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. PEP 249 compliant; sync + async APIs; built-in connection pool; TLS support.

To our knowledge this is the first pure-socket Informix driver in any language — every other Informix driver (IfxPy, the legacy informixdb, ODBC bridges, JPype/JDBC, Perl DBD::Informix) wraps either IBM's CSDK or the JDBC JAR.

pip install informix-db

Quick start

import informix_db

with informix_db.connect(
    host="db.example.com", port=9088,
    user="informix", password="...",
    database="mydb", server="informix",
) as conn:
    cur = conn.cursor()
    cur.execute("SELECT id, name FROM users WHERE id = ?", (42,))
    user_id, name = cur.fetchone()

Async (FastAPI / aiohttp / asyncio)

import asyncio
from informix_db import aio

async def main():
    pool = await aio.create_pool(
        host="db.example.com", user="informix", password="...",
        database="mydb",
        min_size=1, max_size=10,
    )
    async with pool.connection() as conn:
        cur = await conn.cursor()
        await cur.execute("SELECT id, name FROM users WHERE id = ?", (42,))
        row = await cur.fetchone()
    await pool.close()

asyncio.run(main())

Connection pool (sync)

import informix_db

pool = informix_db.create_pool(
    host="db.example.com", user="informix", password="...",
    database="mydb",
    min_size=1, max_size=10, acquire_timeout=5.0,
)

with pool.connection() as conn:
    cur = conn.cursor()
    cur.execute("...")

pool.close()

TLS

import ssl

# Production: bring your own context
ctx = ssl.create_default_context(cafile="/path/to/ca.pem")
informix_db.connect(host="...", port=9089, ..., tls=ctx)

# Dev / self-signed: tls=True disables verification
informix_db.connect(host="127.0.0.1", port=9089, ..., tls=True)

Informix uses dedicated TLS-enabled listener ports (configured server-side in sqlhosts) rather than STARTTLS upgrade — point port at the TLS listener (often 9089) when tls is enabled.

Type support

SQL type	Python type
SMALLINT / INT / BIGINT / SERIAL	int
FLOAT / SMALLFLOAT	float
DECIMAL(p,s) / MONEY	decimal.Decimal
CHAR / VARCHAR / NCHAR / NVCHAR / LVARCHAR	str
BOOLEAN	bool
DATE	datetime.date
DATETIME YEAR TO ...	datetime.datetime / datetime.time / datetime.date
INTERVAL DAY TO FRACTION	datetime.timedelta
INTERVAL YEAR TO MONTH	informix_db.IntervalYM
BYTE / TEXT (legacy in-row blobs)	bytes / str
BLOB / CLOB (smart-LOBs)	informix_db.BlobLocator / informix_db.ClobLocator (read via cursor.read_blob_column, write via cursor.write_blob_column)
ROW(...)	informix_db.RowValue
SET(...) / MULTISET(...) / LIST(...)	informix_db.CollectionValue
NULL	None

Smart-LOB (BLOB / CLOB) read & write

# Read: returns the actual bytes
data = cur.read_blob_column(
    "SELECT data FROM photos WHERE id = ?", (42,)
)

# Write: BLOB_PLACEHOLDER token marks where the BLOB goes
cur.write_blob_column(
    "INSERT INTO photos VALUES (?, BLOB_PLACEHOLDER)",
    blob_data=jpeg_bytes,
    params=(42,),
)

Both work end-to-end in pure Python via the lotofile / filetoblob server functions intercepted at the SQ_FILE (98) wire-protocol level — no thread of native machinery. See docs/DECISION_LOG.md §10–11 for the architecture pivot that made this possible.

Direct stored-procedure invocation (fast-path)

# Cleanly close a smart-LOB descriptor opened via SQL
result = conn.fast_path_call(
    "function informix.ifx_lo_close(integer)", lofd
)
# result == [0] on success

The fast-path RPC (SQ_FPROUTINE / SQ_EXFPROUTINE) bypasses PREPARE → EXECUTE → FETCH for direct UDF/SPL calls. Routine handles are cached per-connection, so repeated calls to the same function take a single round-trip.

Server compatibility

Tested against IBM Informix Dynamic Server 15.0.1.0.3DE (the official icr.io/informix/informix-developer-database Docker image). The wire protocol is stable across modern Informix versions; should work against 12.10+ unmodified.

For features that need server-side configuration (smart-LOBs, logged transactions), see docs/DECISION_LOG.md:

• Phase 7 — logged-DB transactions
• Phase 8 — BYTE/TEXT (needs blobspace)
• Phase 10/11 — BLOB/CLOB (needs sbspace + SBSPACENAME config + level-0 archive)

Standards & guarantees

• PEP 249 (DB-API 2.0): connect(), Connection, Cursor, description, rowcount, exception hierarchy
• paramstyle = "numeric" (Informix's native ESQL/C convention; ? and :1 both work)
• Threadsafety = 1: threads may share the module but not connections; the pool gives per-thread connection access
• CalVer versioning: YYYY.MM.DD releases. PEP 440 post-releases (.1, .2) for same-day fixes.

Development

# Set up the dev environment
uv sync --dev

# Run the test suite (unit-only by default; no Docker needed)
uv run pytest                       # 69 unit tests
uv run pytest -m integration        # 163 integration tests (needs Docker)

# Lint
uv run ruff check src/ tests/

The integration suite expects an Informix Developer Edition container on localhost:9088:

docker compose -f tests/docker-compose.yml up -d

For the smart-LOB tests specifically, the dev container needs additional one-time setup (blobspace + sbspace + level-0 archive). See docs/DECISION_LOG.md §10 for the exact onspaces / onmode / ontape commands.

Project history & design rationale

This driver was built incrementally over 16 phases, each with a focused scope and decision log. The full reasoning trail lives in:

• docs/PROTOCOL_NOTES.md — byte-level SQLI wire-format reference
• docs/JDBC_NOTES.md — index into the decompiled IBM JDBC driver, used as a clean-room reference
• docs/DECISION_LOG.md — phase-by-phase architectural decisions, with the why preserved
• docs/CAPTURES/ — annotated socat hex-dump captures

Notable architectural pivots documented in the decision log:

• Phase 10/11 (smart-LOB read/write): used lotofile/filetoblob SQL functions + SQ_FILE protocol intercept instead of the heavier SQ_FPROUTINE + SQ_LODATA stack — ~3x smaller than originally projected
• Phase 7 (logged-DB transactions): discovered Informix requires explicit SQ_BEGIN before each transaction in non-ANSI mode, plus SQ_RBWORK needs a savepoint short payload
• Phase 16 (async): shipped thread-pool wrapping (~250 lines) instead of full I/O abstraction refactor (~2000 lines); functionally equivalent for typical FastAPI workloads

License

MIT.