[BugFix] Guard against iterator UB in get_column_values when rssid not found (backport #69617)

[mergify]

Why I'm doing:

When the PrimaryIndex contains stale entries pointing to rowsets that have been compacted away, TabletUpdates::get_column_values crashes with SIGSEGV. The root cause is that upper_bound(rssid) returns begin() when the requested rssid is smaller than all keys in rssid_to_rowsets, and then --iter on begin() is undefined behavior. In practice this causes the iterator to point to the map's sentinel node, leading to dereference of corrupted memory.

Core dump analysis confirmed:

• rssid = 432750 from PrimaryIndex lookup
• rssid_to_rowsets min key = 476512 (old rowsets already compacted)
• --begin() UB → dereference of corrupted RowsetMetaPB pointer 0x80804509150b1880 → SIGSEGV

What I'm doing:

Add a bounds check before decrementing the upper_bound iterator. When iter == begin(), return InternalError with a descriptive message instead of crashing.

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 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

    ---

    This is an automatic backport of pull request [BugFix] Guard against iterator UB in get_column_values when rssid not found #69617 done by Mergify.

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🕒 Last updated: Mon, 02 Mar 2026 02:51:04 GMT

[mergify]

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