Fix SHOW ROLES where there are no roles to display

lurnagao-dahua · Sep 23, 2021 · e38dbf0 · e38dbf0
1 parent 390f2fd
commit e38dbf0
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Showing 3 changed files with 43 additions and 8 deletions.
diff --git a/core/trino-main/src/main/java/io/trino/sql/rewrite/ShowQueriesRewrite.java b/core/trino-main/src/main/java/io/trino/sql/rewrite/ShowQueriesRewrite.java
@@ -120,6 +120,7 @@
 import static io.trino.sql.QueryUtil.aliasedName;
 import static io.trino.sql.QueryUtil.aliasedNullToEmpty;
 import static io.trino.sql.QueryUtil.ascending;
+import static io.trino.sql.QueryUtil.emptyQuery;
 import static io.trino.sql.QueryUtil.equal;
 import static io.trino.sql.QueryUtil.functionCall;
 import static io.trino.sql.QueryUtil.identifier;
@@ -299,18 +300,14 @@ protected Node visitShowRoles(ShowRoles node, Void context)
                 List<Expression> rows = enabledRoles.stream()
                         .map(role -> row(new StringLiteral(role)))
                         .collect(toList());
-                return simpleQuery(
-                        selectList(new AllColumns()),
-                        aliased(new Values(rows), "role_name", ImmutableList.of("Role")));
+                return singleColumnValues(rows, "Role");
             }
             else {
                 accessControl.checkCanShowRoles(session.toSecurityContext(), catalog);
                 List<Expression> rows = metadata.listRoles(session, catalog).stream()
                         .map(role -> row(new StringLiteral(role)))
                         .collect(toList());
-                return simpleQuery(
-                        selectList(new AllColumns()),
-                        aliased(new Values(rows), "role_name", ImmutableList.of("Role")));
+                return singleColumnValues(rows, "Role");
             }
         }
 
@@ -325,10 +322,19 @@ protected Node visitShowRoleGrants(ShowRoleGrants node, Void context)
                     .map(roleGrant -> row(new StringLiteral(roleGrant.getRoleName())))
                     .collect(toList());
 
+            return singleColumnValues(rows, "Role Grants");
+        }
+
+        private Query singleColumnValues(List<Expression> rows, String columnName)
+        {
+            List<String> columns = ImmutableList.of(columnName);
+            if (rows.isEmpty()) {
+                return emptyQuery(columns);
+            }
             return simpleQuery(
                     selectList(new AllColumns()),
-                    aliased(new Values(rows), "role_grants", ImmutableList.of("Role Grants")),
-                    ordering(ascending("Role Grants")));
+                    aliased(new Values(rows), "relation", columns),
+                    ordering(ascending(columnName)));
         }
 
         @Override

diff --git a/core/trino-parser/src/main/java/io/trino/sql/QueryUtil.java b/core/trino-parser/src/main/java/io/trino/sql/QueryUtil.java
@@ -25,6 +25,7 @@
 import io.trino.sql.tree.Identifier;
 import io.trino.sql.tree.LogicalBinaryExpression;
 import io.trino.sql.tree.Node;
+import io.trino.sql.tree.NullLiteral;
 import io.trino.sql.tree.Offset;
 import io.trino.sql.tree.OrderBy;
 import io.trino.sql.tree.QualifiedName;
@@ -267,6 +268,25 @@ public static Query singleValueQuery(String columnName, boolean value)
                 aliased(values, "t", ImmutableList.of(columnName)));
     }
 
+    // TODO pass column types
+    public static Query emptyQuery(List<String> columns)
+    {
+        Select select = selectList(columns.stream()
+                .map(column -> new SingleColumn(new NullLiteral(), QueryUtil.identifier(column)))
+                .toArray(SelectItem[]::new));
+        Optional<Expression> where = Optional.of(FALSE_LITERAL);
+        return query(new QuerySpecification(
+                select,
+                Optional.empty(),
+                where,
+                Optional.empty(),
+                Optional.empty(),
+                ImmutableList.of(),
+                Optional.empty(),
+                Optional.empty(),
+                Optional.empty()));
+    }
+
     public static Query query(QueryBody body)
     {
         return new Query(

diff --git a/testing/trino-tests/src/test/java/io/trino/security/TestAccessControl.java b/testing/trino-tests/src/test/java/io/trino/security/TestAccessControl.java
@@ -411,4 +411,13 @@ public void testNoCatalogIsNeededInSessionForShowRoles()
         assertQuery(session, "SHOW CURRENT ROLES FROM mock", "VALUES 'alice_role'");
         assertQuery(session, "SELECT * FROM mock.information_schema.applicable_roles", "SELECT 'alice', 'USER', 'alice_role', 'NO'");
     }
+
+    @Test
+    public void testEmptyRoles()
+    {
+        assertQueryReturnsEmptyResult("SHOW ROLES");
+        assertQueryReturnsEmptyResult("SHOW ROLE GRANTS");
+        assertQueryReturnsEmptyResult("SHOW CURRENT ROLES");
+        assertQueryReturnsEmptyResult("SELECT * FROM information_schema.applicable_roles");
+    }
 }