Ryan Malloy
92c4fdbcbf
Cursor.execute now branches on DESCRIBE response's nfields:
- nfields > 0 → SELECT path (cursor lifecycle: CURNAME+NFETCH+...)
- nfields == 0 → DDL/DML path (just SQ_EXECUTE then SQ_RELEASE)
Examples that work end-to-end against the dev container:
cur.execute('CREATE TEMP TABLE t (id INTEGER, name VARCHAR(50))')
cur.execute("INSERT INTO t VALUES (1, 'hello')") # rowcount=1
cur.execute("UPDATE t SET name = 'new' WHERE id = 1")
cur.execute('DELETE FROM t WHERE id = 1')
Plus full mix: CREATE → 5 INSERTs → SELECT WHERE → DELETE WHERE → SELECT
(see tests/test_dml.py::test_full_dml_cycle_in_one_connection).
Three protocol findings during this push, documented in DECISION_LOG.md:
1. SQ_INSERTDONE (=94) is METADATA, not execution. It arrives in BOTH
the DESCRIBE response (PREPARE phase) AND the EXECUTE response for
literal-value INSERTs. The PREPARE-phase SQ_INSERTDONE carries the
serial values that WILL be assigned IF you execute. The EXECUTE-
phase SQ_INSERTDONE confirms execution. My initial assumption was
"PREPARE-phase INSERTDONE means already-executed" — wrong. Skipping
SQ_EXECUTE made the row not persist (SELECT returned []). Lesson:
optimization-looking responses may not be what they look like —
always verify with a follow-up SELECT.
2. SQ_INSERTDONE wire format: 18 bytes (10 byte longint serial8 + 8
byte bigint bigserial). Per IfxSqli.receiveInsertDone line 2347.
We read-and-discard for now; Phase 5+ surfaces as Cursor.lastrowid.
3. Transactions: commit() and rollback() are 2-byte messages.
SQ_CMMTWORK=19 + SQ_EOT for commit; SQ_RBWORK=20 + SQ_EOT for
rollback. Server responds with SQ_DONE+SQ_EOT in logged databases,
or SQ_ERR sqlcode=-255 ("Not in transaction") in unlogged databases
like sysmaster. Wire machinery is implemented; full transaction
testing needs a logged DB (use ``stores_demo`` from the dev image).
Module changes:
src/informix_db/cursors.py:
- execute() branches on nfields (SELECT path vs DDL/DML path)
- new _execute_dml() does just EXECUTE + RELEASE
- new _build_execute_pdu() emits the 8-byte SQ_ID(EXECUTE)+EOT
- _read_describe_response() and _drain_to_eot() handle SQ_INSERTDONE
src/informix_db/connections.py:
- commit() / rollback() now functional — send the SQ_CMMTWORK /
SQ_RBWORK PDU and drain the response
Tests: 40 unit + 24 integration (6 new DML tests) = 64 total, all
green, ruff clean. New tests cover:
- CREATE TEMP TABLE
- INSERT (rowcount=1, persists, SELECT shows it)
- UPDATE WHERE (specific row changed)
- DELETE WHERE (specific row removed)
- Full mixed cycle (CREATE + 5 INSERTs + SELECT + DELETE + SELECT)
- commit() in unlogged DB raises OperationalError sqlcode=-255
Captured wire artifacts kept for future debugging:
docs/CAPTURES/16-py-insert-literal.socat.log
docs/CAPTURES/17-py-insert-select.socat.log
232 lines
16 KiB
Markdown
232 lines
16 KiB
Markdown
# Decision Log
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Running rationale for protocol, auth, type, and architecture decisions made during the project. New decisions append; old ones are *amended* (with date) rather than overwritten.
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Format: every decision has a date, a status (`active` / `superseded` / `revisited`), the chosen path, the discarded alternatives, and the *why*.
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---
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## 2026-05-02 — Project goal & off-ramp
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**Status**: active
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**Decision**: Build a pure-Python implementation of the SQLI wire protocol. No IBM Client SDK. No JVM. No native libraries.
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**Off-ramp** (chosen by user during planning): if Phase 0 reveals the protocol is intractable in pure Python — e.g., mandatory undocumented crypto in the handshake — narrow scope (lock to one server version, drop async, drop prepared statements if needed) and stay pure-Python. Do **not** fall back to JPype/JDBC; that defeats the project's purpose.
