mysql-proxy: skip admin for no-FROM multi-expression selects; add tests

Author: nunotabashinobu066-cmd

proxy/backend/dialect/mysql/src/main/java/org/apache/shardingsphere/proxy/backend/mysql/handler/admin/factory/withoutfrom/MySQLSelectWithoutFromAdminExecutorFactory.java

@@ -93,9 +93,17 @@ private static Optional<DatabaseAdminExecutor> mockExecutor(final SelectStatemen
             return Optional.of(new NoResourceShowExecutor(sqlStatement));
         }
         boolean isUseDatabase = null != databaseName || sqlStatement.getFrom().isPresent();
+        if (!isUseDatabase && isMultiExpressionSelect(sqlStatement)) {
+            return Optional.empty();
+        }
         return isUseDatabase ? Optional.empty() : Optional.of(new UnicastResourceShowExecutor(sqlStatement, sql));
     }
 
+    private static boolean isMultiExpressionSelect(final SelectStatement sqlStatement) {
+        Collection<ProjectionSegment> projections = sqlStatement.getProjections().getProjections();
+        return projections.size() > 1;
+    }
+    
     private static boolean isEmptyResource(final ShardingSphereMetaData metaData) {
         Collection<ShardingSphereDatabase> databases = metaData.getAllDatabases();
         return databases.isEmpty() || databases.stream().noneMatch(ShardingSphereDatabase::containsDataSource);

proxy/backend/dialect/mysql/src/test/java/org/apache/shardingsphere/proxy/backend/mysql/handler/admin/MySQLAdminExecutorCreatorTest.java

@@ -73,6 +73,7 @@
 import org.junit.jupiter.api.Test;
 import org.junit.jupiter.api.extension.ExtendWith;
 
+import java.util.Arrays;
 import java.util.Collection;
 import java.util.Collections;
 import java.util.Optional;
@@ -405,4 +406,49 @@ void assertCreateWithDMLStatement() {
         Optional<DatabaseAdminExecutor> actual = new MySQLAdminExecutorCreator().create(sqlStatementContext, "DELETE FROM t", "", Collections.emptyList());
         assertThat(actual, is(Optional.empty()));
     }
+    
+    @Test
+    void assertCreateWithNoFromAndMultiProjectionsSkipsAdmin() {
+        ResourceMetaData resourceMetaData = new ResourceMetaData(Collections.singletonMap("ds_0", new MockedDataSource()));
+        ShardingSphereDatabase database = new ShardingSphereDatabase("db_0", databaseType, resourceMetaData, mock(RuleMetaData.class), Collections.emptyList());
+        initProxyContext(Collections.singleton(database));
+        
+        SelectStatement selectStatement = mock(SelectStatement.class);
+        when(selectStatement.getFrom()).thenReturn(Optional.empty());
+        ProjectionsSegment projectionsSegment = mock(ProjectionsSegment.class);
+        when(projectionsSegment.getProjections()).thenReturn(Arrays.asList(
+                new ExpressionProjectionSegment(0, 10, "database()"),
+                new ExpressionProjectionSegment(0, 10, "schema()"),
+                new ExpressionProjectionSegment(0, 10, "left(user(),instr(concat(user(),'@'),'@')-1)")));
+        when(selectStatement.getProjections()).thenReturn(projectionsSegment);
+        SelectStatementContext sqlStatementContext = mock(SelectStatementContext.class);
+        when(sqlStatementContext.getSqlStatement()).thenReturn(selectStatement);
+        
+        Optional<DatabaseAdminExecutor> actual =
+                new MySQLAdminExecutorCreator().create(sqlStatementContext, "SELECT database(),schema(),left(user(),instr(concat(user(),'@'),'@')-1)", null, Collections.emptyList());
+        assertThat(actual, is(Optional.empty()));
+    }
+
+    @Test
+    void assertCreateWithMultiSystemVariablesUseSysVarExecutor() {
+        initProxyContext(Collections.emptyList());
+        SelectStatement selectStatement = mock(SelectStatement.class);
+        when(selectStatement.getFrom()).thenReturn(Optional.empty());
+        ProjectionsSegment projectionsSegment = mock(ProjectionsSegment.class);
+        VariableSegment v1 = new VariableSegment(0, 0, "version", "SESSION");
+        VariableSegment v2 = new VariableSegment(0, 0, "transaction_isolation", "SESSION");
+        when(projectionsSegment.getProjections()).thenReturn(Arrays.asList(
+                new ExpressionProjectionSegment(0, 10, "@@session.version", v1),
+                new ExpressionProjectionSegment(0, 10, "@@session.transaction_isolation", v2)
+        ));
+        when(selectStatement.getProjections()).thenReturn(projectionsSegment);
+
+        SelectStatementContext sqlStatementContext = mock(SelectStatementContext.class);
+        when(sqlStatementContext.getSqlStatement()).thenReturn(selectStatement);
+
+        Optional<DatabaseAdminExecutor> actual = new MySQLAdminExecutorCreator().create(
+                sqlStatementContext, "SELECT @@session.version, @@session.transaction_isolation", null, Collections.emptyList());
+        assertTrue(actual.isPresent());
+        assertThat(actual.get(), isA(MySQLSystemVariableQueryExecutor.class));
+    }
 }