feat: Connections now inherit from "MySQLConnection" if a MySQL server is detected (server version < 10.0). The new mysql argument to dbConnect() allows overriding the autodetection

NAMESPACE

@@ -27,6 +27,7 @@ export(mariadbHasDefault)
 exportClasses(MariaDBConnection)
 exportClasses(MariaDBDriver)
 exportClasses(MariaDBResult)
+exportClasses(MySQLConnection)
 exportMethods(dbAppendTable)
 exportMethods(dbBegin)
 exportMethods(dbBind)

R/MariaDBConnection.R

@@ -1,11 +1,21 @@
 #' Class MariaDBConnection.
 #'
-#' `MariaDBConnection` objects are usually created by
-#' [DBI::dbConnect()]
+#' `"MariaDBConnection"` objects are usually created by [DBI::dbConnect()].
+#' They represent a connection to a MariaDB or MySQL database.
+#'
+#' The `"MySQLConnection"` class is a subclass of `"MariaDBConnection"`.
+#' Objects of that class are created by `dbConnect(MariaDB(), ..., mysql = TRUE)`
+#' to indicate that the server is a MySQL server.
+#' The \pkg{RMariaDB} package supports both MariaDB and MySQL servers, but the SQL dialect
+#' and other details vary.
+#' The default is to detect the server type based on the version number.
+#'
+#' The older \pkg{RMySQL} package also implements the `"MySQLConnection"` class.
+#' The S4 system is able to distinguish between \pkg{RMariaDB} and \pkg{RMySQL} objects
+#' even if both packages are loaded.
 #'
-#' @export
 #' @keywords internal
-setClass("MariaDBConnection",
+MariaDBConnection <- setClass("MariaDBConnection",
   contains = "DBIConnection",
   slots = list(
     ptr = "externalptr",
@@ -18,6 +28,19 @@ setClass("MariaDBConnection",
   )
 )
 
+#' @exportClass MariaDBConnection
+NULL
+
+#' @keywords internal
+#' @name MariaDBConnection-class
+#' @aliases MySQLConnection-class
+MySQLConnection <- setClass("MySQLConnection",
+  contains = "MariaDBConnection"
+)
+
+#' @exportClass MySQLConnection
+NULL
+
 # format()
 #' @export
 #' @rdname MariaDBConnection-class

R/dbConnect_MariaDBDriver.R

@@ -80,6 +80,12 @@
 #' @param reconnect (experimental) Set to `TRUE` to use `MYSQL_OPT_RECONNECT` to enable
 #'   automatic reconnection. This is experimental and could be dangerous if the connection
 #'   is lost in the middle of a transaction.
+#' @param mysql Set to `TRUE`/`FALSE` to connect to a MySQL server or to a MariaDB server,
+#'   respectively.
+#'   The \pkg{RMariaDB} package supports both MariaDB and MySQL servers, but the SQL dialect
+#'   and other details vary.
+#'   The default is to assume MariaDB if the version is >= 10.0.0, and MySQL otherwise.
+#'
 #' @references
 #' Configuration files: https://mariadb.com/kb/en/library/configuring-mariadb-with-mycnf/
 #' @examples
@@ -108,13 +114,31 @@
 #' }
 #' @usage NULL
 #' @rdname dbConnect-MariaDBDriver-method
-dbConnect_MariaDBDriver <- function(drv, dbname = NULL, username = NULL, password = NULL, host = NULL,
-                                    unix.socket = NULL, port = 0, client.flag = 0,
-                                    groups = "rs-dbi", default.file = NULL, ssl.key = NULL, ssl.cert = NULL,
-                                    ssl.ca = NULL, ssl.capath = NULL, ssl.cipher = NULL, ...,
-                                    load_data_local_infile = FALSE,
-                                    bigint = c("integer64", "integer", "numeric", "character"),
-                                    timeout = 10, timezone = "+00:00", timezone_out = NULL, reconnect = FALSE) {
+dbConnect_MariaDBDriver <- function(
+    drv,
+    dbname = NULL,
+    username = NULL,
+    password = NULL,
+    host = NULL,
+    unix.socket = NULL,
+    port = 0,
+    client.flag = 0,
+    groups = "rs-dbi",
+    default.file = NULL,
+    ssl.key = NULL,
+    ssl.cert = NULL,
+    ssl.ca = NULL,
+    ssl.capath = NULL,
+    ssl.cipher = NULL,
+    ...,
+    load_data_local_infile = FALSE,
+    bigint = c("integer64", "integer", "numeric", "character"),
+    timeout = 10,
+    timezone = "+00:00",
+    timezone_out = NULL,
+    reconnect = FALSE,
+    mysql = NULL) {
+  #
   bigint <- match.arg(bigint)
 
