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feat: limit/offset on cog_gov_search() and cog_balances() (#57)
verbs were left materializing everything and slicing in R -- the pattern behind
the 2026-08-06 production incident. cog_gov_search() had no LIMIT at all, so an
unfiltered call returns the entire 40,336-row crosswalk.

Extracted the #39 machinery into R/pagination.R first (.validate_pagination(),
.paginate_sql(), .take_pagination_total()) rather than growing a third inline
copy: three definitions of what total_rows means is three places for it to
drift. Conflict refusals stay at the call sites because each verb's conflict
set differs. .verb_spendrev() now uses the shared helpers and is unchanged in
behaviour.

The empty-page fallback query is now passed as a thunk, so the unpaginated SQL
is only BUILT when an offset actually lands past the end instead of on every
paged call.

Two things #57 did not anticipate:

- cog_gov_search()'s ORDER BY was not a total order. population_acs DESC NULLS
  LAST leaves ties -- and the whole NULL block -- in scan order, so two requests
  can order them differently and a paged sweep duplicates one row while dropping
  another. Added canonical_govid as tiebreaker. Unpaginated output changes only
  in the relative order of already-tied rows.

- Basket mode returns one resolved row per requested name plus a sidecar
  covering all of them, so a page of it is not a page of anything the caller
  asked for. Refused with uscogdata_basket_pagination_conflict rather than
  silently ignoring the arguments.

Both default to NULL, so cog-api adopts them behind its existing formals()
probe with no lockstep deploy.

Suite: 1067 passed, 0 failed, 0 warnings (2 pre-existing live-corpus skips).
2026-08-10 19:27:11 -04:00

