Fix some tests for random execution order.

Found in MemorySanitizer CI run, by virtue of it running the tests in
random order.

dbms/tests/config/decimals_dictionary.xml

@@ -7,7 +7,7 @@
             <port>9000</port>
             <user>default</user>
             <password></password>
-            <db>test_00950</db>
+            <db>system</db>
             <table>decimals</table>
         </clickhouse>
     </source>
@@ -45,7 +45,7 @@
             <port>9000</port>
             <user>default</user>
             <password></password>
-            <db>test_00950</db>
+            <db>system</db>
             <table>decimals</table>
         </clickhouse>
     </source>
@@ -83,7 +83,7 @@
             <port>9000</port>
             <user>default</user>
             <password></password>
-            <db>test_00950</db>
+            <db>system</db>
             <table>decimals</table>
         </clickhouse>
     </source>
@@ -121,7 +121,7 @@
             <port>9000</port>
             <user>default</user>
             <password></password>
-            <db>test_00950</db>
+            <db>system</db>
             <table>decimals</table>
         </clickhouse>
     </source>
@@ -162,7 +162,7 @@
             <port>9000</port>
             <user>default</user>
             <password></password>
-            <db>test_00950</db>
+            <db>system</db>
             <table>decimals</table>
         </clickhouse>
     </source>

dbms/tests/config/ints_dictionary.xml

@@ -7,7 +7,7 @@
             <port>9000</port>
             <user>default</user>
             <password></password>
-            <db>test_00950</db>
+            <db>system</db>
             <table>ints</table>
         </clickhouse>
     </source>
@@ -70,7 +70,7 @@
             <port>9000</port>
             <user>default</user>
             <password></password>
-            <db>test_00950</db>
+            <db>system</db>
             <table>ints</table>
         </clickhouse>
     </source>
@@ -133,7 +133,7 @@
             <port>9000</port>
             <user>default</user>
             <password></password>
-            <db>test_00950</db>
+            <db>system</db>
             <table>ints</table>
         </clickhouse>
     </source>
@@ -196,7 +196,7 @@
             <port>9000</port>
             <user>default</user>
             <password></password>
-            <db>test_00950</db>
+            <db>system</db>
             <table>ints</table>
         </clickhouse>
     </source>
@@ -259,7 +259,7 @@
             <port>9000</port>
             <user>default</user>
             <password></password>
-            <db>test_00950</db>
+            <db>system</db>
             <table>ints</table>
         </clickhouse>
     </source>
@@ -325,7 +325,7 @@
             <port>9000</port>
             <user>default</user>
             <password></password>
-            <db>test_00950</db>
+            <db>system</db>
             <table>ints</table>
         </clickhouse>
     </source>

dbms/tests/config/strings_dictionary.xml

@@ -7,7 +7,7 @@
             <port>9000</port>
             <user>default</user>
             <password></password>
-            <db>test_00950</db>
+            <db>system</db>
             <table>strings</table>
         </clickhouse>
     </source>
@@ -35,7 +35,7 @@
             <port>9000</port>
             <user>default</user>
             <password></password>
-            <db>test_00950</db>
+            <db>system</db>
             <table>strings</table>
         </clickhouse>
     </source>
@@ -63,7 +63,7 @@
             <port>9000</port>
             <user>default</user>
             <password></password>
-            <db>test_00950</db>
+            <db>system</db>
             <table>strings</table>
         </clickhouse>
     </source>
@@ -91,7 +91,7 @@
             <port>9000</port>
             <user>default</user>
             <password></password>
-            <db>test_00950</db>
+            <db>system</db>
             <table>strings</table>
         </clickhouse>
     </source>
@@ -122,7 +122,7 @@
             <port>9000</port>
             <user>default</user>
             <password></password>
-            <db>test_00950</db>
+            <db>system</db>
             <table>strings</table>
         </clickhouse>
     </source>
@@ -153,7 +153,7 @@
             <port>9000</port>
             <user>default</user>
             <password></password>
-            <db>test_00950</db>
+            <db>system</db>
             <table>strings</table>
         </clickhouse>
     </source>
@@ -184,7 +184,7 @@
             <port>9000</port>
             <user>default</user>
             <password></password>
-            <db>test_00950</db>
+            <db>system</db>
             <table>strings</table>
         </clickhouse>
     </source>

dbms/tests/queries/0_stateless/00950_dict_get.sql

@@ -1,6 +1,5 @@
--- Must use `test_00950` database and these tables - they're configured in dbms/tests/*_dictionary.xml
+-- Must use `system` database and these tables - they're configured in dbms/tests/*_dictionary.xml
-create database if not exists test_00950;
+use system;
-use test_00950;
 drop table if exists ints;
 drop table if exists strings;
 drop table if exists decimals;
@@ -270,7 +269,14 @@ select 'dictGetOrDefault', 'complex_cache_decimals' as dict_name, tuple(toUInt64
     dictGetOrDefault(dict_name, 'd64', k, toDecimal64(42, 6)),
     dictGetOrDefault(dict_name, 'd128', k, toDecimal128(42, 1));
 
-drop table ints;
+--
-drop table strings;
+-- Keep the tables, so that the dictionaries can be reloaded correctly and
-drop table decimals;
+-- SYSTEM RELOAD DICTIONARIES doesn't break.
-drop database test_00950;
+-- We could also:
+-- * drop the dictionaries -- not possible, they are configured in a .xml;
+-- * switch dictionaries to DDL syntax so that they can be dropped -- tedious,
+--   because there are a couple dozens of them, and also we need to have some
+--   .xml dictionaries in tests so that we test backward compatibility with this
+--   format;
+-- * unload dictionaries -- no command for that.
+--