   if (is.infinite(timeout)) {
@@ -157,7 +181,17 @@ dbConnect_MariaDBDriver <- function(drv, dbname = NULL, username = NULL, passwor
 
   info <- connection_info(ptr)
 
-  conn <- new("MariaDBConnection",
+  if (is.null(mysql)) {
+    mysql <- (info$db.version.int < 100000)
+  }
+
+  if (isTRUE(mysql)) {
+    new <- MySQLConnection
+  } else {
+    new <- MariaDBConnection
+  }
+
+  conn <- new(
     ptr = ptr,
     host = info$host,
     db = info$dbname,

R/default.R

@@ -38,7 +38,30 @@ mariadbDefault <- function() {
     },
     error = function(...) {
       testthat::skip("Test database not available")
-    })
+    }
+  )
+}
+
+mysqlDefault <- function() {
+  tryCatch(
+    {
+      mariadb_default(mysql = TRUE)
+    },
+    error = function(...) {
+      testthat::skip("Test database not available")
+    }
+  )
+}
+
+mariadbForceDefault <- function() {
+  tryCatch(
+    {
+      mariadb_default(mysql = FALSE)
+    },
+    error = function(...) {
+      testthat::skip("Test database not available")
+    }
+  )
 }
 
 mariadb_default <- function(...) {
@@ -47,5 +70,8 @@ mariadb_default <- function(...) {
 
 mariadb_default_args <- as.list(c(
   dbname = "test",
+  # host = "192.168.64.2",
+  # user = "compose",
+  # password = "YourStrong!Passw0rd",
   NULL
 ))

src/DbConnection.cpp

@@ -115,6 +115,7 @@ cpp11::list DbConnection::info() {
       "dbname"_nm = std::string(pConn_->db ? pConn_->db : ""),
       "con.type"_nm = std::string(mysql_get_host_info(pConn_)),
       "db.version"_nm = std::string(mysql_get_server_info(pConn_)),
+      "db.version.int"_nm = (int) mysql_get_server_version(pConn_),
       "port"_nm = NA_INTEGER,
       "protocol.version"_nm = (int) mysql_get_proto_info(pConn_),
       "thread.id"_nm = (int) mysql_thread_id(pConn_)

tests/testthat/test-dbConnect.R

@@ -0,0 +1,22 @@
+test_that("Connecting with mysql = FALSE", {
+  con <- mariadbForceDefault()
+  on.exit(dbDisconnect(con))
+
+  expect_s4_class(con, "MariaDBConnection")
+  expect_false(is(con, "MySQLConnection"))
+})
+
+test_that("Connecting with mysql = TRUE", {
+  con <- mysqlDefault()
+  on.exit(dbDisconnect(con))
+
+  expect_s4_class(con, "MariaDBConnection")
+  expect_s4_class(con, "MySQLConnection")
+})
+
+test_that("Connecting with mysql unset", {
+  con <- mariadbDefault()
+  on.exit(dbDisconnect(con))
+
+  expect_s4_class(con, "MariaDBConnection")
+})