Closed
Description
I'm not exactly sure why this is happening, but using the sql translation of CAST(x as NUMERIC) does not actually cast an integer to a double value in SQLlite.
I would've thought that it would work, because the documentation seems to suggest this would be the expected behavior, but maybe I am reading it wrong.
https://www.sqlite.org/datatype3.html#affname
At the very least, I think an "easy" solution would just be providing a translation for as.double and as.numeric that casts to REAL or DOUBLE rather than the base scalar default of NUMERIC
library(dplyr)
library(DBI)
con <- dbConnect(RSQLite::SQLite(), ":memory:")
ex <- data.frame(x = 1L)
copy_to(con, ex)
ex_tbl <- tbl(con, "ex")
# it is an integer, as expected
ex_tbl
#> # Source: table<ex> [?? x 1]
#> # Database: sqlite 3.22.0 [:memory:]
#> x
#> <int>
#> 1 1
# no conversion done
mutate(ex_tbl, xx = as.double(x))
#> # Source: lazy query [?? x 2]
#> # Database: sqlite 3.22.0 [:memory:]
#> x xx
#> <int> <int>
#> 1 1 1
# sql maybe incorrect?
mutate(ex_tbl, xx = as.double(x)) %>%
show_query()
#> <SQL>
#> SELECT `x`, CAST(`x` AS NUMERIC) AS `xx`
#> FROM `ex`
# confirming that it does not work manually
res_int <- dbGetQuery(con, "SELECT CAST(x as NUMERIC) as xx FROM ex")
class(res_int$xx)
#> [1] "integer"
# casting to REAL or DOUBLE works
res_dbl <- dbGetQuery(con, "SELECT CAST(x as REAL) as xx FROM ex")
class(res_dbl$xx)
#> [1] "numeric"
res_dbl2 <- dbGetQuery(con, "SELECT CAST(x as DOUBLE) as xx FROM ex")
class(res_dbl2$xx)
#> [1] "numeric"Created on 2018-10-06 by the reprex
package (v0.2.0).
Session info
devtools::session_info()
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