spec_result_fetch
dbFetch() always returns a data.frame
with as many rows as records were fetched and as many columns as fields in the result set, even if the result is a single value or has one or zero rows.
An attempt to fetch from a closed result set raises an error.
If the n argument is not an atomic whole number
greater or equal to -1 or Inf, an error is raised,
but a subsequent call to dbFetch() with proper n argument succeeds.
Calling dbFetch() on a result set from a data manipulation query
created by dbSendStatement()
can be fetched and return an empty data frame, with a warning.
Fetching multi-row queries with one
or more columns by default returns the entire result.
Multi-row queries can also be fetched progressively
by passing a whole number (integer
or numeric)
as the n argument.
A value of Inf for the n argument is supported
and also returns the full result.
If more rows than available are fetched, the result is returned in full
without warning.
If fewer rows than requested are returned, further fetches will
return a data frame with zero rows.
If zero rows are fetched, the columns of the data frame are still fully
typed.
Fetching fewer rows than available is permitted,
no warning is issued when clearing the result set.
A column named row_names is treated like any other column.