feat: Add temporary argument to duckdb_read_csv()

[ThomasSoeiro]

Here is a try for #142

@krlmlr: You suggested to modify the SQL and to use tbl_function().

I do not understand why it is needed. Cannot we just pass temporary to dbCreateTable() like I did? Can you please clarify?

Warning: this example will overwrite test.db and iris.csv files on your disk if present.

library(duckdb)
con <- dbConnect(duckdb(), dbdir = "test.db")

write.csv(iris, "iris.csv", row.names = FALSE)

duckdb_read_csv(con, "iris_temp_false", "iris.csv")
duckdb_read_csv(con, "iris_temp_true", "iris.csv", temporary = TRUE)

dbListTables(con)
# [1] "iris_temp_false" "iris_temp_true" 

dbReadTable(con, "iris_temp_false") |> head()
#   Sepal.Length Sepal.Width Petal.Length Petal.Width Species
# 1          5.1         3.5          1.4         0.2  setosa
# 2          4.9         3.0          1.4         0.2  setosa
# 3          4.7         3.2          1.3         0.2  setosa
# 4          4.6         3.1          1.5         0.2  setosa
# 5          5.0         3.6          1.4         0.2  setosa
# 6          5.4         3.9          1.7         0.4  setosa

dbReadTable(con, "iris_temp_true") |> head()
#   Sepal.Length Sepal.Width Petal.Length Petal.Width Species
# 1          5.1         3.5          1.4         0.2  setosa
# 2          4.9         3.0          1.4         0.2  setosa
# 3          4.7         3.2          1.3         0.2  setosa
# 4          4.6         3.1          1.5         0.2  setosa
# 5          5.0         3.6          1.4         0.2  setosa
# 6          5.4         3.9          1.7         0.4  setosa

dbDisconnect(con)

Check that the temporary table is gone:

con <- dbConnect(duckdb::duckdb(), dbdir = "test.db")

dbListTables(con)
# [1] "iris_temp_false"

dbDisconnect(con)

[krlmlr]

Thanks, I was confused and thought there's a COPY TEMPORARY ... FROM syntax for disambiguation. There doesn't seem to be one: https://duckdb.org/docs/sql/statements/copy.html#copy--from .

Can you please also add a test?

[krlmlr]

We'd want to check that the ellipsis is actually empty. This is touching the same file, but the move of the ellipsis and the check could also be a separate PR.

[ThomasSoeiro]

I have added a warning. Is it what you wanted?

[krlmlr]

Thanks!

[ThomasSoeiro]

Hi @krlmlr,
Do we need anything else so that this PR can be merged?
Thanks!

[krlmlr]

Thanks for the nudge. I thought I had turned on auto-merge for this PR.