paleolimbot opened a new pull request, #211:
URL: https://github.com/apache/arrow-nanoarrow/pull/211
Total proof-of-concept of one way to go about async `stream$get_next()`, as
discussed briefly with @krlmlr, @lidavidm, and @nbenn in connection with ADBC
in R. When the stream is wrapping a database result set, the `get_next()` call
can block for a considerable amount of time...this async version would support
a world where it's easier to cancel running queries since we can loop + wait in
R land (possibly calling the brand-new "cancel" function coming to ADBC 1.1).
This PR currently will leak memory and doesn't communicate any error
information beyond "result code".
Reprex:
``` r
library(nanoarrow)
stream <- basic_array_stream(list(1:5))
# ...more usefully, a promise or future whose value is set from the callback
result <- NULL
nanoarrow:::nanoarrow_array_stream_get_next_async(stream, function(code,
array) {
message("done!")
result <<- array
})
Sys.sleep(0.5)
nanoarrow:::run_callbacks()
#> done!
convert_array(result)
#> [1] 1 2 3 4 5
```
<sup>Created on 2023-06-07 with [reprex
v2.0.2](https://reprex.tidyverse.org)</sup>
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