Architecture of a DBMS: the five-box org chart

A database is five cooperating managers, and a storage engine is just one of them. This chapter maps Hellerstein, Stonebraker & Hamilton’s survey — the curriculum’s atlas — onto the topics ahead: read the map chapters this week, then return per-topic as each box gets built. You are NOT reading all ~120 pages now; budget 2 h.

Read NOW (topic 1)

§1 (main components) — the five-box diagram of a DBMS. Memorize it; it’s the table of contents for topics 3–16:

flowchart TB
    CM["Client communications manager<br/>(topic 7: protocol, RESP)"] --> PC["Process manager<br/>(topic 7/9: threads, admission)"]
    PC --> RP["Relational query processor<br/>parse → rewrite → optimize → execute<br/>(topics 10-11)"]
    RP --> TS["Transactional storage manager<br/>access methods + buffer + locks + log<br/>(topics 1-6, 8-9)"]
    TS --> SC["Shared components<br/>catalog, memory allocator, replication<br/>(topics 15, 22)"]

§2 (process models) — process-per-worker vs thread-per-worker vs event/async; where admission control lives. Directly informs the capstone server (M7/M9).
§6 (storage management) — spatial control (why DBs fight the filesystem), buffer pools vs OS page cache, the double-buffering problem. This is the section that justifies this topic’s existence.

Skim NOW, return LATER

Section	Return at
§3 parser/rewriter	topic 10
§4 query processor internals	topics 10–11
§5 transactions, ACID, locking	topics 8–9
§7 shared components (catalog, replication)	topics 15–16

Questions to answer in notes.md

§6 argues the DBMS should bypass OS caching (O_DIRECT). What are the two distinct problems with letting the OS cache pages? (Double buffering; the OS evicts/flushes with zero knowledge of WAL ordering.)
Which of the five §1 boxes does fjall implement? redb? (Neither has a query processor or client manager — “storage engine” ≠ “database”. The capstone builds the other boxes on top, milestone by milestone.)
2007 blind spots: name three things the paper couldn’t see coming. (Candidates: NVMe erasing the seek-time mental model, cloud disaggregation — topic 28, columnar dominance for analytics — topic 12, LSM taking over write paths.)

The one-line takeaway

A database is five cooperating managers, and a storage engine is just one of them — this paper is the org chart for everything the capstone will build.

References

Papers

Hellerstein, Stonebraker, Hamilton — “Architecture of a Database System” (Foundations and Trends in Databases, 2007) — PDF — read §1–2 + §6 now (2 h); §3–§5 and §7 are reference material to return to per the table above

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