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feat: cog_open() honours a DuckDB thread and memory budget (#60)
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cog_open() connected with a bare dbConnect() and set no resource pragmas, so
DuckDB claimed every visible core. Right for one interactive session on a
dedicated machine; wrong for a server, where cog-api runs two replicas on an
8-core host budgeted 4 and each replica independently claims all 8.

USCOGDATA_DUCKDB_THREADS and USCOGDATA_DUCKDB_MEMORY_LIMIT now resolve through
.cfg() -- inheriting the env var > option > default precedence USCOGDATA_URL
already had -- and are applied as pragmas when the connection is created.

Unset issues NO pragma, so an unconfigured session is byte-identical to before.
That negative property is asserted directly against a connection opened the
pre-change way rather than against a hardcoded core count.

.cfg() returns an env var as character, so both resolvers coerce and validate
rather than trusting the type: sprintf("SET threads TO %d", "4") would
otherwise abort inside the connection path with an error naming the pragma
instead of the setting the operator got wrong.

Replaces cog-api's getFromNamespace(".ensure_session", "uscogdata") workaround,
which depended on a private name and on the session already being open.
This commit is contained in:
jared
2026-08-10 18:51:56 -04:00
parent 9508b98676
commit f4ab9b6d90
5 changed files with 255 additions and 2 deletions
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NEWS.md
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@@ -1,5 +1,24 @@
# uscogdata 0.4.0
## DuckDB's resource budget is configurable
`USCOGDATA_DUCKDB_THREADS` and `USCOGDATA_DUCKDB_MEMORY_LIMIT` (with matching
`options(uscogdata.duckdb_threads = )` / `options(uscogdata.duckdb_memory_limit = )`
spellings) cap the DuckDB connection the package opens. Both follow the same
env-var > option > default precedence as `USCOGDATA_URL`.
Unset, **no pragma is issued at all** and DuckDB's own defaults apply exactly as
before -- every visible core. That is right for one interactive session on a
dedicated machine and wrong for a server: where several readers share a host, each
otherwise claims the whole machine and they contend. Capping measured ~5% on a
single-government all-years query (502 ms at 2 threads vs 475 ms uncapped on 16
cores), which is cheap enough that a server should always cap.
This replaces a workaround in which a consumer reached into the package namespace
at boot -- `getFromNamespace(".ensure_session", "uscogdata")()` followed by a manual
`SET threads` -- depending both on a private name and on the session already being
open.
## Cohorts can be named by predicate, not just by id
`cog_spending()`, `cog_revenue()` and `cog_balances()` gain optional `state`