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.
177 lines
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177 lines
8.2 KiB
Markdown
# uscogdata 0.4.0
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## DuckDB's resource budget is configurable
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`USCOGDATA_DUCKDB_THREADS` and `USCOGDATA_DUCKDB_MEMORY_LIMIT` (with matching
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`options(uscogdata.duckdb_threads = )` / `options(uscogdata.duckdb_memory_limit = )`
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spellings) cap the DuckDB connection the package opens. Both follow the same
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env-var > option > default precedence as `USCOGDATA_URL`.
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Unset, **no pragma is issued at all** and DuckDB's own defaults apply exactly as
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before -- every visible core. That is right for one interactive session on a
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dedicated machine and wrong for a server: where several readers share a host, each
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otherwise claims the whole machine and they contend. Capping measured ~5% on a
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single-government all-years query (502 ms at 2 threads vs 475 ms uncapped on 16
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cores), which is cheap enough that a server should always cap.
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This replaces a workaround in which a consumer reached into the package namespace
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at boot -- `getFromNamespace(".ensure_session", "uscogdata")()` followed by a manual
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`SET threads` -- depending both on a private name and on the session already being
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open.
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## Cohorts can be named by predicate, not just by id
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`cog_spending()`, `cog_revenue()` and `cog_balances()` gain optional `state`
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and `type` arguments. Both default to `NULL`, so every existing call behaves
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exactly as before.
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Passing them expresses the cohort as a subquery against `canonical_fips_xwalk`
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inside each statement, instead of round-tripping the ids through R and
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rendering them back into a literal `IN` list:
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```r
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# before: resolve 20,106 ids in R, then embed them in every statement
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ids <- cog_gov_search(NULL, state = "CA", type = "city")$canonical_govid
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cog_spending(ids, years = 2022)
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# now: the cohort never leaves the database
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cog_spending(years = 2022, state = "CA", type = "city")
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```
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Measured against the production corpus, same FY2022 aggregate over the
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20,106-government `type = "city"` cohort:
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| cohort expressed as | time |
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|---|---:|
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| `IN (20,106 literals)` | 449 ms |
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| join against a temp cohort table | 99 ms |
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| predicate on `canonical_fips_xwalk` | **94 ms** |
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| no cohort filter at all (the floor) | 88 ms |
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**4.8x, within 7% of the floor.** The rendered `IN` list was 301,591
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characters and was re-parsed in 5-8 separate statements per call, so the cost
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was paid repeatedly; the predicate's size is constant in the cohort.
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`state` and `type` use the same vocabulary and the same internal coercion as
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`cog_gov_search()` -- `state` is a postal abbreviation (`"WI"`) even though the
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crosswalk column holds a FIPS code (`"55"`).
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Supplying `govid` **and** `state`/`type` intersects them: the governments in
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`govid` that also match the predicate. Naming no cohort at all now aborts with
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class `uscogdata_no_cohort` rather than R's "argument is missing" error.
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When the cohort is named by predicate there is no id list to report, so
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`provenance$scope$govids_found`/`govids_missing` are empty and
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`provenance$scope$cohort` carries `state`, `type` and `n_governments` instead.
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A `govid`-named cohort's provenance is unchanged.
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## Fixes
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* An unknown `state` abbreviation now aborts with "Unknown state abbreviation"
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(class `uscogdata_unknown_state`) instead of base R's "subscript out of
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bounds". `.state_abbrev_to_fips` is a named character vector, so `[[` on an
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absent name threw before the curated message could be reached -- making that
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message unreachable dead code in every verb that takes a `state`.
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# uscogdata 0.3.0
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First public release.
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`uscogdata` provides curated R verbs over the Civilytics US Census of
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Governments finance corpus: unit-level financial profiles, geographic rollups
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and peer comparisons, with auditable provenance on every result.
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## What it covers
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Government types 0-3 (state, county, municipality, township), FY1967-FY2024 --
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56 fiscal years, 46,148,034 rows, 190.6 MB. There is no source data for FY1968
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or FY1969. Special districts (type 4) and school districts (type 5) are out of
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scope pending validation.