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**Why**: The "no SDK / no JVM" goal is what makes this driver valuable. A JPype fallback would ship something that works but solves nothing the existing JDBC-via-JPype solution doesn't already solve.
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---
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## 2026-05-02 — Package name
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**Status**: active
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**Decision**: `informix-db`
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**Discarded**: `informixdb-pure` (longer), `ifxsqli` (less discoverable), `pyifx` (obscure)
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**PyPI availability**: confirmed available 2026-05-02 (HTTP 404 on `/pypi/informix-db/json`). The legacy `informixdb` is taken (HTTP 200), `informix` is also free (404) but too generic.
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**Why**: Discoverability balanced with brevity. Anyone searching PyPI for "informix" finds it; the hyphen distinguishes it from the legacy C-extension wrapper.
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---
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## 2026-05-02 — License
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**Status**: active
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**Decision**: MIT
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**Discarded**: Apache-2.0 (more defensive but less common in Python ecosystem), BSD-3-Clause
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**Why**: Simplest, most permissive, ecosystem-standard for Python libraries.
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---
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## 2026-05-02 — Sync first; async deferred
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**Status**: active
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**Decision**: Build a sync, blocking-socket implementation. Async lands in Phase 6+ as a separate `informix_db.aio` subpackage following asyncpg's I/O-agnostic-protocol pattern.
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**Why**: Wire protocols are hard enough; debugging protocol bugs through asyncio plumbing is two layers of indirection too many. Sync-first means we can test against blocking sockets, prove correctness, then mechanically swap the I/O layer.
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---
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## 2026-05-02 — Test target
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**Status**: active
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**Decision**: `icr.io/informix/informix-developer-database` (the Developer Edition image, now maintained by HCL Software since the 2017 IBM→HCL transfer of Informix), port 9088 (native SQLI).
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**Pinned digest** (captured 2026-05-02 from `docker pull`):
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`sha256:8202d69ba5674df4b13140d5121dd11b7b26b28dc60119b7e8f87e533e538ba1`
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**On-disk footprint**: 2.23 GB unpacked / 665 MB compressed.
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**Default credentials** (from container startup logs, accept-license run):
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- OS/DB user: `informix`
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- Password: `in4mix`
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- HQ admin password: `Passw0rd` (don't need this)
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- DBA user/password: empty
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- DBSERVERNAME: defaults to `informix` (same as the user)
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- TLS_CONNECTIONS: OFF (plain auth on port 9088)
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- Always-present databases: `sysmaster`, `sysuser` (built during init)
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**Container startup**: `docker run -d --name ifx --privileged -p 9088:9088 -e LICENSE=accept -e SIZE=small icr.io/informix/informix-developer-database@sha256:8202d69b...`
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**Why**: Free, official, no license click-through, supports plain-password auth out of the box. The digest is locked from Phase 0 onward — `:latest` is the canonical source of flaky integration suites in DB-driver projects, so all `docker-compose.yml` files reference the digest, never the tag.
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---
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## 2026-05-02 — Phase 0 is a gate, not a step
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**Status**: active
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**Decision**: No library code is written until `PROTOCOL_NOTES.md` meets all four exit criteria:
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1. Login byte layout documented end-to-end
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2. Message-type tags identified for login/execute/row/end-of-result/error/disconnect
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3. `SELECT 1` round-trip fully labeled
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4. JDBC source and packet capture corroborate on login + execute paths
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If exit criteria can't be met within bounded effort, invoke the off-ramp.
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**Why**: Most greenfield projects fail by writing code before they understand the problem. This project has an undocumented wire protocol as its central unknown. Gating on Phase 0 means a failed spike still produces a publicly valuable artifact (`PROTOCOL_NOTES.md`) instead of a half-built driver.
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---
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## 2026-05-02 — Phase 1 architecture decisions (locked at start of Phase 1)
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> These are pre-decided so paramstyle/Python-floor/autocommit don't churn later. Recorded here so Phase 1 doesn't relitigate them.
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- **`paramstyle = "numeric"`** (`:1`, `:2`, …). Matches Informix ESQL/C convention.
