Now you can pass Python datetime/date/Decimal values directly:
cur.execute('INSERT INTO t VALUES (?, ?, ?)',
(1, datetime.datetime(2026, 5, 4, 12, 34, 56), Decimal('1234.56')))
cur.execute('SELECT id FROM t WHERE d > ?', (datetime.date(2025, 1, 1),))
The 2-byte length-prefix discovery: both my Phase 6.a DECIMAL encoder
and the new Phase 6.c DATETIME encoder produced "correct" BCD bytes
but the server silently dropped the SQ_BIND PDU (no response, just
timeout). Captured the wire, diffed against JDBC, and found that
DECIMAL/DATETIME bind data has a 2-byte length PREFIX wrapping the
BCD payload (per Decimal.javaToIfx line 457). With the prefix added,
both encoders work. DATE doesn't need the prefix — it's a fixed
4-byte int.
Per-type wire format:
date → DATE(7), [4-byte BE int = days since 1899-12-31]
datetime → DATETIME(10), [short total_len][byte 0xc7][7 BCD pairs]
Decimal → DECIMAL(5), [short total_len][byte exp][BCD digit pairs]
For DATETIME the encoder always emits YEAR TO SECOND form (no
microseconds) — covers the common case. Phase 6.x can add YEAR TO
FRACTION(N) variants if microsecond precision is needed.
For DECIMAL the encoder uses the asymmetric base-100 complement
(mirror of decoder) for negatives. Tested with positive, negative,
and fractional values.
Lesson for the protocol playbook: when the server silently drops a
PDU, it's almost always an envelope/framing issue rather than the
inner-value bytes being wrong. Same pattern as the SHORT-vs-INT
reserved field in CURNAME+NFETCH and the even-byte alignment pad.
Module changes:
src/informix_db/converters.py:
+ _encode_date — 4-byte BE int day count
+ _encode_datetime — YEAR TO SECOND form with 2-byte length prefix
+ _encode_decimal — re-enabled (was Phase 6.x stub) with the same
length-prefix fix
+ encode_param() dispatches on datetime.datetime BEFORE
datetime.date (since datetime is a subclass of date in Python)
Tests: 40 unit + 73 integration (3 new date/datetime param tests + 1
updated decimal param test) = 113 total, all green, ruff clean. New
tests cover:
- date as INSERT parameter via executemany — 3 dates round-trip
- datetime as INSERT parameter via executemany — 3 timestamps
- date as parameter in a WHERE clause filter (created_at > ?)
- Decimal round trip (was: NotImplementedError check; now: real
INSERT + SELECT verification)
Type support matrix updates:
DATE — encode ✓ + decode ✓ (was decode-only)
DATETIME — encode ✓ + decode ✓ (was decode-only)
DECIMAL — encode ✓ + decode ✓ (was decode-only)
Ryan Malloy
10863a9337