fix bug of scan command

src/tendisplus/commands/command_test.cpp

@@ -716,6 +716,63 @@ void testScan(std::shared_ptr<ServerEntry> svr) {
   EXPECT_FALSE(expect.ok());
 }
 
+void testOtherDBScan(std::shared_ptr<ServerEntry> svr) {
+  asio::io_context ioContext;
+  asio::ip::tcp::socket socket(ioContext), socket1(ioContext);
+  NetSession sess(svr, std::move(socket), 1, false, nullptr, nullptr);
+  for (int i = 0; i < 20000; i++) {
+    sess.setArgs({"set", randomStr(10, false), std::to_string(i)});
+    auto expect = Command::runSessionCmd(&sess);
+    EXPECT_TRUE(expect.ok());
+  }
+
+  {
+    sess.setArgs({"select", "15"});
+    auto expect = Command::runSessionCmd(&sess);
+    EXPECT_TRUE(expect.ok());
+    sess.setArgs({"scan", "0"});
+    expect = Command::runSessionCmd(&sess);
+    EXPECT_TRUE(expect.ok());
+    EXPECT_NE(expect.value().find("0"), std::string::npos);
+    EXPECT_NE(expect.value().find("*0"), std::string::npos);
+
+    auto key = randomStr(6, false);
+    sess.setArgs({"set", key, randomStr(10, false)});
+    expect = Command::runSessionCmd(&sess);
+    EXPECT_TRUE(expect.ok());
+
+    sess.setArgs({"scan", "0"});
+    expect = Command::runSessionCmd(&sess);
+    EXPECT_TRUE(expect.ok());
+    EXPECT_NE(expect.value().find("1"), std::string::npos);
+    EXPECT_TRUE(expect.value().find(key) != std::string::npos);
+
+    auto key2 = randomStr(6, false);
+    sess.setArgs({"set", key2, randomStr(10, false)});
+    expect = Command::runSessionCmd(&sess);
+    EXPECT_TRUE(expect.ok());
+
+    sess.setArgs({"scan", "0", "count", "1"});
+    expect = Command::runSessionCmd(&sess);
+    EXPECT_TRUE(expect.ok());
+    EXPECT_NE(expect.value().find("2"), std::string::npos);
+    EXPECT_TRUE((expect.value().find(key) != std::string::npos ||
+                 expect.value().find(key2) != std::string::npos));
+  }
+
+  {
+    sess.setArgs({"select", "4"});
+    auto expect = Command::runSessionCmd(&sess);
+    EXPECT_TRUE(expect.ok());
+
+    sess.setArgs({"scan", "0"});
+    expect = Command::runSessionCmd(&sess);
+    EXPECT_TRUE(expect.ok());
+    EXPECT_NE(expect.value().find("0"), std::string::npos);
+    EXPECT_NE(expect.value().find("*0"), std::string::npos);
+  }
+}
+
 void testMulti(std::shared_ptr<ServerEntry> svr) {
   asio::io_context ioCtx;
   asio::ip::tcp::socket socket(ioCtx), socket1(ioCtx);
@@ -1182,6 +1239,21 @@ TEST(Command, common_scan) {
 #endif
 }
 
+TEST(Command, otherdb_scan) {
+  const auto guard = MakeGuard([] { destroyEnv(); });
+
+  EXPECT_TRUE(setupEnv());
+  auto cfg = makeServerParam();
+  auto server = makeServerEntry(cfg);
+
+  testOtherDBScan(server);
+
+#ifndef _WIN32
+  server->stop();
+  EXPECT_EQ(server.use_count(), 1);
+#endif
+}
+
 TEST(Command, tendisex) {
   const auto guard = MakeGuard([] { destroyEnv(); });
 

src/tendisplus/commands/scan.cpp

@@ -260,8 +260,6 @@ class ZScanbyscoreCommand : public ScanGenericCommand {
     Command::fmtBulk(ss, cursor);
     Command::fmtMultiBulkLen(ss, rcds.size() * 2);
     for (const auto& v : rcds) {
-      auto str = v.toString() + " ";
-      std::cout << str;
       if (v.getRecordKey().getSecondaryKey() ==
           std::to_string(ZSlMetaValue::HEAD_ID)) {
         continue;
@@ -816,7 +814,7 @@ class ScanCommand : public Command {
         // NOTE: no need increase seq. If it meets the criteria,
         //     it must have been increased seq.
         // WARNING: scan this kvstore over no need this record ! ! !
-        if (*scanTimes == scanMaxTimes &&
+        if (*scanTimes == scanMaxTimes && *seq > 0 &&
             expRecord.status().code() != ErrorCodes::ERR_EXHAUST) {
           if (result.empty() || (result.back() != record.getRecordKey())) {
             result.emplace_back(record.getRecordKey());
@@ -841,7 +839,22 @@ class ScanCommand : public Command {
         //     recordType == RecordType::RT_DATA_META) {
         //   (*seq)++;
         // }
-        auto nextSlot = getNextSlot(slots, recordSlotId);
+        // check if we should retain current slot
+        bool retainCurrentSlot = false;
+        // The structure of the UserKey is: SlotID | Type | DBID | PK | 0 | ...
+        // The record located by the seek operation may satisfy the SlotID
+        // condition, but its position could be preceding the target UserKey.
+        // In this case, the current slot must be retained, and the search
+        // should continue until the correct position is found.
+        if (kvstoreSlots.test(recordSlotId)) {
+          retainCurrentSlot =
+            (rt2Char(recordType) < rt2Char(RecordType::RT_DATA_META)) ||
+            (recordType == RecordType::RT_DATA_META && recordDbId < dbId);
+        }
+        // retainCurrentSlot = false, need to seek next slot
+        int32_t nextSlot = !retainCurrentSlot
+          ? getNextSlot(kvstoreSlots, recordSlotId)
+          : recordSlotId;
         // nextSlot == -1 means this kv-store has been iterated over
         if (nextSlot == -1) {
           break;
@@ -853,23 +866,21 @@ class ScanCommand : public Command {
         continue;
       }
 
-      /**
-       * check if this record has expired
-       * expired key shouldn't increase scanTimes,
-       * they only haven't been removed yet.
-       */
-      if (record.getRecordValue().getTtl() > 0 &&
-          record.getRecordValue().getTtl() < msSinceEpoch()) {
-        continue;
-      }
-
       // this record should increase seq.
-      // SLOTS, DBID, TYPE, TTL
+      // SLOTS, DBID, TYPE all match
       // NOTE: lastScanKey has increased seq.
       if (record.getRecordKey() != lastScanRecordKey) {
         (*seq)++;
       }
 
+      // check if this record has expired
+      // expired keys are skipped but still count towards seq (cursor position)
+      // since they occupy a logical position in the database
+      if (record.getRecordValue().getTtl() > 0 &&
+          record.getRecordValue().getTtl() < msSinceEpoch()) {
+        continue;
+      }
+
       // filter
       if (!filter.filter(record)) {
         continue;