[test](read-uncommitted) Add unit and regression tests for UncommittedRowsetRegistry

BE unit tests cover register/get/unregister/expiration/sharding logic.
Regression test verifies session variable, queries on dup/mow/mor tables,
isolation level switching, and predicate pushdown under READ-UNCOMMITTED.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: dataroaring

be/test/olap/uncommitted_rowset_registry_test.cpp

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+// Licensed to the Apache Software Foundation (ASF) under one
+// or more contributor license agreements.  See the NOTICE file
+// distributed with this work for additional information
+// regarding copyright ownership.  The ASF licenses this file
+// to you under the Apache License, Version 2.0 (the
+// "License"); you may not use this file except in compliance
+// with the License.  You may obtain a copy of the License at
+//
+//   http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing,
+// software distributed under the License is distributed on an
+// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+// KIND, either express or implied.  See the License for the
+// specific language governing permissions and limitations
+// under the License.
+
+#include "olap/uncommitted_rowset_registry.h"
+
+#include <gtest/gtest.h>
+
+#include <memory>
+#include <vector>
+
+#include "common/config.h"
+#include "olap/rowset/rowset_meta.h"
+#include "olap/tablet_schema.h"
+#include "testutil/mock_rowset.h"
+
+namespace doris {
+
+class UncommittedRowsetRegistryTest : public testing::Test {
+protected:
+    // Helper: create a MockRowset with a unique RowsetId.
+    static RowsetSharedPtr create_mock_rowset(int64_t id_high) {
+        auto schema = std::make_shared<TabletSchema>();
+        auto rs_meta = std::make_shared<RowsetMeta>();
+        RowsetId rid;
+        rid.init(id_high);
+        rs_meta->set_rowset_id(rid);
+        rs_meta->set_rowset_type(BETA_ROWSET);
+        RowsetSharedPtr rowset;
+        EXPECT_EQ(Status::OK(), MockRowset::create_rowset(schema, rs_meta, &rowset));
+        return rowset;
+    }
+
+    // Helper: create an UncommittedRowsetEntry with the given fields.
+    static std::shared_ptr<UncommittedRowsetEntry> make_entry(int64_t tablet_id, int64_t txn_id,
+                                                              int64_t id_high) {
+        auto entry = std::make_shared<UncommittedRowsetEntry>();
+        entry->rowset = create_mock_rowset(id_high);
+        entry->transaction_id = txn_id;
+        entry->partition_id = 1;
+        entry->tablet_id = tablet_id;
+        entry->register_time_ms = 0; // will be overwritten by register_rowset
+        return entry;
+    }
+};
+
+TEST_F(UncommittedRowsetRegistryTest, RegisterAndGet) {
+    UncommittedRowsetRegistry registry;
+
+    auto entry = make_entry(/*tablet_id=*/100, /*txn_id=*/1, /*id_high=*/1);
+    registry.register_rowset(entry);
+
+    std::vector<std::shared_ptr<UncommittedRowsetEntry>> result;
+    registry.get_uncommitted_rowsets(100, &result);
+
+    ASSERT_EQ(result.size(), 1);
+    EXPECT_EQ(result[0]->tablet_id, 100);
+    EXPECT_EQ(result[0]->transaction_id, 1);
+    EXPECT_GT(result[0]->register_time_ms, 0);
+}
+
+TEST_F(UncommittedRowsetRegistryTest, GetEmpty) {
+    UncommittedRowsetRegistry registry;
+
+    std::vector<std::shared_ptr<UncommittedRowsetEntry>> result;
+    registry.get_uncommitted_rowsets(999, &result);
+
+    EXPECT_TRUE(result.empty());
+}
+
+TEST_F(UncommittedRowsetRegistryTest, MultipleTabletsIsolation) {
+    UncommittedRowsetRegistry registry;
+
+    registry.register_rowset(make_entry(100, 1, 1));
+    registry.register_rowset(make_entry(200, 2, 2));
+
+    std::vector<std::shared_ptr<UncommittedRowsetEntry>> result100;
+    registry.get_uncommitted_rowsets(100, &result100);
+    ASSERT_EQ(result100.size(), 1);
+    EXPECT_EQ(result100[0]->transaction_id, 1);
+
+    std::vector<std::shared_ptr<UncommittedRowsetEntry>> result200;
+    registry.get_uncommitted_rowsets(200, &result200);
+    ASSERT_EQ(result200.size(), 1);
+    EXPECT_EQ(result200[0]->transaction_id, 2);
+}
+
+TEST_F(UncommittedRowsetRegistryTest, MultipleEntriesSameTablet) {
+    UncommittedRowsetRegistry registry;
+
+    registry.register_rowset(make_entry(100, 10, 10));
+    registry.register_rowset(make_entry(100, 20, 20));
+    registry.register_rowset(make_entry(100, 30, 30));
