Stream group-wise count

Counts rows per group across partitions without collecting. Optimized for factor groups (factor_col()).

Usage

stream_group_count(x, group)

Arguments

x

A shard_row_groups or shard_dataset handle.

group

Group column name (recommended: factor_col()).

Value

A data.frame with columns group (factor) and n (integer).

Examples

# \donttest{
s <- schema(g = factor_col(c("a", "b")), x = float64())
sink <- table_sink(s, mode = "row_groups")
table_write(sink, 1L,
  data.frame(g = factor(c("a", "b", "a"), levels = c("a", "b")), x = c(1, 2, 3)))
rg <- table_finalize(sink)
stream_group_count(rg, "g")
#>   group n
#> 1     a 2
#> 2     b 1
# }