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- **Python ≥ 3.10**. Gives us `match`, modern type hints, `tomllib`.
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- **`autocommit` defaults to off**. PEP 249 implicit semantics; opt-in via `connect(autocommit=True)`.
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- **Author**: Ryan Malloy `<ryan@supported.systems>` (per global pyproject.toml convention).
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- **Versioning**: CalVer `YYYY.MM.DD` (`2026.05.02` initial); same-day fixes use PEP 440 post-release `2026.05.02.1`, `.2`, etc.
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---
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## 2026-05-02 — DATE pulled forward to MVP
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**Status**: active
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**Decision**: DATE is included in the Phase 2 MVP type set, alongside SMALLINT/INTEGER/BIGINT/FLOAT/CHAR/VARCHAR/BOOLEAN.
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**Discarded**: leaving DATE in the "medium" / Phase 6 bucket.
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**Why**: Almost no real Informix database is DATE-free. The encoding is trivial once the type code is known (4-byte day count from the Informix epoch 1899-12-31). Cheap to include; expensive to leave out.
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DATETIME / INTERVAL / DECIMAL / NUMERIC / MONEY remain in Phase 6+ — their encodings (qualifier-byte precision, BCD-style packed decimal) are non-trivial.
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---
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## 2026-05-02 — `CLAUDE.md` excluded from git and sdist
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**Status**: active
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**Decision**: `.gitignore` excludes `CLAUDE.md`. Once `pyproject.toml` exists, `[tool.hatch.build.targets.sdist].exclude` will also list `CLAUDE.md`.
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**Why**: `CLAUDE.md` contains the user's email and operator-private context. Per global convention, only commit `CLAUDE.md` to private repos. This project is destined for PyPI / public Git.
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---
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## 2026-05-02 — JDBC reference: `ifxjdbc.jar` 4.50.JC10
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**Status**: active
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**Decision**: Use the user-provided `ifxjdbc.jar` from `/home/rpm/bingham/rtmt/lib/` as the JDBC reference, working copy at `build/ifxjdbc.jar`.
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**JAR identity**: `Implementation-Version: 4.50.10-SNAPSHOT`, build 146, dated 2023-03-07. Printable version string: `4.50.JC10`. SHA256 `dc5622cb4e95678d15836b684b6ef1783d37bc0cdd2725208577fc300df4e5f1`.
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**Discarded**: Maven Central `com.ibm.informix:jdbc:4.50.4.1` (not downloaded — the local copy is newer).
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**Why**: A newer reference is strictly better — the wire protocol is backwards-compatible, so anything `4.50.JC10` knows how to send/receive will be accepted by older servers. Avoids the Maven download.
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---
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## 2026-05-02 — Decompiler: CFR 0.152
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**Status**: active
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**Decision**: Use CFR 0.152 (https://github.com/leibnitz27/cfr) as the JDBC decompiler. Cached at `build/tools/cfr.jar`.
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**Discarded**: Procyon, Fernflower, Ghidra (Ghidra MCP port pool was exhausted; CFR alone proved sufficient).
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**Why**: CFR produces the most readable Java for modern bytecode, ships as a single fat JAR, has no install step. Decompiles 478 .java files in seconds.
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---
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## 2026-05-02 — Confirmed: CSM is dead in modern Informix
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**Status**: active
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**Decision**: Do NOT plan for CSM (Communications Support Module) support. Ever.
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**Evidence**: `com.informix.asf.Connection.getOptProperties()` (decompiled) literally throws: `"CSM Encryption is no longer supported"` if `SECURITY` or `CSM` opt-prop is set.
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**Why**: This used to be the supplied-encryption-plugin layer. IBM removed it; modern Informix uses TLS/SSL exclusively. Removes CSM from every phase plan.
