CUBRID OOS (Out-of-row Overflow Storage)

Knowledge base for the CUBRID OOS project — separating large variable-length columns from heap records into dedicated OOS files to reduce unnecessary disk I/O.

Core Documents

OOS Presentation — Architecture overview, record format, CRUD flows, MVCC integration (Marp slides)
OOS Test Scenarios — ACID, crash recovery, MVCC, replication test cases using VARBIT patterns
OOS Schedule — M2 milestone timeline (3/10–4/17), task assignments, weekly plan
OOS TODO — Known bugs, open issues (CBRD-26458 unloaddb perf, CBRD-26516 redundant oos_read)

Reference (CUBRID Internals)

Heap Bestspace Algorithm — How CUBRID picks which heap page to insert into
Page Buffer Analysis (EN) — page_buffer.c code analysis report
Page Buffer Analysis (KO) — 페이지 버퍼 모듈 분석 보고서 (한국어)

Quick Reference

Concept	Detail
OOS trigger	record > `DB_PAGESIZE/8` (2KB) AND column > 512B
OOS file type	`FILE_OOS`, one per heap file (1:1)
OOS pointer	8-byte OOS OID (volid, pageid, slotid) in variable area
MVCC flags	`OR_MVCC_FLAG_HAS_OOS` (bit 3), `OR_VAR_BIT_OOS` (bit 0)
Key source	`heap_file.c`, `oos_file.cpp`, `object_representation.h`

JIRA

CBRD-26517 — Main OOS tracking issue
CBRD-26458 — unloaddb heap_next performance regression
CBRD-26516 — UPDATE redundant oos_read calls