[beryllw]

Purpose

Fixes #4656.

Historical primary-key splits write to multiple Paimon partitions and buckets, repeatedly scanning manifests during writer initialization.

Brief change log

Default write.sequence-number-init-mode to snapshot when creating a Paimon primary-key table with historical partition access enabled and automatic compaction disabled. Persist the option so writers and external compactors inherit it, while preserving explicit settings. Log tables and existing Paimon tables are unchanged.

Tests

• Cover creation-time defaults, explicit overrides, sequence-number progression, external compaction, and subsequent updates/deletes.
• Use real catalog/writer paths and capture Paimon scan-completion logs: a historical writer targeting two partitions performs 0 plans with the default optimization, versus 2 with explicit scan or automatic compaction enabled.
• Paimon module verification passed: 217 unit tests and 59 integration tests, plus Spotless and Checkstyle.

API and Format

No API or storage-format changes.

Documentation

Document the creation-time default, Paimon 2.0 requirement, and scan opt-out under historical partition access.

[beryllw]

@luoyuxia cc