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TOC sources

Source: R/toc.R
toc_sources.Rd

Sources are passed, in priority order, to tlf_resolve_titles() and toc_read().

Usage

toc_source_db(conn, table, schema = toc_schema(), label = "database")

toc_source_file(path, schema = toc_schema(), label = basename(path))

toc_source_dir(dir, stem = "toc_snapshot", schema = toc_schema())

toc_source_data(data, schema = toc_schema(), label = "data frame")

Arguments

conn

A DBIConnection, or a function with no arguments returning one.

table

Table name, or a DBI::Id() for schema-qualified names. The name is quoted by DBI, never pasted into SQL.

schema

A toc_schema() mapping for tabular sources.

label

Short description recorded in the provenance of resolved titles.

path

File path.

dir

Directory to search.

stem

File name without extension.

data

A data frame in the layout described by schema.

Value

An object of class toc_source.

Details

  • toc_source_db(): a live database table read through DBI (mode "live").

  • toc_source_file(): a snapshot file (mode "snapshot"). .json, .yml/.yaml (the tlfstack interchange format, see toc_write()), .csv and .rds are supported.

  • toc_source_dir(): finds a snapshot in a directory by trying <stem>.json, <stem>.yml, <stem>.yaml, <stem>.csv and <stem>.rds, in that order.

  • toc_source_data(): an in-memory data frame (mode "snapshot").

Credentials

tlfstack never reads credentials or builds connection strings. Pass either an open DBI connection, which you own and close, or a function with no arguments that returns one. tlfstack calls the function for each read and disconnects afterwards. Keep secrets in your own secret store (for example a keyring, an ODBC DSN, or environment variables read inside your function).

Examples

f <- tempfile(fileext = ".yml")
toc_write(ex_toc, f)
src <- toc_source_file(f)
nrow(toc_read(src))
#> [1] 6
unlink(f)