Ryan Malloy
d04000dfc3
Before:
ProgrammingError: server returned SQ_ERR sqlcode=-201 isamcode=0
After:
ProgrammingError: [-201] A syntax error has occurred (offset 1)
ProgrammingError: [-206] The specified table is not in the database
(near 'no_such_table') [ISAM -111] (offset 27)
IntegrityError: [-268] Cannot insert duplicate value -
violates UNIQUE constraint (near 'on table u')
[ISAM -100] (offset 23)
IntegrityError: [-391] Cannot insert NULL value into a NOT NULL column
(near 't.id') (offset 23)
OperationalError: [-255] Not in transaction
PEP 249 exception classes mapped from sqlcode:
-201, -206, -217, -286, -310, ... → ProgrammingError
-239, -268, -291, -292, -391, -703 → IntegrityError
-255, -256, -407, -440, -908, ... → OperationalError
-329, -349, -510 → NotSupportedError
others → DatabaseError (safe fallback)
SQ_ERR wire decode (per IfxSqli.receiveError line 2717):
[short sqlcode][short isamcode][int offset]
[short near_token_len][bytes name][optional pad][short SQ_EOT]
The "near" token is the object name where the error occurred (table or
column name for "not found" errors); empty for most syntax errors.
Structured fields attached to every Informix error for programmatic
inspection:
e.sqlcode — Informix error code (e.g. -206)
e.isamcode — ISAM/RSAM-level error (e.g. -111 = "table not found")
e.offset — character offset in the SQL where the error occurred
e.near — object name in the "near 'XYZ'" clause (or "")
Connection state survives errors: a failed query doesn't poison the
session — subsequent execute() calls work normally. Verified by
test_connection_survives_query_error.
Built-in error catalog of ~50 most common Informix sqlcodes shipped
in src/informix_db/_errcodes.py. Users can extend at runtime with
register_error_text(code, text). Unknown codes get a generic
"Informix error <N>" with structured fields still populated.
Module changes:
src/informix_db/_errcodes.py (new) — error catalog + exception
classification + register_error_text()
src/informix_db/cursors.py — _raise_sq_err now uses the catalog
src/informix_db/connections.py — same upgrade for the connection-side
SQ_ERR path (catches commit/rollback errors etc.)
Tests: 40 unit + 63 integration (8 new error tests) = 103 total, all
green, ruff clean. Tests cover:
- syntax error → ProgrammingError(-201)
- table not found → ProgrammingError(-206) with near='no_such_table'
- column not found → ProgrammingError(-217)
- UNIQUE violation → IntegrityError(-268)
- NOT NULL violation → IntegrityError(-391)
- commit on unlogged DB → OperationalError(-255)
- connection survives errors (subsequent queries work)
- all errors carry structured sqlcode/isamcode/offset/near attrs
informix-db
Pure-Python driver for IBM Informix IDS, speaking the SQLI wire protocol over raw sockets. No IBM Client SDK. No JVM. No native libraries.
Status
🟢 Phase 1 complete. connect() / close() work end-to-end against a real Informix server. Cursor / execute / fetch land in Phase 2.
To our knowledge this is the first pure-socket Informix driver in any language — every other Informix driver (IfxPy, the legacy informixdb, ODBC bridges, Perl DBD::Informix) wraps either IBM's CSDK or the JDBC JAR.
Quick start
import informix_db
with informix_db.connect(
host="127.0.0.1", port=9088,
user="informix", password="in4mix",
database="sysmaster", server="informix",
) as conn:
# cursor() / execute() / fetchone() arrive in Phase 2
pass
Test against the official Informix dev container
docker compose -f tests/docker-compose.yml up -d # IBM Developer Edition, pinned by digest
uv sync --extra dev
uv run pytest # 34 unit tests (no Docker needed)
uv run pytest -m integration # 6 integration tests (needs the container)
Phase 0 artifacts (still useful — they ARE the public reference)
docs/PROTOCOL_NOTES.md— byte-level wire-format reference, derived from packet captures + JDBC decompilation, validated against a real serverdocs/JDBC_NOTES.md— index into the decompiled IBM JDBC driver's wire-protocol classesdocs/DECISION_LOG.md— running rationale for protocol / auth / type decisionsdocs/CAPTURES/— socat hex-dump captures of three reference scenarios (connect, SELECT, full DML cycle)tests/reference/RefClient.java— re-runnable JDBC ground-truth client for capturing fresh traces
License
MIT.