217 lines
10 KiB
R

# R/balances.R
#
# Cash and security holdings. A third verb rather than an argument on a money
# verb because holdings are a STOCK -- a balance at a point in time -- while
# cog_spending()/cog_revenue() return FLOWS over a fiscal year. The money
# verbs' whole argument vocabulary (expenditure_concept, revenue_concept,
# complete=) describes flows and is meaningless here, so this deliberately
# does NOT route through .verb_spendrev().
#' Cash and security holdings for one or more governments
#'
#' Returns Census cash-and-security holdings (`category_type = "balance"`):
#' fund balances, retirement system holdings and insurance trust balances.
#'
#' @section Holdings are not GAAP fund balance:
#' Census holdings are **gross** -- no liabilities are netted -- so a reserve
#' ratio built from them overstates what is actually available. They are not
#' comparable to a GAAP fund balance from an ACFR.
#'
#' @param govid Canonical govid(s): a character vector, or a data frame with a
#' `canonical_govid` column (e.g. from [cog_gov_search()]). `NULL` to name
#' the cohort by `state`/`type` instead.
#' @inheritParams cog_spending
#' @param years Integer vector of fiscal years.
#' @param category Optional character vector of categories to keep. One of
#' `"Fund Balances"`, `"Insurance Trust Balances"`,
#' `"Retirement System Holdings"`. There is deliberately no `subtype`
#' argument: for holdings, `category` is a strict coarsening of
#' `balance_subtype` (unlike the money verbs, where the two axes cross), so
#' every combination would be either redundant or empty.
#' `category = "Fund Balances"` is exactly the `general` family
#' (`W01`/`W31`/`W61`). `balance_subtype` is returned, so a finer split is
#' one `dplyr::filter()` away. The reserved pseudo-category
#' `"All Categories"` (see [cog_spending()]) is **not** supported here and
#' errors with class `uscogdata_all_categories_unsupported`: it sums a
#' concept's subtype scope, and holdings are a stock with no concept
#' vocabulary to sum across. Omit `category` to get every category broken
#' out instead.
#' @param per_capita Divide holdings by population. Note this is a **stock per
#' resident** (reserves per person), which is *not* comparable to
#' [cog_spending()]'s per-capita figures -- those are a flow per person.
#' @param adjust_to_year Deflate to this year's dollars (CPI-U).
#' @param basis Accepted for uniformity with the money verbs, but currently a
#' **no-op**: `harmonization_map` carries no balance-code rows, so harmonized
#' and raw space are identical for holdings. Reported in
#' `provenance$basis_note`.
#' @param recipe Optional harmonization recipe id (see [cog_recipes()]).
#' `"cash_securities_z77_wide"` and `"cash_securities_z78_wide"` bridge the
#' wide era to the modern one.
#' @param limit Maximum number of result rows to return, pushed into the SQL
#' rather than applied after materializing every row. `NULL` (default)
#' returns everything. Cannot be combined with `recipe` -- see `offset` and
#' `total_rows`.
#' @param offset Rows to skip before `limit` starts counting (0-based).
#' Ignored if `limit` is `NULL`; defaults to `0L` when `limit` is set.
#'
#' @return Tibble with columns `year`, `canonical_govid`, `gov_name`,
#' `balance_subtype`, `category`, `amt_nominal`, `codes_included`,
#' `aggregate_fallback`, plus optional `amt_per_capita_nominal` and
#' `pop_source` (when `per_capita = TRUE`), optional `amt_real` (when
#' `adjust_to_year` is set), and optional `amt_per_capita_real` (only when
#' **both** `per_capita = TRUE` and `adjust_to_year` are set -- there is no
#' nominal per-capita column to deflate otherwise). Amounts are full US
#' dollars.
#'
#' Carries a `provenance` attribute matching
#' `inst/schemas/provenance-v1.json`, whose `balance_caveats` block reports
#' `not_gaap`, `not_gaap_note`, `coverage_window` (measured year extents for
#' every balance subtype in the mounted corpus, not only the observed ones)
#' and `truncated` (the observed subtypes whose coverage falls short of the
#' requested years). `expenditure_concept`/`revenue_concept` are `NA` --
#' holdings are a stock, not a flow, so neither concept vocabulary applies.
#'
#' When `limit` is set, also carries a `total_rows` attribute: the full
#' unpaginated row count, computed by the same query (`COUNT(*) OVER()`)
#' rather than a second scan.
#' @export
cog_balances <- function(govid = NULL, years, category = NULL,
per_capita = FALSE, adjust_to_year = NULL,
basis = c("harmonized", "raw"), recipe = NULL,
state = NULL, type = NULL,
limit = NULL, offset = NULL) {
call <- match.call()
basis <- match.arg(basis, c("harmonized", "raw"))
# Coerce FIRST, validate second: .validate_verb_inputs() asserts
# is.character(govid), and a data-frame govid (cog_gov_search() output) has
# not been unwrapped yet at this point.
govid <- if (is.null(govid)) NULL else .coerce_govid_input(govid)
