Convert data frames with cell columns to and from Arrow tables

a5_to_arrow_table() converts a data frame to an Arrow Table, writing a5_cell columns as uint64 and a5_covering columns as list<uint64> (see a5_cell_to_arrow() and a5_covering_to_arrow()), and records the A5 index version (a5_info()$index) in the schema metadata under "a5:index_version". a5_from_arrow_table() reverses it, turning uint64 columns into cells and list<uint64> columns into coverings.

Usage

a5_to_arrow_table(x)

a5_from_arrow_table(x, cells = NULL, coverings = NULL)

Arguments

x

For a5_to_arrow_table(), a data frame. For a5_from_arrow_table(), an Arrow Table, RecordBatch, or anything arrow::as_arrow_table() accepts, such as a query result.

cells, coverings

Names of the columns to read as cells and as coverings, or NULL (the default) for every uint64 and every list<uint64> column respectively.

Value

a5_to_arrow_table(): an Arrow Table. a5_from_arrow_table(): a data frame.

Details

Ids stay exact throughout, never passing through doubles or text, so the pair suits Parquet files and DuckDB queries. A table whose metadata records a different index version is an error, since its ids would name other cells; convert such ids with a5_migrate().

See also

a5_info()

Examples

cells <- a5_lonlat_to_cell(c(-3.19, 135), c(55.95, 0), resolution = 10)
df <- data.frame(cell = cells, value = c(1.5, 2.5))
df$disk <- a5_grid_disk(cells, k = 1)
tbl <- a5_to_arrow_table(df)
tbl$schema
#> Schema
#> cell: uint64
#> value: double
#> disk: list<item: uint64>
#> 
#> See $metadata for additional Schema metadata
back <- a5_from_arrow_table(tbl)
identical(back$cell, df$cell)
#> [1] TRUE