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---
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## 2026-05-02 — Wire framing primitives confirmed (from JDBC)
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**Status**: active (pending PCAP corroboration)
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**Decision**: Adopt these wire-framing primitives in `_protocol.py` from day one:
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- All multi-byte integers are **big-endian** (network byte order)
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- SmallInt = 2 bytes, Int = 4 bytes, BigInt = 8 bytes, Real = 4 bytes IEEE 754, Double = 8 bytes IEEE 754
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- Variable-length payloads (string, decimal, datetime, interval, BLOB): `[short length][bytes][optional 0x00 pad if length is odd]` — **the 16-bit alignment requirement is mandatory; missing it desynchronizes the parser**
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- Strings emitted as `[short len+1][bytes][0x00 nul terminator]` (the +1 is the trailing nul)
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- Post-login messages have NO header: each is `[short messageType][payload]` and the next message begins immediately after the previous one's payload ends
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- Login PDU has its own SLheader (6 bytes) + PFheader structure
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**Source**: `com.informix.lang.JavaToIfxType` (encoders), `com.informix.asf.IfxDataInputStream`/`IfxDataOutputStream` (framing), `com.informix.asf.Connection` (login PDU). Documented byte-by-byte in `PROTOCOL_NOTES.md`.
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---
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## 2026-05-02 — Plain-password auth: no challenge-response round trip
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**Status**: active
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**Decision**: For MVP, treat plain-password auth as a single round trip: client sends one binary login PDU containing the password inline; server replies with one PDU containing version + capabilities or an error block.
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**Why**: `Connection.encodeAscBinary()` writes the password as a length-prefixed string within the login PDU body. There is no separate auth phase, no salt, no hashing, no `SQ_CHALLENGE`/`SQ_RESPONSE` exchange. Those constants (129/130) are reserved for PAM and other interactive auth methods, used AFTER the binary login PDU when the server initiates them.
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---
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## 2026-05-02 — Capability ints: corrected after PDU diff caught misread
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**Status**: active (corrects an earlier same-day entry)
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**Decision**: Send `Cap_1 = 0x0000013c, Cap_2 = 0, Cap_3 = 0` in the binary login PDU. These are the values IBM's JDBC driver sends; the server echoes them back identically.
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**Why this is a correction**: An earlier read of the wire bytes (before we wrote the byte-for-byte PDU diff) decoded the capability section as `Cap_1=1, Cap_2=0x3c000000, Cap_3=0`. That was a misalignment — the `0x3c` byte interpreted as `Cap_2`'s high byte was actually `Cap_1`'s low byte. Real layout: a single int `0x0000013c` = `(capability_class << 8) | PF_PROT_SQLI_0600 (60 = 0x3c)`.
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**How we caught it**: `tests/test_pdu_match.py` — captures our generated PDU via a monkey-patched socket and asserts byte-for-byte equality against `docs/CAPTURES/01-connect-only.socat.log` for offsets 2..280 (the structural prefix). The connection still worked with the wrong values because the dev image is permissive, but the PDU was structurally non-identical. **Server-accepts ≠ structurally-correct.**
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**Methodology takeaway**: For wire-protocol implementations, always diff against the reference vendor's PDU bytes, not just "it connected." Permissive servers mask real bugs.
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---
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## 2026-05-04 — VARCHAR row decoding: three byte-level discoveries
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**Status**: active
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**Decision**: ``parse_tuple_payload`` now handles VARCHAR/NCHAR/NVCHAR with a single-byte length prefix; SQ_TUPLE payloads are padded to even byte alignment; the trailing reserved field in CURNAME+NFETCH is a SHORT not an INT.
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**Why this is three findings**: each one was caught by a different debugging technique:
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1. **CURNAME+NFETCH PDU off by 2 bytes**: my reserved trailing field was `write_int(0)` (4 bytes); JDBC's reference is `write_short(0)` (2 bytes). Caught by capturing both PDUs under socat and byte-diffing — our 44-byte vs JDBC's 42-byte. The server happened to accept the longer version for INT-only SELECTs (silently treating the extra zeros as padding) but rejected it for VARCHAR queries. Lesson: **server tolerance varies by query type — always match JDBC byte-for-byte**.
