Work around missing CAST(x AS INTEGER) in MySQL

tidyverse · Oct 6, 2023 · b84be01 · b84be01
1 parent 62c5eca
commit b84be01
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Showing 2 changed files with 18 additions and 3 deletions.
diff --git a/R/backend-mysql.R b/R/backend-mysql.R
@@ -133,9 +133,24 @@ sql_translation.MariaDBConnection <- function(con) {
 }
 
 #' @export
-sql_translation.MySQL <- sql_translation.MariaDBConnection
+sql_translation.MySQL <- function(con) {
+  maria <- unclass(sql_translation.MariaDBConnection())
+  sql_variant(
+    sql_translator(.parent = maria$scalar,
+      # MySQL doesn't support casting to INTEGER or BIGINT.
+      as.integer = function(x) {
+        sql_expr(TRUNCATE(CAST(!!x %AS% DOUBLE), 0L))
+      },
+      as.integer64 = function(x) {
+        sql_expr(TRUNCATE(CAST(!!x %AS% DOUBLE), 0L))
+      },
+    ),
+    maria$aggregate,
+    maria$window
+  )
+}
 #' @export
-sql_translation.MySQLConnection <- sql_translation.MariaDBConnection
+sql_translation.MySQLConnection <- sql_translation.MySQL
 
 #' @export
 sql_table_analyze.MariaDBConnection <- function(con, table, ...) {

diff --git a/tests/testthat/_snaps/backend-mysql.md b/tests/testthat/_snaps/backend-mysql.md
@@ -64,7 +64,7 @@
     Code
       copy_inline(con_mysql, tibble(x = 1:2, y = letters[1:2])) %>% remote_query()
     Output
-      <SQL> SELECT CAST(`x` AS INTEGER) AS `x`, CAST(`y` AS CHAR) AS `y`
+      <SQL> SELECT TRUNCATE(CAST(`x` AS DOUBLE), 0) AS `x`, CAST(`y` AS CHAR) AS `y`
       FROM (
         SELECT NULL AS `x`, NULL AS `y`
         WHERE (0 = 1)