jonkeane commented on code in PR #38917:
URL: https://github.com/apache/arrow/pull/38917#discussion_r1518585262
##########
r/tests/testthat/test-schema.R:
##########
@@ -315,5 +315,14 @@ test_that("schema extraction", {
adq <- as_adq(example_data)
expect_equal(schema(adq), adq$.data$schema)
+})
+test_that("schema print truncation", {
+ tbl <- arrow_table(example_data)
+ out <- print_schema_fields(schema(tbl), truncate = TRUE, max_fields = 1)
+ expect_output(
+ cat(out),
+ "int: int32\n...\n6 more columns\nUse `schema()` to see entire schema",
+ fixed = TRUE
+ )
Review Comment:
I assume we already cover the `n_fields < max_fields` case in other tests,
yeah?
What happens if `max_fields` is 0 or negative? We might not need to
specifically catch these in code, since if I'm reading correctly no end user
would ever be able to control that, right? But maybe a comment would be good?
##########
r/R/record-batch-reader.R:
##########
@@ -100,7 +100,11 @@ RecordBatchReader <- R6Class("RecordBatchReader",
read_table = function() Table__from_RecordBatchReader(self),
Close = function() RecordBatchReader__Close(self),
export_to_c = function(stream_ptr) ExportRecordBatchReader(self,
stream_ptr),
- ToString = function() self$schema$ToString(),
+ ToString = function() {
+ n_fields_out <- paste0(length(self$schema$fields), " columns", "\n")
+ schema <- self$schema$ToString(truncate = TRUE)
+ paste0(n_fields_out, schema)
+ },
Review Comment:
There is only one other copy of this, so there's not _a huge amount of
benefit_ but do you want to factor this into a helper function and use it here
+ for `Dataset$ToString()`
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