[GitHub] [arrow] wjones127 commented on a change in pull request #12629: ARROW-15627: [R] Fix union dataset unify schema

[GitBox <gi...@apache.org>]

wjones127 commented on a change in pull request #12629:
URL: https://github.com/apache/arrow/pull/12629#discussion_r830328015



##########
File path: r/tests/testthat/test-dataset.R
##########
@@ -544,6 +557,43 @@ test_that("Creating UnionDataset", {
   expect_error(c(ds1, 42), "character")
 })
 
+test_that("UnionDataset can merge schemas", {
+  sub_df1 <- Table$create(
+    x = Array$create(c(1, 2, 3)),
+    y = Array$create(c("a", "b", "c"))
+  )
+  sub_df2 <- Table$create(
+    x = Array$create(c(4, 5)),
+    z = Array$create(c("d", "e"))
+  )
+
+  path1 <- make_temp_dir()
+  path2 <- make_temp_dir()
+  write_dataset(sub_df1, path1, format = "parquet")
+  write_dataset(sub_df2, path2, format = "parquet")
+
+  ds1 <- open_dataset(path1, format = "parquet")
+  ds2 <- open_dataset(path2, format = "parquet")
+
+  ds <- c(ds1, ds2)
+  actual <- ds %>%
+    collect() %>%
+    arrange(x)
+  expect_equal(
+    actual,
+    union_all(as_tibble(sub_df1), as_tibble(sub_df2))
+  )

Review comment:
       I'm all for making the tests more obvious! 




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