Description

Problem

#18249 made aligned MemTable bitmaps lazy, but the write-memory estimator still defensively reserved a bitmap object and bitmap-list reference for every value block. That reservation can make memory accounting larger than the objects that are actually materialized and may reject writes unnecessarily.

A newly extended column also keeps its historical value arrays as null. Therefore, this accounting model should not charge the additional 4-byte object reference for each historical null placeholder; the reference is charged only when the value array is materialized.

Fix

• Remove the unconditional per-block bitmap reservation and account for bitmap references/objects only when they are actually created.
• Track materialized value-array and bitmap costs incrementally in AlignedTVList, with an O(1) getRamSize() for the write path.
• Reconcile aligned TVList RAM after row, rows, and tablet writes, including mixed-alignment rows, multi-device tablets, and sorted TVLists.

The correction is:

actual aligned TVList RAM delta - estimated aligned MemTable increment

A positive correction is reserved in both DataRegionInfo and the MemTable; a negative correction is released from both and refreshes the storage-group status. Chunk metadata and variable-length Binary payload accounting are intentionally unchanged.

Performance

The new performance UT is disabled by default and can be enabled with:

mvn -pl iotdb-core/datanode test \
  -Dtest=AlignedBitmapMemoryAccountingPerformanceTest \
  -Diotdb.aligned.bitmap.accounting.perf.enabled=true

Default benchmark setup: 64 columns, 256 rows per batch, 200 warmups, 2,000 batches per round, and 5 rounds. Reconciliation is repeated internally to avoid Windows CPU timer granularity and then normalized per batch.

The measured reconciliation overhead is therefore negligible for both dense and null-heavy writes.

Verification

• AlignedTVListTest: 15 passed
• TsFileProcessorTest: 20 passed
• Performance UT default-off behavior: 1 skipped as expected
• Performance UT enabled: 1 passed
• IoTDBAlignedTVListLazyAllocationIT: 1 passed on a packaged 1C1D cluster
• Datanode and integration-test Checkstyle: 0 violations
• Spotless and git diff --check: passed

This PR has:

• been self-reviewed.
• added comments explaining the intent of the accounting and reconciliation logic.
• added or updated unit tests to cover the new code paths.
• added/updated an integration test.
• been tested in a test IoTDB cluster.

Key changed/added classes

• AlignedTVList: actual materialized value-array/bitmap RAM tracking and constant-time RAM lookup.
• TsFileProcessor: post-write aligned RAM reconciliation.
• AlignedBitmapMemoryAccountingPerformanceTest: opt-in reconciliation overhead benchmark.