[Enhancement] only read iceberg cache when mv refresh and inesert select stmt

[Wenjun7J]

Why I'm doing:

What I'm doing:

Fixes #issue

What type of PR is this:

• BugFix
• Feature
• Enhancement
• Refactor
• UT
• Doc
• Tool

Does this PR entail a change in behavior?

• Yes, this PR will result in a change in behavior.
• No, this PR will not result in a change in behavior.

If yes, please specify the type of change:

• Interface/UI changes: syntax, type conversion, expression evaluation, display information
• Parameter changes: default values, similar parameters but with different default values
• Policy changes: use new policy to replace old one, functionality automatically enabled
• Feature removed
• Miscellaneous: upgrade & downgrade compatibility, etc.

Checklist:

• I have added test cases for my bug fix or my new feature
• This pr needs user documentation (for new or modified features or behaviors)
  • I have added documentation for my new feature or new function
  • This pr needs auto generate documentation
• This is a backport pr

Bugfix cherry-pick branch check:

• I have checked the version labels which the pr will be auto-backported to the target branch
  • 4.1
  • 4.0
  • 3.5
  • 3.4

[github-actions]

[Java-Extensions Incremental Coverage Report]

✅ pass : 0 / 0 (0%)

[github-actions]

[FE Incremental Coverage Report]

✅ pass : 6 / 6 (100.00%)

file detail

	path	covered_line	new_line	coverage	not_covered_line_detail
🔵	com/starrocks/qe/StmtExecutor.java	4	4	100.00%	[]
🔵	com/starrocks/qe/ConnectContext.java	2	2	100.00%	[]

[github-actions]

[BE Incremental Coverage Report]

✅ pass : 0 / 0 (0%)

[alvin-celerdata]

@codex review

[chatgpt-codex-connector]

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[chatgpt-codex-connector]

Keep caches attached when only-read mode is set

When onlyReadIcebergCache is true you currently set both caches to null, which makes StarRocksIcebergTableScan.useCache() return false because it checks dataFileCache != null. That means MV refresh / INSERT‑SELECT will bypass existing manifest caches entirely instead of reading from them, and will re-scan manifests every time even if they were already cached. If the intent is “read cache but don’t populate/refresh,” you should keep the caches attached and rely on onlyReadCache (which is already honored in planTaskWithCache) to skip puts; otherwise this change silently disables the cache in exactly the paths it was meant to use.

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