions

Based on the git blame history of the changed files, we recommend the following reviewers:

• Contributors with relevant context: @Yicong-Huang, @aglinxinyuan
  You can notify them by mentioning @Yicong-Huang, @aglinxinyuan in a comment.

[github-actions]

Backport auto-label report

This fix: PR was checked against each actively-supported release branch. release/* labels drive the post-merge backport, so add or remove one to change where this fix lands.

Release branch	Analysis
✅ release/v1.2	Change detected on this branch — label added; this fix is queued to backport here. Requested review from @xuang7.

Auto-label run.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 83.25%. Comparing base (88ca47f) to head (91af32d).
⚠️ Report is 1 commits behind head on main.
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #7347      +/-   ##
============================================
- Coverage     86.24%   83.25%   -3.00%     
- Complexity     4211     4741     +530     
============================================
  Files          1169     1228      +59     
  Lines         46736    51386    +4650     
  Branches       5203     5847     +644     
============================================
+ Hits          40308    42780    +2472     
- Misses         4691     6715    +2024     
- Partials       1737     1891     +154     

Flag	Coverage Δ		*Carryforward flag
access-control-service	71.10% <ø> (+1.10%)	⬆️
agent-service	86.87% <ø> (ø)		Carriedforward from aa791a4
amber	76.78% <100.00%> (-5.10%)	⬇️
computing-unit-managing-service	35.12% <ø> (-15.61%)	⬇️
config-service	64.02% <ø> (-1.96%)	⬇️
file-service	64.13% <ø> (-4.92%)	⬇️
frontend	88.91% <ø> (ø)		Carriedforward from aa791a4
notebook-migration-service	78.89% <ø> (ø)
pyamber	97.55% <ø> (ø)		Carriedforward from aa791a4
workflow-compiling-service	51.78% <ø> (+25.46%)	⬆️

*This pull request uses carry forward flags. Click here to find out more.

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[github-actions]

⚠️ Benchmark changes need a look

🟢 0 better · 🔴 6 worse · ⚪ 9 noise (<±5%) · 0 without baseline

Compared against main 88ca47f benchmarked on this same runner, so the delta is largely free of cross-runner hardware noise. The "7d avg" column still reflects the gh-pages dashboard. Treat <±5% as noise unless repeated.

Dashboard · Run

	config	throughput	MB/s	latency	max Δ latest / 7d
🔴	bs=10 sw=10 sl=64	367	0.224	24,564/44,465/44,465 us	🔴 +41.0% / 🔴 +171.3%
⚪	bs=100 sw=10 sl=64	793	0.484	124,540/141,683/141,683 us	⚪ within ±5% / 🔴 +25.9%
🔴	bs=1000 sw=10 sl=64	907	0.553	1,088,989/1,298,526/1,298,526 us	🔴 +6.0% / 🔴 +20.7%

Baseline details

Latest main 88ca47f from same runner

config	metric	PR	latest main	7d avg	Δ latest	Δ 7d
bs=10 sw=10 sl=64	throughput	367 tuples/sec	423 tuples/sec	743.73 tuples/sec	-13.2%	-50.7%
bs=10 sw=10 sl=64	MB/s	0.224 MB/s	0.258 MB/s	0.454 MB/s	-13.2%	-50.7%
bs=10 sw=10 sl=64	p50	24,564 us	24,064 us	13,130 us	+2.1%	+87.1%
bs=10 sw=10 sl=64	p95	44,465 us	31,537 us	16,391 us	+41.0%	+171.3%
bs=10 sw=10 sl=64	p99	44,465 us	31,537 us	19,408 us	+41.0%	+129.1%
bs=100 sw=10 sl=64	throughput	793 tuples/sec	826 tuples/sec	944.04 tuples/sec	-4.0%	-16.0%
bs=100 sw=10 sl=64	MB/s	0.484 MB/s	0.504 MB/s	0.576 MB/s	-4.0%	-16.0%
bs=100 sw=10 sl=64	p50	124,540 us	120,038 us	105,853 us	+3.8%	+17.7%
bs=100 sw=10 sl=64	p95	141,683 us	148,526 us	112,493 us	-4.6%	+25.9%
bs=100 sw=10 sl=64	p99	141,683 us	148,526 us	122,200 us	-4.6%	+15.9%
bs=1000 sw=10 sl=64	throughput	907 tuples/sec	927 tuples/sec	972.22 tuples/sec	-2.2%	-6.7%
bs=1000 sw=10 sl=64	MB/s	0.553 MB/s	0.566 MB/s	0.593 MB/s	-2.3%	-6.8%
bs=1000 sw=10 sl=64	p50	1,088,989 us	1,072,675 us	1,033,856 us	+1.5%	+5.3%
bs=1000 sw=10 sl=64	p95	1,298,526 us	1,225,461 us	1,076,083 us	+6.0%	+20.7%
bs=1000 sw=10 sl=64	p99	1,298,526 us	1,225,461 us	1,107,701 us	+6.0%	+17.2%

Raw CSV

config_idx,batch_size,schema_width,string_len,num_batches,total_ms,total_tuples,total_bytes,tuples_per_sec,mb_per_sec,lat_p50_us,lat_p95_us,lat_p99_us
0,10,10,64,20,544.97,200,128000,367,0.224,24564.02,44464.60,44464.60
1,100,10,64,20,2523.41,2000,1280000,793,0.484,124540.29,141682.77,141682.77
2,1000,10,64,20,22058.75,20000,12800000,907,0.553,1088989.31,1298525.63,1298525.63

[eugenegujing]

/request-review @aglinxinyuan

[chenlica]

@carloea2 Can you review it first?

[carloea2]

Looks good to me.

[github-actions]

Backport PR opened: draft #7495 (#7495) to release/v1.2, assigned to @eugenegujing — needs manual work because the backported tree failed its pre-merge build.