+
+    std::vector<std::shared_ptr<UncommittedRowsetEntry>> result;
+    registry.get_uncommitted_rowsets(100, &result);
+
+    ASSERT_EQ(result.size(), 3);
+    // Verify all three transaction IDs are present
+    std::set<int64_t> txn_ids;
+    for (const auto& e : result) {
+        txn_ids.insert(e->transaction_id);
+    }
+    EXPECT_TRUE(txn_ids.count(10));
+    EXPECT_TRUE(txn_ids.count(20));
+    EXPECT_TRUE(txn_ids.count(30));
+}
+
+TEST_F(UncommittedRowsetRegistryTest, UnregisterByTxnId) {
+    UncommittedRowsetRegistry registry;
+
+    registry.register_rowset(make_entry(100, 1, 1));
+
+    // Verify it exists
+    std::vector<std::shared_ptr<UncommittedRowsetEntry>> result;
+    registry.get_uncommitted_rowsets(100, &result);
+    ASSERT_EQ(result.size(), 1);
+
+    // Unregister
+    registry.unregister_rowset(100, 1);
+
+    result.clear();
+    registry.get_uncommitted_rowsets(100, &result);
+    EXPECT_TRUE(result.empty());
+}
+
+TEST_F(UncommittedRowsetRegistryTest, UnregisterNonexistent) {
+    UncommittedRowsetRegistry registry;
+
+    // Should not crash or throw on empty registry
+    registry.unregister_rowset(999, 1);
+
+    // Register something, then unregister a non-existent txn_id
+    registry.register_rowset(make_entry(100, 1, 1));
+    registry.unregister_rowset(100, 999);
+
+    // Original entry should still be present
+    std::vector<std::shared_ptr<UncommittedRowsetEntry>> result;
+    registry.get_uncommitted_rowsets(100, &result);
+    ASSERT_EQ(result.size(), 1);
+    EXPECT_EQ(result[0]->transaction_id, 1);
+}
+
+TEST_F(UncommittedRowsetRegistryTest, UnregisterLeavesOtherEntries) {
+    UncommittedRowsetRegistry registry;
+
+    registry.register_rowset(make_entry(100, 1, 1));
+    registry.register_rowset(make_entry(100, 2, 2));
+
+    registry.unregister_rowset(100, 1);
+
+    std::vector<std::shared_ptr<UncommittedRowsetEntry>> result;
+    registry.get_uncommitted_rowsets(100, &result);
+    ASSERT_EQ(result.size(), 1);
+    EXPECT_EQ(result[0]->transaction_id, 2);
+}
+
+TEST_F(UncommittedRowsetRegistryTest, RemoveExpiredEntries) {
+    UncommittedRowsetRegistry registry;
+
+    // Save and override the config
+    int32_t saved_expire = config::uncommitted_rowset_expire_sec;
+    config::uncommitted_rowset_expire_sec = 60; // 60 seconds
+
+    // Register two entries
+    auto entry_old = make_entry(100, 1, 1);
+    auto entry_fresh = make_entry(100, 2, 2);
+    registry.register_rowset(entry_old);
+    registry.register_rowset(entry_fresh);
+
+    // Simulate: make entry_old look like it was registered 120 seconds ago
+    entry_old->register_time_ms -= 120 * 1000L;
+
+    registry.remove_expired_entries();
+
+    std::vector<std::shared_ptr<UncommittedRowsetEntry>> result;
+    registry.get_uncommitted_rowsets(100, &result);
+    ASSERT_EQ(result.size(), 1);
+    EXPECT_EQ(result[0]->transaction_id, 2);
+
+    // Restore config
+    config::uncommitted_rowset_expire_sec = saved_expire;
+}
+
+TEST_F(UncommittedRowsetRegistryTest, ShardingDistribution) {
+    UncommittedRowsetRegistry registry;
+
+    // Tablets 0 and 16 both map to shard 0 (0 % 16 == 16 % 16 == 0).
+    // They should still be isolated by tablet_id in the shard's map.
+    registry.register_rowset(make_entry(0, 1, 1));
+    registry.register_rowset(make_entry(16, 2, 2));
+
+    std::vector<std::shared_ptr<UncommittedRowsetEntry>> result0;
+    registry.get_uncommitted_rowsets(0, &result0);
+    ASSERT_EQ(result0.size(), 1);
+    EXPECT_EQ(result0[0]->transaction_id, 1);
+
+    std::vector<std::shared_ptr<UncommittedRowsetEntry>> result16;
+    registry.get_uncommitted_rowsets(16, &result16);
+    ASSERT_EQ(result16.size(), 1);
+    EXPECT_EQ(result16[0]->transaction_id, 2);
+
+    // Tablets 1 and 2 map to different shards (1 % 16 != 2 % 16).
+    // Basic correctness check for different-shard tablets.
+    registry.register_rowset(make_entry(1, 3, 3));
+    registry.register_rowset(make_entry(2, 4, 4));
+
+    std::vector<std::shared_ptr<UncommittedRowsetEntry>> result1;
+    registry.get_uncommitted_rowsets(1, &result1);
+    ASSERT_EQ(result1.size(), 1);
+    EXPECT_EQ(result1[0]->transaction_id, 3);
+
+    std::vector<std::shared_ptr<UncommittedRowsetEntry>> result2;
+    registry.get_uncommitted_rowsets(2, &result2);
+    ASSERT_EQ(result2.size(), 1);
+    EXPECT_EQ(result2[0]->transaction_id, 4);
+}
+
+} // namespace doris