read-parquet-5.md
In nanoparquet: Read and Write 'Parquet' Files

read a subset, edge cases

Code
  read_parquet(tmp, col_select = integer())
Output
  # A data frame: 32 x 0
Code
  read_parquet(tmp, col_select = character())
Output
  # A data frame: 32 x 0

error if a column is requested multiple times

Code
  read_parquet(tmp, col_select = c(1, 1))
Condition
  Error in `read_parquet()`:
  ! Column 1 selected multiple times in `read_parquet()`.
Code
  read_parquet(tmp, col_select = c(3, 4, 5, 3))
Condition
  Error in `read_parquet()`:
  ! Column 3 selected multiple times in `read_parquet()`.
Code
  read_parquet(tmp, col_select = c(3:4, 4:3))
Condition
  Error in `read_parquet()`:
  ! Columns 3, 4 selected multiple times in `read_parquet()`.
Code
  read_parquet(tmp, col_select = "foo")
Condition
  Error in `read_parquet()`:
  ! Column foo does not exist in Parquet file
Code
  read_parquet(tmp, col_select = c("foo", "bar"))
Condition
  Error in `read_parquet()`:
  ! Columns foo, bar do not exist in Parquet file
Code
  read_parquet(tmp, col_select = c("nam", "nam"))
Condition
  Error in `read_parquet()`:
  ! Column nam selected multiple times in `read_parquet()`.
Code
  read_parquet(tmp, col_select = c("cyl", "disp", "hp", "cyl"))
Condition
  Error in `read_parquet()`:
  ! Column cyl selected multiple times in `read_parquet()`.
Code
  read_parquet(tmp, col_select = c("cyl", "disp", "disp", "cyl"))
Condition
  Error in `read_parquet()`:
  ! Columns cyl, disp selected multiple times in `read_parquet()`.

mixing RLE_DICTIONARY and PLAIN

Code
  as.data.frame(read_parquet_schema(pf)[, c("type", "repetition_type")])
Output
          type repetition_type
  1       <NA>        REQUIRED
  2      INT32        REQUIRED
  3      INT64        REQUIRED
  4 BYTE_ARRAY        REQUIRED
  5      FLOAT        REQUIRED
  6     DOUBLE        REQUIRED
  7      INT96        REQUIRED
Code
  as.data.frame(read_parquet_pages(pf)[, c("page_type", "num_values", "encoding")])
Output
           page_type num_values       encoding
  1  DICTIONARY_PAGE        400          PLAIN
  2        DATA_PAGE       1024 RLE_DICTIONARY
  3        DATA_PAGE       1024          PLAIN
  4        DATA_PAGE        352          PLAIN
  5  DICTIONARY_PAGE        400          PLAIN
  6        DATA_PAGE       1024 RLE_DICTIONARY
  7        DATA_PAGE       1024          PLAIN
  8        DATA_PAGE        352          PLAIN
  9  DICTIONARY_PAGE        400          PLAIN
  10       DATA_PAGE       1024 RLE_DICTIONARY
  11       DATA_PAGE       1024          PLAIN
  12       DATA_PAGE        352          PLAIN
  13 DICTIONARY_PAGE        400          PLAIN
  14       DATA_PAGE       1024 RLE_DICTIONARY
  15       DATA_PAGE       1024          PLAIN
  16       DATA_PAGE        352          PLAIN
  17 DICTIONARY_PAGE        400          PLAIN
  18       DATA_PAGE       1024 RLE_DICTIONARY
  19       DATA_PAGE       1024          PLAIN
  20       DATA_PAGE        352          PLAIN
  21 DICTIONARY_PAGE        400          PLAIN
  22       DATA_PAGE       1024 RLE_DICTIONARY
  23       DATA_PAGE       1024          PLAIN
  24       DATA_PAGE        352          PLAIN

