address as.double() and as.character() errors with Teradata (#1545)

--------- Co-authored-by: simonpcouch <[email protected]>
tidyverse · Oct 24, 2024 · 7fb52d7 · 7fb52d7
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Showing 3 changed files with 12 additions and 4 deletions.
diff --git a/NEWS.md b/NEWS.md
@@ -1,5 +1,8 @@
 # dbplyr (development version)
 
+* Translations for `as.double()` and `as.character()` with Teradata previously
+  raised errors and are now correct (@rplsmn, #1545).
+
 * Translations of `difftime()` for Postgres, SQL server, Redshift, and Snowflake
   previously returned the wrong sign and are now correct (@edward-burn, #1532). 
 

diff --git a/R/backend-teradata.R b/R/backend-teradata.R
@@ -109,8 +109,12 @@ sql_translation.Teradata <- function(con) {
                         digits <- vctrs::vec_cast(digits, integer())
                         sql_expr(CAST(!!x %as% DECIMAL(12L, !!digits)))
                       },
-      as.double     = sql_cast("NUMERIC"),
-      as.character  = sql_cast("VARCHAR(MAX)"),
+      as.double     = sql_cast("FLOAT"),
+      as.character  = function(x, nchar = 255L) {
+        check_number_whole(nchar, min = 0, max = 64000)
+        nchar <- vctrs::vec_cast(nchar, integer())
+        sql_expr(CAST(!!x %as% VARCHAR(!!nchar)))
+      },
       as.Date       = teradata_as_date,
       log10         = sql_prefix("LOG"),
       log           = sql_log(),

diff --git a/tests/testthat/test-backend-teradata.R b/tests/testthat/test-backend-teradata.R
@@ -4,8 +4,9 @@ test_that("custom scalar translated correctly", {
   expect_equal(test_translate_sql(x != y),          sql("`x` <> `y`"))
   expect_equal(test_translate_sql(as.numeric(x)),   sql("CAST(`x` AS DECIMAL(12, 9))"))
   expect_equal(test_translate_sql(as.numeric(x, 8)),   sql("CAST(`x` AS DECIMAL(12, 8))"))
-  expect_equal(test_translate_sql(as.double(x)),    sql("CAST(`x` AS NUMERIC)"))
-  expect_equal(test_translate_sql(as.character(x)), sql("CAST(`x` AS VARCHAR(MAX))"))
+  expect_equal(test_translate_sql(as.double(x)),    sql("CAST(`x` AS FLOAT)"))
+  expect_equal(test_translate_sql(as.character(x)), sql("CAST(`x` AS VARCHAR(255))"))
+  expect_equal(test_translate_sql(as.character(x, 12)), sql("CAST(`x` AS VARCHAR(12))"))
   expect_equal(test_translate_sql(log(x)),          sql("LN(`x`)"))
   expect_equal(test_translate_sql(cot(x)),          sql("1 / TAN(`x`)"))
   expect_equal(test_translate_sql(nchar(x)),        sql("CHARACTER_LENGTH(`x`)"))