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Stream-filter a dataset/row-groups into a new partitioned dataset

Source: R/table_stream.R
stream_filter.Rd

Reads each partition, filters rows, and writes a new partitioned dataset. Output is written as one partition per input partition (empty partitions are allowed). This avoids materializing all results.

Usage

stream_filter(x, predicate, path = NULL, ...)

Arguments

x

A shard_row_groups or shard_dataset handle.

predicate

Function (chunk, ...) -> logical row mask (length == nrow(chunk)).

path

Output directory. If NULL, a temp dir is created.

...

Passed to predicate().

Value

A shard_dataset handle pointing to the filtered partitions.

Examples

# \donttest{
s <- schema(x = float64())
sink <- table_sink(s, mode = "row_groups")
table_write(sink, 1L, data.frame(x = c(1.0, 2.0, 3.0)))
rg <- table_finalize(sink)
filtered <- stream_filter(rg, predicate = function(chunk) chunk$x > 1.5)
# }