dplyr-glimpse.md
In arrow: Integration to 'Apache' 'Arrow'

glimpse() Table/ChunkedArray

Code
  glimpse(tab)
Output
  Table
  10 rows x 7 columns
  $ int           <int32> 1, 2, 3, NA, 5, 6, 7, 8, 9, 10
  $ dbl          <double> 1.1, 2.1, 3.1, 4.1, 5.1, 6.1, 7.1, 8.1, NA, 10.1
  $ dbl2         <double> 5, 5, 5, 5, 5, 5, 5, 5, 5, 5
  $ lgl            <bool> TRUE, NA, TRUE, FALSE, TRUE, NA, NA, FALSE, FALSE, NA
  $ false          <bool> FALSE, FALSE, FALSE, FALSE, FALSE, FALSE, FALSE, FALSE, ~
  $ chr          <string> "a", "b", "c", "d", "e", NA, "g", "h", "i", "j"
  $ fct <dictionary<...>> a, b, c, d, NA, NA, g, h, i, j
  Call `print()` for full schema details

Code
  glimpse(tab$chr)
Output
  <string> [ [ "a", "b", "c", "d", "e", null, "g", "h", "i", "j" ] ]

glimpse() RecordBatch/Array

Code
  glimpse(batch)
Output
  RecordBatch
  10 rows x 7 columns
  $ int           <int32> 1, 2, 3, NA, 5, 6, 7, 8, 9, 10
  $ dbl          <double> 1.1, 2.1, 3.1, 4.1, 5.1, 6.1, 7.1, 8.1, NA, 10.1
  $ dbl2         <double> 5, 5, 5, 5, 5, 5, 5, 5, 5, 5
  $ lgl            <bool> TRUE, NA, TRUE, FALSE, TRUE, NA, NA, FALSE, FALSE, NA
  $ false          <bool> FALSE, FALSE, FALSE, FALSE, FALSE, FALSE, FALSE, FALSE, ~
  $ chr          <string> "a", "b", "c", "d", "e", NA, "g", "h", "i", "j"
  $ fct <dictionary<...>> a, b, c, d, NA, NA, g, h, i, j
  Call `print()` for full schema details

Code
  glimpse(batch$int)
Output
  <int32> [ 1, 2, 3, null, 5, 6, 7, 8, 9, 10 ]

glimpse() with VctrsExtensionType

Code
  glimpse(haven)
Output
  Table
  2 rows x 3 columns
  $ num            <double> 5.1, 4.9
  $ cat_int <ext<hvn_lbll>> 3, 1
  $ cat_chr <ext<hvn_lbll>> Can't convert `x` <haven_labelled> to <character>.
  Call `print()` for full schema details

Code
  glimpse(haven[[3]])
Output
  <<haven_labelled[0]>> [ [ "B", "B" ] ]

glimpse prints message about schema if there are complex types

Code
  glimpse(dictionary_but_no_metadata)
Output
  Table
  5 rows x 2 columns
  $ a           <int32> 1, 2, 3, 4, 5
  $ b <dictionary<...>> 1, 2, 3, 4, 5
  Call `print()` for full schema details

Code
  glimpse(Table$create(a = 1))
Output
  Table
  1 rows x 1 columns
  $ a <double> 1

glimpse() calls print() instead of showing data for RBR

Code
  example_data %>% as_record_batch_reader() %>% glimpse()
Message
  Cannot glimpse() data from a RecordBatchReader because it can only be read one time; call `as_arrow_table()` to consume it first.
Output
  RecordBatchReader
  int: int32
  dbl: double
  dbl2: double
  lgl: bool
  false: bool
  chr: string
  fct: dictionary<values=string, indices=int8>

Code
  example_data %>% as_record_batch_reader() %>% select(int) %>% glimpse()
Message
  Cannot glimpse() data from a RecordBatchReader because it can only be read one time. Call `compute()` to evaluate the query first.
Output
  RecordBatchReader (query)
  int: int32

  See $.data for the source Arrow object

glimpse() on Dataset

Code
  glimpse(ds)
Output
  FileSystemDataset with 2 Parquet files
  20 rows x 7 columns
  $ int                <int32> 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 101, 102, 103, 104, ~
  $ dbl               <double> 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 51, 52, 53, 54, 55, ~
  $ lgl                 <bool> TRUE, FALSE, NA, TRUE, FALSE, TRUE, FALSE, NA, TRUE~
  $ chr               <string> "a", "b", "c", "d", "e", "f", "g", "h", "i", "j", "~
  $ fct      <dictionary<...>> A, B, C, D, E, F, G, H, I, J, J, I, H, G, F, E, D, ~
  $ ts <timestamp[us, tz=UTC]> 2015-04-30 03:12:39, 2015-05-01 03:12:39, 2015-05-0~
  $ group              <int32> 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 2, 2, 2, 2, 2, 2, ~
  Call `print()` for full schema details

glimpse() on Dataset query only shows data for streaming eval

Code
  ds %>% summarize(max(int)) %>% glimpse()
Message
  This query requires a full table scan, so glimpse() may be expensive. Call `compute()` to evaluate the query first.
Output
  FileSystemDataset (query)
  max(int): int32

  See $.data for the source Arrow object

glimpse() on in-memory query shows data even if aggregating

Code
  example_data %>% arrow_table() %>% summarize(sum(int, na.rm = TRUE)) %>%
    glimpse()
Output
  Table (query)
  ?? rows x 1 columns
  $ `sum(int, na.rm = TRUE)` <int64> 51
  Call `print()` for query details