Use ::varchar(max) syntax on Redshift only, support current_schemas()

R/tables.R

@@ -381,18 +381,19 @@ list_fields <- function(conn, id) {
 #' @rdname postgres-tables
 setMethod("dbListObjects", c("PqConnection", "ANY"), function(conn, prefix = NULL, ...) {
   query <- NULL
+  is_redshift <- is(conn, "RedshiftConnection")
+
   if (is.null(prefix)) {
-    if (is(conn, "RedshiftConnection")) {
-      in_current_schema <- "table_schema = current_schema()"
+    if (is_redshift) {
+      null_varchar <- "NULL::varchar(max)"
     } else {
-      in_current_schema <- "(table_schema = ANY(current_schemas(true))) AND (table_schema <> 'pg_catalog')"
+      null_varchar <- "NULL"
     }
     query <- paste0(
-      "SELECT NULL::varchar AS schema, table_name AS table FROM INFORMATION_SCHEMA.tables\n",
-      "WHERE ",
-      in_current_schema, "\n",
+      "SELECT ", null_varchar, " AS schema, table_name AS table FROM INFORMATION_SCHEMA.tables\n",
+      "WHERE (table_schema = ANY(current_schemas(true))) AND (table_schema <> 'pg_catalog')\n",
       "UNION ALL\n",
-      "SELECT DISTINCT table_schema AS schema, NULL::varchar AS table FROM INFORMATION_SCHEMA.tables"
+      "SELECT DISTINCT table_schema AS schema, ", null_varchar, " AS table FROM INFORMATION_SCHEMA.tables"
     )
   } else {
     unquoted <- dbUnquoteIdentifier(conn, prefix)