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2. **SQ_TUPLE payload pads to even alignment**: when `size` is odd, an extra 0x00 byte follows the payload before the next tag. Found in `docs/CAPTURES/15-py-varchar-fixed.socat.log` — an 11-byte "syscolumns" VARCHAR payload had a trailing `0x00` that JDBC's `IfxRowColumn.readTuple` consumes silently. We weren't doing this, so the parser desynced for any odd-length variable-width row. **Even-byte alignment is a wire-protocol-wide invariant — every variable-length payload pads.**
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3. **VARCHAR in tuple uses 1-byte length prefix, NOT 2**: per the on-wire encoding (verified empirically in capture 15), VARCHAR values in row data are `[byte length][bytes]` — single-byte prefix, max 255 chars. NCHAR and NVCHAR follow the same pattern. (CHAR is fixed-width per encoded_length, no length prefix at all.) LVARCHAR uses a 4-byte int prefix for values >255 bytes.
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**How to apply**: when adding new variable-width type decoders, capture a tuple under socat first to see the exact framing — don't infer from the column descriptor's `encoded_length`, which is the MAX storage, not the wire format. The wire format may differ by orders of magnitude (1-byte prefix vs encoded_length=128 for VARCHAR).
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---
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## 2026-05-04 — DML / DDL execution path: SQ_PREPARE + SQ_EXECUTE + SQ_RELEASE
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**Status**: active
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**Decision**: For statements that don't return rows (CREATE, INSERT, UPDATE, DELETE, DROP), Cursor.execute branches on ``nfields == 0`` in the DESCRIBE response. SELECT path is the cursor lifecycle (CURNAME+NFETCH+...); DDL/DML path is just SQ_EXECUTE then SQ_RELEASE.
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**Why**: JDBC uses SQ_PREPARE for everything; for non-SELECT it just doesn't open a cursor. Per IfxSqli.sendExecute (line 1075): non-prepared-statement execute is a bare ``[short SQ_ID=4][int SQ_EXECUTE=7][short SQ_EOT]`` (8 bytes).
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---
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## 2026-05-04 — SQ_INSERTDONE (=94) is execution metadata, NOT execution
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**Status**: active
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**Decision**: SQ_INSERTDONE arrives in BOTH the DESCRIBE response (PREPARE phase) AND the EXECUTE response for literal-value INSERTs. It carries the auto-generated serial values that WILL be / WERE inserted. Don't interpret SQ_INSERTDONE in the DESCRIBE response as "row was inserted" — it's just metadata. Always send SQ_EXECUTE.
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**Why this was a debugging trap**: when I first saw SQ_INSERTDONE in the PREPARE response for ``INSERT INTO t1 VALUES (1, 'hello')``, I assumed Informix optimizes literal INSERTs by executing during PREPARE and added a "skip SQ_EXECUTE" branch. Result: SELECT returned 0 rows. The data wasn't actually inserted; the SQ_INSERTDONE in PREPARE was just "here are the serials that WILL be assigned when you execute". After reverting to "always send SQ_EXECUTE", the row persists. Lesson: optimization-looking responses may not be what they look like — always verify with a follow-up SELECT.
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---
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## 2026-05-04 — SQ_INSERTDONE wire format
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**Status**: active
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**Decision**: Per IfxSqli.receiveInsertDone (line 2347), the SQ_INSERTDONE payload is 18 bytes for modern (bigint-supported) servers:
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- 10 bytes: serial8 inserted (Informix's variable-numeric LONGINT encoding)
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- 8 bytes: bigserial inserted (regular 64-bit long, big-endian)
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For now we read-and-discard. Phase 5+ will surface these as ``Cursor.lastrowid`` / similar.
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---
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## 2026-05-04 — Transactions: commit/rollback are 2-byte messages
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**Status**: active
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**Decision**: ``Connection.commit()`` sends ``[short SQ_CMMTWORK=19][short SQ_EOT=12]`` (4 bytes). ``Connection.rollback()`` sends ``[short SQ_RBWORK=20][short SQ_EOT=12]``. Server responds with SQ_DONE+SQ_EOT (in logged databases) or SQ_ERR sqlcode=-255 ("Not in transaction") in unlogged databases like sysmaster.
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**How to apply**: integration tests for transactions need a LOGGED database. The Informix Developer Edition image ships with ``stores_demo`` (logged) — point integration tests at that for commit/rollback verification.
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---
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## (template — copy below this line for new entries)
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```
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## YYYY-MM-DD — <one-line decision title>
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**Status**: active | superseded | revisited
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**Decision**: <chosen path>
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**Discarded**: <alternatives, briefly>
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**Why**: <rationale>
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```
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