Environment variables

The Arpeio ADBC drivers use two namespaces of environment variables. This page documents the shared, family-wide ones — the knobs that mean the same thing in every driver. The driver-specific variables live on each driver's own environment-variables page.

Two namespaces

Prefix	Scope	Documented
ARPEIO_ADBC_*	Shared — identical meaning in ArrowTDS, ArrowFEBE, ArrowTTC (and ArrowDRDA)	On this page
ARROW<CODE>_*	Driver / protocol specific — e.g. ARROWTTC_NO_LOB_PREFETCH	Each driver's env-vars page

Every variable lives in exactly one namespace; there is no aliasing between them. When a driver adds a generic knob, it uses the shared prefix from day one, so a trace or an A/B recipe carries across drivers unchanged.

Per-driver pages: ArrowTDS · ArrowFEBE · ArrowTTC

Shared diagnostics (ARPEIO_ADBC_*)

These control diagnostics and low-level behaviour that has no place in a connection string. They are read from the environment, once, at the point they apply.

Variable	Values	Effect
ARPEIO_ADBC_READ_TIMING	1	Emit a per-batch read-timing line and a summary at stream release on stderr, attributing an extract to the wire (recv), the decoder (decode), and the consumer.
ARPEIO_ADBC_WRITE_TIMING	1	Per-batch ingest profiling on the write path (drivers that support ingest timing).
ARPEIO_ADBC_ALLOCATOR	system, mimalloc	Force the column-buffer allocator backend, read once on the first allocation. system always works; mimalloc is honoured only when the driver was built with mimalloc (the default). Used to A/B allocators without a rebuild.
ARPEIO_ADBC_QUIET	1	Silence non-error diagnostic output.

Reading the timing summary

With ARPEIO_ADBC_READ_TIMING=1, each driver prints a summary line at stream release (the tag names the driver, e.g. [TTC READ SUMMARY]):

[READ SUMMARY] batches=61 rows=6001215 wall_ms=2090 busy_ms=2075 \
  recv_ms=72 decode_ms=2003 consumer_ms=2 cpu_ms=2057 blocked_ms=18 \
  MiB=596 MiB/s=285 alloc=mimalloc

• recv_ms — time inside recv() / SSL_read(). High means the wire (or the server) is the bottleneck.
• decode_ms — busy_ms − recv_ms: turning wire bytes into Arrow buffers.
• consumer_ms — wall time spent outside the driver, i.e. waiting for the caller to take each batch. High means the consumer is the bottleneck.
• blocked_ms — busy_ms − cpu_ms: descheduled time the driver was neither on a CPU nor in recv. Under parallel load this is the allocator-contention signal.
• alloc — the resolved allocator backend, system or mimalloc.

Licence (ARPEIO_ADBC_*)

The licence is resolved the same way in every driver. These environment variables are two of the sources checked, in precedence order:

Variable	Values	Effect
ARPEIO_ADBC_LICENCE	inline token	The ARROW LICENCE token itself, if no option is set.
ARPEIO_ADBC_LICENCE_FILE	path	Path to a licence file, if no option is set.

Full resolution order (first match wins): the arpeio.adbc.license / arpeio.adbc.license_file ADBC option → ARPEIO_ADBC_LICENCE / ARPEIO_ADBC_LICENCE_FILE → an arpeio_adbc.lic file next to the driver library. The gate is always enforced — a driver refuses to initialise without a valid token. See any driver's Licensing page (e.g. ArrowTTC → Licensing) for the details.

note

British spelling. The licence variables are LICENCE, not LICENSE (ARPEIO_ADBC_LICENCE_FILE).