Code
  as.data.frame(read_parquet_schema(pf)[, c("type", "repetition_type")])
Output
          type repetition_type
  1       <NA>        REQUIRED
  2      INT32        REQUIRED
  3      INT64        REQUIRED
  4 BYTE_ARRAY        REQUIRED
  5      FLOAT        REQUIRED
  6     DOUBLE        REQUIRED
  7      INT96        REQUIRED
Code
  as.data.frame(read_parquet_pages(pf)[, c("page_type", "num_values", "encoding")])
Output
           page_type num_values       encoding
  1  DICTIONARY_PAGE        400          PLAIN
  2        DATA_PAGE       1024 RLE_DICTIONARY
  3        DATA_PAGE       1024 RLE_DICTIONARY
  4        DATA_PAGE        352 RLE_DICTIONARY
  5  DICTIONARY_PAGE        400          PLAIN
  6        DATA_PAGE       1024 RLE_DICTIONARY
  7        DATA_PAGE       1024 RLE_DICTIONARY
  8        DATA_PAGE        352 RLE_DICTIONARY
  9  DICTIONARY_PAGE        400          PLAIN
  10       DATA_PAGE       1024 RLE_DICTIONARY
  11       DATA_PAGE       1024 RLE_DICTIONARY
  12       DATA_PAGE        352 RLE_DICTIONARY
  13 DICTIONARY_PAGE        400          PLAIN
  14       DATA_PAGE       1024 RLE_DICTIONARY
  15       DATA_PAGE       1024 RLE_DICTIONARY
  16       DATA_PAGE        352 RLE_DICTIONARY
  17 DICTIONARY_PAGE        400          PLAIN
  18       DATA_PAGE       1024 RLE_DICTIONARY
  19       DATA_PAGE       1024 RLE_DICTIONARY
  20       DATA_PAGE        352 RLE_DICTIONARY
  21 DICTIONARY_PAGE        400          PLAIN
  22       DATA_PAGE       1024 RLE_DICTIONARY
  23       DATA_PAGE       1024 RLE_DICTIONARY
  24       DATA_PAGE        352 RLE_DICTIONARY

Code
  as.data.frame(read_parquet_schema(pf)[, c("type", "repetition_type")])
Output
          type repetition_type
  1       <NA>        REQUIRED
  2      INT32        OPTIONAL
  3      INT64        OPTIONAL
  4 BYTE_ARRAY        OPTIONAL
  5      FLOAT        OPTIONAL
  6     DOUBLE        OPTIONAL
  7      INT96        OPTIONAL
Code
  as.data.frame(read_parquet_pages(pf)[, c("page_type", "num_values", "encoding")])
Output
           page_type num_values       encoding
  1  DICTIONARY_PAGE       1009          PLAIN
  2        DATA_PAGE       1024 RLE_DICTIONARY
  3        DATA_PAGE       1024          PLAIN
  4        DATA_PAGE        352          PLAIN
  5  DICTIONARY_PAGE       1018          PLAIN
  6        DATA_PAGE       1024 RLE_DICTIONARY
  7        DATA_PAGE       1024          PLAIN
  8        DATA_PAGE        352          PLAIN
  9  DICTIONARY_PAGE       1014          PLAIN
  10       DATA_PAGE       1024 RLE_DICTIONARY
  11       DATA_PAGE       1024          PLAIN
  12       DATA_PAGE        352          PLAIN
  13 DICTIONARY_PAGE       1013          PLAIN
  14       DATA_PAGE       1024 RLE_DICTIONARY
  15       DATA_PAGE       1024          PLAIN
  16       DATA_PAGE        352          PLAIN
  17 DICTIONARY_PAGE       1018          PLAIN
  18       DATA_PAGE       1024 RLE_DICTIONARY
  19       DATA_PAGE       1024          PLAIN
  20       DATA_PAGE        352          PLAIN
  21 DICTIONARY_PAGE       1016          PLAIN
  22       DATA_PAGE       1024 RLE_DICTIONARY
  23       DATA_PAGE       1024          PLAIN
  24       DATA_PAGE        352          PLAIN