# The money verbs' validator, reused rather than re-implemented (R/spending.R).
# It covers the exact superset cog_balances() needs -- including the
# recipe/category mutual-exclusivity guard -- so a second local copy would
# only be a place for the two to drift apart. This is the same kind of
# helper reuse as .build_verb_sql()/.attach_per_capita() below; it does NOT
# route the verb through .verb_spendrev(), which stays deliberately unused
# here because its flow vocabulary is meaningless for a stock.
#
# allow_all_categories is left at its FALSE default (contrast
# .verb_spendrev(), which passes TRUE): the all-categories mode's "sum"
# only means something in terms of a concept's subtype scope, and holdings
# have no concept vocabulary. The reuse above is exactly why this can be a
# one-line default rather than a second bespoke check -- see the
# validator's own doc comment for the incident that made that matter.
.validate_verb_inputs(govid, years, category, per_capita, adjust_to_year,
recipe)
# Same semantics as the money verbs (R/pagination.R). Only the `recipe`
# conflict applies here: cog_balances() has no `complete` argument, and a
# recipe's result comes from .run_recipe()'s own query, which pagination is
# not wired into.
paging <- .validate_pagination(limit, offset)
limit <- paging$limit
offset <- paging$offset
if (!is.null(limit) && !is.null(recipe)) {
cli::cli_abort(c(
"`limit`/`offset` cannot be combined with `recipe`.",
"i" = "A recipe's result comes from a separate query (`.run_recipe()`) that pagination is not wired into yet.",
"*" = "Drop `limit`/`offset`, or drop `recipe`."
), class = "uscogdata_recipe_pagination_conflict")
}
years <- as.integer(years)
if (!is.null(adjust_to_year)) adjust_to_year <- as.integer(adjust_to_year)
cohort <- .make_cohort(govid, state, type)
con <- .ensure_session()
.require_balance_support(con)
scope <- .check_govids_in_scope(govid)
basis_note <- paste0(
"`basis` has no effect on holdings: harmonization_map carries no ",
"balance-code rows, so harmonized and raw space are identical here."
)
manifest <- .uscogdata_env$manifest
recipe_block <- NULL
category_for_prov <- category
total_rows <- NULL # set below only when limit is non-NULL (non-recipe path)
if (!is.null(recipe)) {
.require_schema_v5(con, manifest, "recipe =")
.validate_recipe_id(con, recipe)
comps <- .recipe_components(con, recipe)
recipe_label <- comps$label[[1]]
result <- .run_recipe(con, recipe, cohort, years)
sql <- attr(result, "sql_query")
result <- .shape_recipe_result(result, "balance_subtype", recipe_label)
recipe_block <- list(
recipe_id = recipe, label = recipe_label,
components = .df_to_row_list(comps)
)
category_for_prov <- recipe_label
} else {
sql <- .build_verb_sql("balance_annotated", "balance_subtype",
cohort, years, category,
ig_view = NULL, subtype_scope = NULL,
limit = limit, offset = offset)
result <- tibble::as_tibble(DBI::dbGetQuery(con, sql))
if (!is.null(limit)) {
paged <- .take_pagination_total(result, con, function() {
.build_verb_sql("balance_annotated", "balance_subtype",
cohort, years, category,
ig_view = NULL, subtype_scope = NULL)
})
result <- paged$result
total_rows <- paged$total_rows
}
}
# Order matters (matches .verb_spendrev()): per-capita first, so
# .attach_real_dollars() deflates the nominal per-capita column into
# amt_per_capita_real rather than needing amt_per_capita_nominal recomputed.
if (isTRUE(per_capita)) result <- .attach_per_capita(result, con)
if (!is.null(adjust_to_year)) {
result <- .attach_real_dollars(result, adjust_to_year, per_capita)
}
prov <- .build_provenance(
verb = "cog_balances", call = call, govid = govid, years = years,
category = category_for_prov, per_capita = per_capita,
adjust_to_year = adjust_to_year, result = result, sql = sql,
subtype_col = "balance_subtype",
basis = basis, basis_note = basis_note,
# Neither concept vocabulary applies to a stock.
expenditure_concept = NA_character_,
revenue_concept = NA_character_,
recipe = recipe_block
)
prov$scope$govids_found <- scope$found
prov$scope$govids_missing <- scope$missing
prov$scope$cohort <- .cohort_provenance(con, cohort)
prov$balance_caveats <- .balance_caveats(
con, prov$codes_summed$observed, years
)
.emit_balance_caveats(prov$balance_caveats)
attr(result, "provenance") <- prov
if (!is.null(limit)) attr(result, "total_rows") <- total_rows
result
}
#' Abort unless the mounted corpus classifies balance codes.
#'
#' `balance_subtype` arrived with cog_pipeline #76/#77 without a
#' schema_version bump, so the check is on the column, not the version.
#' @noRd
.require_balance_support <- function(con) {
if (.corpus_has_balance_subtype(con)) return(invisible(TRUE))
cli::cli_abort(
c("This corpus does not classify cash and security holdings.",
i = "`summary_categories` has no {.field balance_subtype} column.",
i = "Republish from cog_pipeline at #76/#77 or later."),
class = "uscogdata_no_balance_support"
)
}