Check Whether a Table Can Be Hashed by datom

Pre-flight check for the datom table contract. Reports, per column, whether datom_write() can hash it and – when it cannot – exactly what to do about it. Run this before a write to fix a table in one pass instead of discovering offenders one error at a time.

Usage

datom_check_hashable(data)

Arguments

data

A data frame to check.

Value

Invisibly, a data frame with one row per column of data and columns:

column

Column name.

class

Collapsed class string, or typeof() when unclassed.

status

"ok" or "unsupported".

recourse

NA when ok, otherwise how to make the column hashable.

Details

datom identifies a table version by a canonical hash of its contents (data_sha), which requires every column to be a supported type: logical, integer, double, character, factor, Date, POSIXct, difftime/hms, data.table::ITime/IDate, bit64::integer64, or a labelled vector over one of those. List columns (including nested data frames, blobs, and POSIXlt), complex, raw, sf geometry, units, and zoo/chron columns are refused with specific advice.

The advice printed here is the same single-source recourse text datom_write() would abort with, so the two can never disagree.

See also

datom_write()

Examples

# A clean table: every column is a supported type
clean <- data.frame(
  id = 1:3,
  score = c(1.5, 2.5, 3.5),
  label = c("a", "b", "c"),
  grp = factor(c("x", "y", "x")),
  day = as.Date(c("2026-01-01", "2026-01-02", "2026-01-03"))
)
datom_check_hashable(clean)
#> ✔ All 5 columns are hashable. This table is ready for `datom_write()`.

# An offending table: a list column and a complex column
messy <- data.frame(id = 1:2)
messy$notes <- list(c("a", "b"), "c")
messy$z <- c(1 + 2i, 3 + 4i)
report <- datom_check_hashable(messy)
#> ✖ 2 of 3 columns are not hashable.
#> ✖ Column notes (<list>): List and blob columns are not hashable. Flatten to one
#>   value per row with tidyr::unnest(), or serialize each element to character
#>   (for example with jsonlite::toJSON() per element), before writing.
#> ✖ Column z (<complex>): Complex columns are not hashable. Split into separate
#>   real and imaginary numeric columns, or convert to character, before writing.
#> ℹ Fix these before `datom_write()`, which refuses the whole table until they are resolved.
report[report$status == "unsupported", c("column", "recourse")]
#>   column
#> 2  notes
#> 3      z
#>                                                                                                                                                                                               recourse
#> 2 List and blob columns are not hashable. Flatten to one value per row with tidyr::unnest(), or serialize each element to character (for example with jsonlite::toJSON() per element), before writing.
#> 3                                                                   Complex columns are not hashable. Split into separate real and imaginary numeric columns, or convert to character, before writing.