[CSV] Avoid expensive call to fetch DB metadata (#31556)

* Avoid expensive call to fetch DB metadata

Double-checking the schema name is unnecessarily defensive since we
already call include-schema?

* Check that schema is set

src/metabase/api/card.clj

@@ -49,7 +49,6 @@
    [metabase.server.middleware.offset-paging :as mw.offset-paging]
    [metabase.sync :as sync]
    [metabase.sync.analyze.query-results :as qr]
-   [metabase.sync.fetch-metadata :as fetch-metadata]
    [metabase.sync.sync-metadata.fields :as sync-fields]
    [metabase.sync.sync-metadata.tables :as sync-tables]
    [metabase.task.persist-refresh :as task.persist-refresh]
@@ -1168,6 +1167,10 @@ saved later when it is ready."
           _check_perms      (api/check-403 (mi/can-read? database))
           driver            (driver.u/database->driver database)
           schema-name       (public-settings/uploads-schema-name)
+          _check-schema     (when (and (str/blank? schema-name)
+                                       (driver/database-supports? driver :schemas database))
+                              (throw (ex-info (tru "A schema has not been set.")
+                                              {:status-code 422})))
           _check-schema     (when-not (or (nil? schema-name)
                                           (driver.s/include-schema? database schema-name))
                               (throw (ex-info (tru "The schema {0} is not syncable." schema-name)
@@ -1184,14 +1187,7 @@ saved later when it is ready."
                               (str schema-name "." table-name))
           stats             (upload/load-from-csv driver db-id schema+table-name csv-file)
           ;; Syncs are needed immediately to create the Table and its Fields; the scan is settings-dependent and can be async
-          table-metadata    (first (filter (fn [{:keys [name]}] (= (u/lower-case-en name) table-name))
-                                           (:tables (fetch-metadata/db-metadata database))))
-          actual-schema     (:schema table-metadata)
-          _                 (when (nil? table-metadata)
-                              (driver/drop-table driver db-id table-name)
-                              (throw (ex-info (tru "The CSV file was uploaded to {0}, but the table could not be created or found." schema+table-name)
-                                              {:status-code 422})))
-          table             (sync-tables/create-or-reactivate-table! database {:name table-name :schema actual-schema})
+          table             (sync-tables/create-or-reactivate-table! database {:name table-name :schema (not-empty schema-name)})
           _sync             (scan-and-sync-table! database table)
           card              (create-card!
                              {:collection_id          collection-id,

test/metabase/api/card_test.clj

@@ -2879,14 +2879,20 @@
                                              uploads-database-id  db-id
                                              uploads-schema-name  nil
                                              uploads-table-prefix "uploaded_magic_"]
-            (let [new-model (upload-example-csv! nil)
-                  new-table (t2/select-one Table :db_id db-id)]
-              (is (= "Example Csv File" (:name new-model)))
-              (is (=? {:name #"(?i)uploaded_magic_example(.*)"}
-                      new-table))
-              (if (= driver/*driver* :mysql)
-                (is (nil? (:schema new-table)))
-                (is (=? {:schema #"(?i)public"} new-table))))))))))
+            (if (= driver/*driver* :mysql)
+              (let [new-model (upload-example-csv! nil)
+                    new-table (t2/select-one Table :db_id db-id)]
+                (is (= "Example Csv File" (:name new-model)))
+                (is (=? {:name #"(?i)uploaded_magic_example(.*)"}
+                        new-table))
+                (if (= driver/*driver* :mysql)
+                  (is (nil? (:schema new-table)))
+                  (is (=? {:schema #"(?i)public"} new-table))))
+              ;; Else, for drivers that support schemas
+              (is (thrown-with-msg?
+                   java.lang.Exception
+                   #"^A schema has not been set."
+                   (upload-example-csv! nil))))))))))
 
 (deftest upload-csv!-failure-test
   ;; Just test with postgres because failure should be independent of the driver