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## The verbs
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`cog_spending()`, `cog_revenue()` and `cog_balances()` for flows and holdings;
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`cog_gov_search()` to resolve place names (including basket mode for many at
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once); `cog_find_peers()` and `cog_peer_compare()` for cohorts;
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`cog_geographic_rollup()` for aggregates; `cog_categories()`, `cog_recipes()`,
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`cog_manifest()` and `cog_explain()` for metadata and provenance; and
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`cog_mirror()` for a local copy of the corpus.
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## Reading the corpus now works out of the box
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* The package reads the published corpus over HTTPS **with no configuration**.
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Previously the default was a placeholder sentinel and no document in the
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package supplied a working URL, so a new user had no path to a session.
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* Remote reads work at all. The partitioned view used a glob, and DuckDB
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cannot expand a glob over generic HTTP -- there is no directory listing to
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expand against. Partition paths are now enumerated from the corpus manifest,
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which is host-agnostic: an HTTPS mirror, a Nextcloud share and a local
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`cog_mirror()` copy all take the same path.
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* Nothing is written to disk in remote mode; DuckDB fetches only the row
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groups a query needs.
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## Four things to know before your first query
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* **Amounts are in full US dollars.** The raw Census files report thousands;
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the verbs multiply by 1000 on the way out. Do not multiply again.
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* **Multi-government aggregates disclose their coverage.** The Census is a
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complete enumeration only in years ending in 2 and 7; every other year is a
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sample. Every such result carries `provenance$coverage` with per-year
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`n_units_reporting`.
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* **Absence means two different things.** Before FY2012 an absent cell means
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Census published $0; from FY2012 it means not reported. `complete = TRUE`
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labels which.
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* **Series breaks reach you unasked.** Catalogued breaks intersecting your
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query appear in provenance and in `cog_explain()`.
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## Known limits
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* Special districts (type 4) and school districts (type 5) are out of scope.
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* Per-capita rollups exclude governments with no F-33 population, which is by
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design but does silently narrow a rollup.
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* `n_units_reporting` is category-conditional and is not a response rate.
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* Employee-retirement (`X`) codes stop at FY2016, when those systems moved to
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the Annual Survey of Public Pensions.
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# uscogdata 0.2.0
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## New features
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* `cog_spending()` and `cog_revenue()` accept the reserved category
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`"All Categories"`, returning one summed row per
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`(year, canonical_govid, subtype)` across every category inside the
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requested concept's subtype scope. Filtering the result to
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`spend_subtype == "operations"` gives an operating-expenditure total.
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`cog_geographic_rollup()` inherits it,
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which is the efficient way to build a geographic total — previously a
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caller had to issue one rollup per category and sum the results
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(cog-api#37).
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`"All Categories"` is not the same thing as `expenditure_concept = "total"`.
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The concept chooses which subtypes are in scope; `"All Categories"` chooses
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whether the rows inside that scope are broken out or summed.
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* `cog_categories()` advertises `"All Categories"` for the expenditure and
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revenue vocabularies, so the reserved value is discoverable.
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* Coverage signposting (see "Signposting now catches partially-suppressed
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categories" below) now also works in `category = "All Categories"` mode.
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The recipe-suggestion candidate query used to be scoped by `category`,
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which is never a match for the reserved `"All Categories"` value, so
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`provenance$suggestions` always came back empty there — the one mode whose
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whole point is "you cannot sum the wrong scope" was silently unable to
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signal a wrong scope. The candidate query is now scoped by the concept's
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subtype allowlist instead, symmetric with how `.build_verb_sql()` itself
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scopes the summed total: Los Angeles County FY2011, `category = "All
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Categories"` still excludes $271,589,000 of aggregate-published Public
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Welfare (`E68`), but now names `recipe = "welfare_cash_e68_wide"` to
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recover it instead of reporting zero suggestions.
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## Documentation
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* `cog_geographic_rollup()` and `cog_peer_compare()` now document that
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`provenance$coverage`'s `n_units_reporting` is **category-conditional** and
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is not a response rate: a government that was surveyed and genuinely spends
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nothing in the requested category is indistinguishable from one never
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surveyed (uscogdata#36).
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