fix(kingbase): fallback database list catalog

agents/drivers/kingbase/src/main/java/com/dbx/agent/kingbase/KingbaseAgent.java

@@ -49,21 +49,36 @@ public final class KingbaseAgent extends PostgresLikeAgent {
     @Override
     public List<DatabaseInfo> listDatabases() {
         return unchecked(() -> {
-            String sql = isMysqlCompatMode()
-                ? "SELECT current_database() AS database_name"
-                : "SELECT datname AS database_name FROM sys_database WHERE datistemplate = false ORDER BY datname";
-            try (PreparedStatement stmt = requireConnected().prepareStatement(sql);
-                 ResultSet rs = stmt.executeQuery()) {
-                List<DatabaseInfo> result = new ArrayList<>();
-                while (rs.next()) {
-                    result.add(new DatabaseInfo(rs.getString("database_name")));
-                }
+            if (isMysqlCompatMode()) {
+                List<DatabaseInfo> result = queryDatabases("SELECT current_database() AS database_name");
                 if (!result.isEmpty()) return result;
             }
+            for (String sql : List.of(
+                "SELECT datname AS database_name FROM sys_catalog.sys_database WHERE datistemplate = false ORDER BY datname",
+                "SELECT datname AS database_name FROM pg_database WHERE datistemplate = false ORDER BY datname"
+            )) {
+                try {
+                    List<DatabaseInfo> result = queryDatabases(sql);
+                    if (!result.isEmpty()) return result;
+                } catch (Exception ignored) {
+                    // Kingbase catalog names differ across compatibility modes and versions.
+                }
+            }
             return Collections.singletonList(new DatabaseInfo(getConfiguredDatabase()));
         });
     }
 
+    private List<DatabaseInfo> queryDatabases(String sql) throws Exception {
+        try (PreparedStatement stmt = requireConnected().prepareStatement(sql);
+             ResultSet rs = stmt.executeQuery()) {
+            List<DatabaseInfo> result = new ArrayList<>();
+            while (rs.next()) {
+                result.add(new DatabaseInfo(rs.getString("database_name")));
+            }
+            return result;
+        }
+    }
+
     @Override
     public List<String> listSchemas() {
         return unchecked(() -> {

agents/drivers/kingbase/src/test/java/com/dbx/agent/kingbase/KingbaseAgentTest.java

@@ -19,6 +19,7 @@ import java.lang.reflect.Proxy;
 import java.sql.Connection;
 import java.sql.PreparedStatement;
 import java.sql.ResultSet;
+import java.sql.SQLException;
 import java.sql.Statement;
 import java.sql.Timestamp;
 import java.sql.Types;
@@ -80,7 +81,24 @@ class KingbaseAgentTest extends JdbcFakeExecutionBehaviorTest {
         Assertions.assertEquals(2, databases.size());
         Assertions.assertEquals("app", databases.get(0).getName());
         Assertions.assertEquals("analytics", databases.get(1).getName());
-        Assertions.assertTrue(sql.get(0).contains("FROM sys_database"), sql.get(0));
+        Assertions.assertTrue(sql.get(0).contains("FROM sys_catalog.sys_database"), sql.get(0));
+    }
+
+    @Test
+    void regularListDatabasesFallsBackToPostgresCatalog() {
+        List<String> sql = new ArrayList<>();
+        KingbaseAgent agent = new KingbaseAgent();
+        TestSupport.setPrivateConnection(agent, preparedConnectionWithFailure(sql, "sys_catalog.sys_database", resultSet(
+            new String[]{"database_name"},
+            new Object[][]{{"test"}}
+        )));
+
+        List<DatabaseInfo> databases = agent.listDatabases();
+
+        Assertions.assertEquals(1, databases.size());
+        Assertions.assertEquals("test", databases.get(0).getName());
+        Assertions.assertTrue(sql.get(0).contains("FROM sys_catalog.sys_database"), sql.get(0));
+        Assertions.assertTrue(sql.get(1).contains("FROM pg_database"), sql.get(1));
     }
 
     @Test
@@ -390,6 +408,31 @@ class KingbaseAgentTest extends JdbcFakeExecutionBehaviorTest {
         });
     }
 
+    private static Connection preparedConnectionWithFailure(List<String> sql, String failingSqlFragment, ResultSet fallback) {
+        return proxy(Connection.class, (method, args) -> {
+            if ("prepareStatement".equals(method.getName())) {
+                String preparedSql = String.valueOf(args[0]);
+                sql.add(preparedSql);
+                return proxy(PreparedStatement.class, (statementMethod, statementArgs) -> {
+                    if ("executeQuery".equals(statementMethod.getName())) {
+                        if (preparedSql.contains(failingSqlFragment)) {
+                            throw new SQLException("relation does not exist: " + failingSqlFragment);
+                        }
+                        return fallback;
+                    }
+                    if ("close".equals(statementMethod.getName())) {
+                        return null;
+                    }
+                    return defaultValue(statementMethod.getReturnType());
+                });
+            }
+            if ("isClosed".equals(method.getName())) {
+                return false;
+            }
+            return defaultValue(method.getReturnType());
+        });
+    }
+
     private static ResultSet resultSet(String[] columns, Object[][] rows) {
         int[] index = {-1};
         return proxy(ResultSet.class, (method, args) -> {