R/spec-meta-get-row-count.R

In r-dbi/DBItest: Testing DBI Backends

#' spec_meta_get_row_count
#' @family meta specifications
#' @usage NULL
#' @format NULL
#' @keywords NULL
spec_meta_get_row_count <- list(
  get_row_count_formals = function() {
    # <establish formals of described functions>
    expect_equal(names(formals(dbGetRowCount)), c("res", "..."))
  },

  row_count_query = function(con) {
    #' @return
    #' `dbGetRowCount()` returns a scalar number (integer or numeric),
    #' the number of rows fetched so far.
    query <- trivial_query()
    #' After calling [dbSendQuery()],
    res <- local_result(dbSendQuery(con, query))
    rc <- dbGetRowCount(res)
    #' the row count is initially zero.
    expect_equal(rc, 0L)
    #' After a call to [dbFetch()] without limit,
    check_df(dbFetch(res))
    rc <- dbGetRowCount(res)
    #' the row count matches the total number of rows returned.
    expect_equal(rc, 1L)
  },
  #
  row_count_query_limited = function(ctx, con) {
    query <- sql_union(.ctx = ctx, trivial_query(), "SELECT 2", "SELECT 3")
    res <- local_result(dbSendQuery(con, query))
    rc1 <- dbGetRowCount(res)
    expect_equal(rc1, 0L)
    #' Fetching a limited number of rows
    check_df(dbFetch(res, 2L))
    #' increases the number of rows by the number of rows returned,
    rc2 <- dbGetRowCount(res)
    expect_equal(rc2, 2L)
    #' even if fetching past the end of the result set.
    check_df(dbFetch(res, 2L))
    rc3 <- dbGetRowCount(res)
    expect_equal(rc3, 3L)
  },
  #
  row_count_query_empty = function(ctx, con) {
    #' For queries with an empty result set,
    query <- sql_union(
      .ctx = ctx, "SELECT * FROM (SELECT 1 as a) a WHERE (0 = 1)"
    )
    res <- local_result(dbSendQuery(con, query))
    rc <- dbGetRowCount(res)
    #' zero is returned
    expect_equal(rc, 0L)
    check_df(dbFetch(res))
    rc <- dbGetRowCount(res)
    #' even after fetching.
    expect_equal(rc, 0L)
  },
  #
  row_count_statement = function(con, table_name) {
    query <- paste0("CREATE TABLE ", table_name, " (a integer)")
    #' For data manipulation statements issued with
    #' [dbSendStatement()],
    res <- local_result(dbSendStatement(con, query))
    rc <- dbGetRowCount(res)
    #' zero is returned before
    expect_equal(rc, 0L)
    expect_warning(check_df(dbFetch(res)))
    rc <- dbGetRowCount(res)
    #' and after calling `dbFetch()`.
    expect_equal(rc, 0L)
  },
  #'
  get_row_count_error = function(con) {
    #' @section Failure modes:
    res <- dbSendQuery(con, trivial_query())
    dbClearResult(res)
    #' Attempting to get the row count for a result set cleared with
    #' [dbClearResult()] gives an error.
    expect_error(dbGetRowCount(res))
  },
  #
  NULL
)