Document db_col_types()

NAMESPACE

@@ -32,6 +32,9 @@ S3method(cross_join,tbl_lazy)
 S3method(db_analyze,DBIConnection)
 S3method(db_col_types,DBIConnection)
 S3method(db_col_types,MariaDBConnection)
+S3method(db_col_types,MySQL)
+S3method(db_col_types,MySQLConnection)
+S3method(db_col_types,PostgreSQL)
 S3method(db_col_types,PqConnection)
 S3method(db_col_types,TestConnection)
 S3method(db_collect,DBIConnection)

R/backend-mysql.R

@@ -50,6 +50,17 @@ db_connection_describe.MySQL <- db_connection_describe.MariaDBConnection
 #' @export
 db_connection_describe.MySQLConnection <- db_connection_describe.MariaDBConnection
 
+#' @export
+db_col_types.MariaDBConnection <- function(con, table, call) {
+  table <- as_table_ident(table, error_call = call)
+  col_info_df <- DBI::dbGetQuery(con, glue_sql2(con, "SHOW COLUMNS FROM {.tbl table};"))
+  set_names(col_info_df[["Type"]], col_info_df[["Field"]])
+}
+#' @export
+db_col_types.MySQL <- db_col_types.MariaDBConnection
+#' @export
+db_col_types.MySQLConnection <- db_col_types.MariaDBConnection
+
 #' @export
 sql_translation.MariaDBConnection <- function(con) {
   sql_variant(

R/backend-postgres.R

@@ -404,4 +404,17 @@ db_supports_table_alias_with_as.PostgreSQL <- function(con) {
   TRUE
 }
 
+#' @export
+db_col_types.PqConnection <- function(con, table, call) {
+  table <- as_table_ident(table, error_call = call)
+  res <- DBI::dbSendQuery(con, glue_sql2(con, "SELECT * FROM {.tbl table} LIMIT 0"))
+  on.exit(DBI::dbClearResult(res))
+  DBI::dbFetch(res, n = 0)
+  col_info_df <- DBI::dbColumnInfo(res)
+  set_names(col_info_df[[".typname"]], col_info_df[["name"]])
+}
+
+#' @export
+db_col_types.PostgreSQL <- db_col_types.PqConnection
+
 utils::globalVariables(c("strpos", "%::%", "%FROM%", "%ILIKE%", "DATE", "EXTRACT", "TO_CHAR", "string_agg", "%~*%", "%~%", "MONTH", "DOY", "DATE_TRUNC", "INTERVAL", "FLOOR", "WEEK"))

R/db.R

@@ -7,6 +7,8 @@
 #' * `dbplyr_edition()` declares which version of the dbplyr API you want.
 #'    See below for more details.
 #'
+#' * `db_col_types()` returns the column types of a table.
+#'
 #' @section dbplyr 2.0.0:
 #' dbplyr 2.0.0 renamed a number of generics so that they could be cleanly moved
 #' from dplyr to dbplyr. If you have an existing backend, you'll need to rename
@@ -80,6 +82,26 @@ db_sql_render.DBIConnection <- function(con, sql, ..., cte = FALSE, sql_options
   sql_render(sql, con = con, ..., sql_options = sql_options)
 }
 
+#' @rdname db-misc
+#' @export
+db_col_types <- function(con, table, call) {
+  if (is_null(table)) {
+    return(NULL)
+  }
+
+  UseMethod("db_col_types")
+}
+
+#' @export
+db_col_types.TestConnection <- function(con, table, call) {
+  NULL
+}
+
+#' @export
+db_col_types.DBIConnection <- function(con, table, call) {
+  NULL
+}
+
 #' Options for generating SQL
 #'
 #' @param cte If `FALSE`, the default, subqueries are used. If `TRUE` common

R/rows.R

@@ -758,42 +758,6 @@ rows_auto_copy <- function(x, y, copy, call = caller_env()) {
   auto_copy(x, y, copy = copy, types = x_types)
 }
 
-#' @export
-db_col_types <- function(con, table, call) {
-  if (is_null(table)) {
-    return(NULL)
-  }
-
-  UseMethod("db_col_types")
-}
-
-#' @export
-db_col_types.TestConnection <- function(con, table, call) {
-  NULL
-}
-
-#' @export
-db_col_types.DBIConnection <- function(con, table, call) {
-  NULL
-}
-
-#' @export
-db_col_types.PqConnection <- function(con, table, call) {
-  table <- as_table_ident(table, error_call = call)
-  res <- DBI::dbSendQuery(con, glue_sql2(con, "SELECT * FROM {.tbl table} LIMIT 0"))
-  on.exit(DBI::dbClearResult(res))
-  DBI::dbFetch(res, n = 0)
-  col_info_df <- DBI::dbColumnInfo(res)
-  set_names(col_info_df[[".typname"]], col_info_df[["name"]])
-}
-
-#' @export
-db_col_types.MariaDBConnection <- function(con, table, call) {
-  table <- as_table_ident(table, error_call = call)
-  col_info_df <- DBI::dbGetQuery(con, glue_sql2(con, "SHOW COLUMNS FROM {.tbl table};"))
-  set_names(col_info_df[["Type"]], col_info_df[["Field"]])
-}
-
 rows_get_or_execute <- function(x, sql, returning_cols, call = caller_env()) {
   con <- remote_con(x)
   msg <- "Can't modify database table {.val {remote_name(x)}}."