Cursor class scaffolded with full PEP 249 surface:
src/informix_db/cursors.py — Cursor with execute, fetchone, fetchmany,
fetchall, description, rowcount, arraysize, close, iterator,
context manager. Sends SQ_COMMAND chains for parameterless SQL
(Phase 4 adds SQ_BIND/SQ_EXECUTE for params).
src/informix_db/_resultset.py — ColumnInfo, parse_describe,
parse_tuple_payload. Best-effort SQ_DESCRIBE parser; refines in
Phase 2.1.
src/informix_db/connections.py — Connection.cursor() now returns a
real Cursor; new _send_pdu() lets Cursor share the connection's
socket without violating encapsulation.
Protocol findings landed in PROTOCOL_NOTES.md §6:
§6a — SQ_PREPARE format with named tags (the "trailing 22, 49"
are SQ_NDESCRIBE and SQ_WANTDONE chained into the same PDU).
Confirmed against IfxSqli.sendPrepare line 1062.
§6c — Server requires post-login init sequence (SQ_PROTOCOLS →
SQ_INFO → SQ_ID(env vars) → SQ_DBOPEN) BEFORE any PREPARE works.
Discovered the hard way: PREPARE without this sequence gets no
response; SQ_DBOPEN without SQ_PROTOCOLS gets sqlcode=-759
("Database not available"). The login PDU's database field is
a hint, not an open.
§6e — SQ_TUPLE corrected: [short warn][int size][bytes payload]
(not [int 0][short payloadLen] as earlier draft claimed).
Two more constants added to _messages.MessageType:
SQ_NDESCRIBE = 22, SQ_WANTDONE = 49
Tests: 40 unit + 7 integration (added 2 new — cursor() returns a
Cursor, parameter binding raises NotSupportedError). All green, ruff
clean. Removed obsolete "cursor() raises NotImplementedError" test.
What works end-to-end now: connect, cursor(), close, parameter-attempt
gating. What doesn't yet: cursor.execute("SELECT 1") — server requires
the post-login init sequence we don't yet send.
Discovered captures (kept for next session's analysis):
docs/CAPTURES/06-py-select1-attempt.socat.log
docs/CAPTURES/07-py-replay-jdbc-prepare.socat.log
docs/CAPTURES/08-py-with-dbopen.socat.log
docs/CAPTURES/09-py-full-replay.socat.log
Three new tasks created tracking the remaining Phase 2 blockers:
post-login init sequence, proper SQ_DESCRIBE parser, SQ_ID action
vocabulary helpers.
Polish item #1: byte-for-byte regression test that asserts our
generated login PDU is structurally identical to JDBC's reference
captured in docs/CAPTURES/01-connect-only.socat.log.
The test (tests/test_pdu_match.py) immediately caught a real bug:
the capability section was misread during Phase 0 byte-decoding.
Earlier text claimed Cap_1=1, Cap_2=0x3c000000, Cap_3=0 — actually:
Cap_1 = 0x0000013c (= (capability_class << 8) | protocol_version
where protocol_version = 0x3c = PF_PROT_SQLI_0600)
Cap_2 = 0
Cap_3 = 0
The misalignment was: the 0x3c byte I attributed to Cap_2's high
byte was actually Cap_1's low byte. The dev-image server is
permissive enough to accept arbitrary capability values, so the
connection succeeded even with the wrong bytes — but the PDU wasn't
structurally identical to JDBC's reference. SERVER-ACCEPTS ≠
STRUCTURALLY-CORRECT. This is exactly why the byte-for-byte diff
was the right polish item; "it connects" was a false ceiling.
After fix:
- 6 PDU-match tests assert byte-for-byte equality at offsets 2..280
(the structural prefix: SLheader sans length, all login markers,
capability ints, username, password, protocol IDs, env vars).
- Bytes 280+ legitimately differ per process (PID, TID, hostname,
cwd, AppName) — those are NOT asserted.
- Length field (offsets 0..1) also legitimately differs because our
PDU has shorter env list and AppName.
- Test uses monkey-patched IfxSocket so no network is needed.
Polish item #2: Makefile per global CLAUDE.md convention. Targets:
install, lint, format, test, test-integration, test-all, test-pdu,
ifx-up/down/logs/shell/status, capture (re-run JDBC scenarios under
socat), clean. `make` (no target) prints help.
Doc updates:
- PROTOCOL_NOTES.md §12: corrected capability section with the
actual values and an explanation of the methodology lesson
- DECISION_LOG.md: new entry recording the correction with a
pointer to the regression test and the takeaway
Side artifacts:
- docs/CAPTURES/03-py-connect-only.socat.log
- docs/CAPTURES/04-py-no-database.socat.log
- docs/CAPTURES/05-py-fixed-caps.socat.log
Test counts: 40 unit + 6 integration = 46 total, all green, ruff clean.
The user's global ~/.gitignore_global excludes *.log universally, which
silently dropped our docs/CAPTURES/*.socat.log files from the previous
Phase 0 commit. Add explicit negation rules in the project .gitignore
so the spike capture deliverables are tracked.
Captured under socat MITM relay (host:9090 → container:9088, hex-dump
both directions), driven by tests/reference/RefClient.java:
- 01-connect-only.socat.log: bare login + disconnect (~1.7 KB)
- 02-select-1.socat.log: SELECT 1 round-trip (~6.7 KB)
- 02-dml-cycle.socat.log: CREATE TEMP + INSERT + SELECT (~9.9 KB)
These are referenced from PROTOCOL_NOTES.md §12 as the canonical
ground-truth for the wire-format claims.
