paleolimbot opened a new pull request, #14521:
URL: https://github.com/apache/arrow/pull/14521
This makes the default `map_batches()` behaviour lazy (i.e., the function is
called once per batch as each batch arrives):
``` r
library(arrow, warn.conflicts = FALSE)
#> Some features are not enabled in this build of Arrow. Run `arrow_info()`
for more information.
source <- RecordBatchReader$create(
record_batch(a = 1:10),
record_batch(a = 11:20)
)
mapped <- map_batches(source, function(x) {
message("Hi! I'm being evaluated!")
x
}, .schema = source$schema)
as_arrow_table(mapped)
#> Hi! I'm being evaluated!
#> Hi! I'm being evaluated!
#> Table
#> 20 rows x 1 columns
#> $a <int32>
```
<sup>Created on 2022-10-26 with [reprex
v2.0.2](https://reprex.tidyverse.org)</sup>
This was previously a confusing default since piping the resulting
`RecordBatchReader` into an `ExecPlan` would fail for some ExecPlans before
ARROW-17178 (#13706). This PR commits to the (more optimal/expected) lazy
behaviour.
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