Add `schemas` driver feature (#30536)

* Add schemas driver feature flag

* Add sql_jdbc schemas test

* Add more general test

* Make schemas feature default to true

* Implement supports? for other drivers

* Add feature to the driver changelog

* Remove redundant schemas from h2

* Spelling fix

Pre-rebase SHA: 8a2c7e0 or 5686b2f

* MySQL does *not* support schemas

* Bad rebase

* Typo?

Co-Authored-By: Tim Macdonald <tim@metabase.com>

docs/developers-guide/driver-changelog.md

@@ -6,12 +6,17 @@ title: Driver interface changelog
 
 ## Metabase 0.47.0
 
-- The multimethod `metabase.driver/syncable-schemas` has been added. This method is used to list schemas to upload 
+- The multimethod `metabase.driver/syncable-schemas` has been added. This method is used to list schemas to upload
   CSVs to, and it should include all schemas that are able to be synced to. Currently it only needs to be implemented
   if the database has schema, and the database supports the `uploads` feature.
 
+- A new driver feature has been added: `:schemas`. This feature signals whether the database organizes tables in
+  schemas (also known as namespaces) or not. Most databases have schemas so this feature is supported on by default.
+  An implemention of the multimethod `metabase.driver/database-supports?` for `:schemas` is required only if the
+  database doesn't store tables in schemas.
+
 - The multimethod `metabase.driver/supports?` has been deprecated in favor of `metabase.driver/database-supports?`. The existing default implementation of `database-supports?` currently calls `supports?`, but it will be removed in 0.55.0.
-  
+
 ## Metabase 0.46.0
 
 - The process for building a driver has changed slightly in Metabase 0.46.0. Your build command should now look

modules/drivers/mongo/src/metabase/driver/mongo.clj

@@ -270,6 +270,8 @@
 (when-not (get (methods driver/supports?) [:mongo :foreign-keys])
   (defmethod driver/supports? [:mongo :foreign-keys] [_ _] true))
 
+(defmethod driver/database-supports? [:mongo :schemas] [_driver _feat _db] false)
+
 (defmethod driver/database-supports? [:mongo :expressions]
   [_driver _feature db]
   (-> (:dbms_version db)

modules/drivers/sqlite/src/metabase/driver/sqlite.clj

@@ -38,6 +38,7 @@
                               :percentile-aggregations                false
                               :advanced-math-expressions              false
                               :standard-deviation-aggregations        false
+                              :schemas                                false
                               :datetime-diff                          true
                               :now                                    true
                               ;; SQLite `LIKE` clauses are case-insensitive by default, and thus cannot be made case-sensitive. So let people know

src/metabase/driver.clj

@@ -493,6 +493,10 @@
     ;; Does the driver support uploading files
     :uploads
 
+    ;; Does the driver support schemas (aka namespaces) for tables
+    ;; DEFAULTS TO TRUE
+    :schemas
+
     ;; Does the driver support custom writeback actions. Drivers that support this must
     ;; implement [[execute-write-query!]]
     :actions/custom
@@ -516,6 +520,8 @@
 
 (defmethod supports? :default [_ _] false)
 
+(defmethod supports? [::driver :schemas] [_ _] true)
+
 (defmulti database-supports?
   "Does this driver and specific instance of a database support a certain `feature`?
   (A feature is a keyword, and can be any of the ones listed above in `driver-features`.

src/metabase/driver/mysql.clj

@@ -57,6 +57,7 @@
                               :percentile-aggregations false
                               :full-join               false
                               :uploads                 true
+                              :schemas                 false
                               ;; MySQL LIKE clauses are case-sensitive or not based on whether the collation of the server and the columns
                               ;; themselves. Since this isn't something we can really change in the query itself don't present the option to the
                               ;; users in the UI

src/metabase/driver/postgres.clj

@@ -47,10 +47,11 @@
 
 (driver/register! :postgres, :parent :sql-jdbc)
 
-(doseq [[feature supported?] {:datetime-diff true
-                              :persist-models true
-                              :convert-timezone true
-                              :now true}]
+(doseq [[feature supported?] {:convert-timezone true
+                              :datetime-diff    true
+                              :now              true
+                              :persist-models   true
+                              :schemas          true}]
   (defmethod driver/database-supports? [:postgres feature] [_driver _feature _db] supported?))
 
 (defmethod driver/database-supports? [:postgres :nested-field-columns]

test/metabase/driver_test.clj

@@ -4,6 +4,7 @@
    [metabase.driver :as driver]
    [metabase.driver.impl :as driver.impl]
    [metabase.plugins.classloader :as classloader]
+   [metabase.test :as mt]
    [metabase.test.data.env :as tx.env]))
 
 (set! *warn-on-reflection* true)
@@ -53,3 +54,15 @@
                                                                       props-by-name)
                                                               vec
                                                               pr-str)))))))
+
+(deftest supports-schemas-matches-describe-database-test
+  (mt/test-drivers (mt/normal-drivers)
+    (if (driver/database-supports? driver/*driver* :schemas (mt/db))
+      (testing "`describe-database` should return schemas with tables if the database supports schemas"
+        (is (some? (->> (driver/describe-database driver/*driver* (mt/db))
+                        :tables
+                        (some :schema)))))
+      (testing "`describe-database` should not return schemas with tables if the database doesn't support schemas"
+        (is (nil? (->> (driver/describe-database driver/*driver* (mt/db))
+                       :tables
+                       (some :schema))))))))