mixing RLE_DICTIONARY and PLAIN, DECIMAL

Code
  as.data.frame(read_parquet_schema(pf)[, c("type", "repetition_type")])
Output
                    type repetition_type
  1                 <NA>        REQUIRED
  2 FIXED_LEN_BYTE_ARRAY        REQUIRED
  3 FIXED_LEN_BYTE_ARRAY        OPTIONAL
Code
  as.data.frame(read_parquet_pages(pf)[, c("page_type", "num_values", "encoding")])
Output
          page_type num_values       encoding
  1 DICTIONARY_PAGE        400          PLAIN
  2       DATA_PAGE       1024 RLE_DICTIONARY
  3       DATA_PAGE        176          PLAIN
  4 DICTIONARY_PAGE        400          PLAIN
  5       DATA_PAGE       1024 RLE_DICTIONARY
  6       DATA_PAGE        176          PLAIN

Code
  as.data.frame(read_parquet_schema(pf)[, c("type", "repetition_type")])
Output
     type repetition_type
  1  <NA>        REQUIRED
  2 INT32        REQUIRED
  3 INT32        OPTIONAL
  4 INT64        REQUIRED
  5 INT64        OPTIONAL
Code
  as.data.frame(read_parquet_pages(pf)[, c("page_type", "num_values", "encoding")])
Output
           page_type num_values       encoding
  1  DICTIONARY_PAGE        400          PLAIN
  2        DATA_PAGE       1024 RLE_DICTIONARY
  3        DATA_PAGE        176          PLAIN
  4  DICTIONARY_PAGE        400          PLAIN
  5        DATA_PAGE       1024 RLE_DICTIONARY
  6        DATA_PAGE        176          PLAIN
  7  DICTIONARY_PAGE        400          PLAIN
  8        DATA_PAGE       1024 RLE_DICTIONARY
  9        DATA_PAGE        176          PLAIN
  10 DICTIONARY_PAGE        400          PLAIN
  11       DATA_PAGE       1024 RLE_DICTIONARY
  12       DATA_PAGE        176          PLAIN

mixing RLE_DICTIONARY and PLAIN, BYTE_ARRAY

Code
  as.data.frame(read_parquet_schema(pf)[, c("type", "repetition_type")])
Output
          type repetition_type
  1       <NA>        REQUIRED
  2 BYTE_ARRAY        REQUIRED
  3 BYTE_ARRAY        OPTIONAL
Code
  as.data.frame(read_parquet_pages(pf)[, c("page_type", "num_values", "encoding")])
Output
          page_type num_values       encoding
  1 DICTIONARY_PAGE        400          PLAIN
  2       DATA_PAGE       1024 RLE_DICTIONARY
  3       DATA_PAGE        176          PLAIN
  4 DICTIONARY_PAGE        400          PLAIN
  5       DATA_PAGE       1024 RLE_DICTIONARY
  6       DATA_PAGE        176          PLAIN

mixing RLE_DICTIONARY and PLAIN, FLOAT16

Code
  as.data.frame(read_parquet_schema(pf)[, c("type", "repetition_type")])
Output
                    type repetition_type
  1                 <NA>        REQUIRED
  2 FIXED_LEN_BYTE_ARRAY        REQUIRED
  3 FIXED_LEN_BYTE_ARRAY        OPTIONAL
Code
  as.data.frame(read_parquet_pages(pf)[, c("page_type", "num_values", "encoding")])
Output
          page_type num_values       encoding
  1 DICTIONARY_PAGE        400          PLAIN
  2       DATA_PAGE       1024 RLE_DICTIONARY
  3       DATA_PAGE        176          PLAIN
  4 DICTIONARY_PAGE        401          PLAIN
  5       DATA_PAGE       1024 RLE_DICTIONARY
  6       DATA_PAGE        176          PLAIN