cur.execute("INSERT INTO t VALUES (?, ?, ?)", (42, "hello", 3.14))
cur.execute("INSERT INTO t VALUES (:1, :2)", (99, "world"))
cur.execute("UPDATE t SET name = ? WHERE id = ?", ("new", 2))
cur.execute("DELETE FROM t WHERE id = ?", (5,))
# all work end-to-end against a real Informix server
Two breakthroughs decoded from JDBC:
1. SQ_BIND PDU shape (chained with SQ_EXECUTE in one PDU, no separate
round trip):
[short SQ_ID=4][int SQ_BIND=5][short numparams]
for each param:
[short type][short indicator][short prec_or_encLen]
writePadded(rawbytes)
[short SQ_EXECUTE=7][short SQ_EOT]
2. Strings are sent as CHAR (type=0) not VARCHAR (type=13). The server
handles conversion to the actual column type via internal CIDESCRIBE
— we don't need to do it explicitly.
Per-type encoding (Phase 4 MVP):
int (32-bit) → IDS INT (type=2), prec=0x0a00 (packed width=10/scale=0),
4-byte BE
int (64-bit) → IDS BIGINT (type=52), prec=0x1300, 8-byte BE
str → IDS CHAR (type=0), prec=0, [short len][bytes][pad]
float → IDS FLOAT (type=3), prec=0, 8-byte IEEE 754
bool → IDS BOOL (type=45), prec=0, 1 byte
None → indicator=-1, no data
The integer "precision" field is PACKED — initially looked like a bug
(why would precision be 2560?) until I realized 0x0a00 = (10 << 8) | 0
= packed display-width and scale. Captured this surprise in
DECISION_LOG.md.
Critical fix to execute-path branching: parameterized INSERT also
returns nfields > 0 (server describes the would-be inserted row).
Switched from "branch on nfields" to "branch on SQL keyword" — JDBC
does the same via its IfxStatement / IfxPreparedStatement subclassing.
Numeric paramstyle support: cur.execute("... :1 ...", (val,)) works
by rewriting :N → ? before sending PREPARE. Trivial regex (doesn't
escape strings/comments — Phase 5 can add a proper SQL tokenizer).
Module changes:
src/informix_db/converters.py:
+ encode_param() dispatcher
+ _encode_int / _encode_bigint / _encode_str / _encode_float / _encode_bool
src/informix_db/cursors.py:
+ _build_bind_execute_pdu() — chains SQ_BIND + SQ_EXECUTE in one PDU
+ _execute_dml_with_params() — sends bind PDU, drains, releases
+ execute() now accepts parameters; rewrites :N → ?; branches by
SQL keyword (SELECT vs DML)
+ _NUMERIC_PLACEHOLDER_RE for paramstyle="numeric" support
Tests: 40 unit + 32 integration (8 new parameter tests + 1 updated
smoke) = 72 total, all green, ruff clean. New tests cover:
- INSERT with ? params
- INSERT with :N params
- INT + FLOAT + str round trip via INSERT then SELECT
- UPDATE with params in SET and WHERE
- DELETE with parameter in WHERE
- Unsupported param type (bytes) raises NotImplementedError
- Parameterized SELECT raises NotSupportedError (Phase 4.x)
- Dict/named params raise NotSupportedError
Known gaps (Phase 4.x / Phase 5):
- Parameterized SELECT (needs SQ_BIND before CURNAME+NFETCH)
- NULL row decoding for VARCHAR (currently surfaces empty string)
- Proper SQL tokenizer (so :N inside string literals is preserved)
- bytes/datetime/Decimal parameter types
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
