GH-3442: Fix MySQL/MariaDB message ordering in JdbcChatMemoryRepository

Fixes #3442

Change timestamp generation to use second-level granularity instead of
milliseconds to ensure compatibility with MySQL/MariaDB default TIMESTAMP
precision (0 decimal places). The old code used millisecond timestamps that
were truncated to seconds on storage, causing messages saved within the same
second to have identical timestamps and random ordering.

The timestamp field functions as a sequence ID for message ordering rather
than a precise temporal record. Using second-level granularity with proper
incrementing ensures correct ordering across all database timestamp precisions
without requiring schema changes.

Also adds testMessageOrderWithLargeBatch() that saves 50 messages to validate
ordering is preserved. The original test with only 4 messages was passing by
chance despite the underlying bug.

Auto-cherry-pick to 1.0.x

Signed-off-by: Soby Chacko <soby.chacko@broadcom.com>

Author: sobychacko

memory/repository/spring-ai-model-chat-memory-repository-jdbc/src/main/java/org/springframework/ai/chat/memory/repository/jdbc/JdbcChatMemoryRepository.java

@@ -111,10 +111,13 @@ public static Builder builder() {
 	}
 
 	private record AddBatchPreparedStatement(String conversationId, List<Message> messages,
-			AtomicLong instantSeq) implements BatchPreparedStatementSetter {
+			AtomicLong sequenceId) implements BatchPreparedStatementSetter {
 
 		private AddBatchPreparedStatement(String conversationId, List<Message> messages) {
-			this(conversationId, messages, new AtomicLong(Instant.now().toEpochMilli()));
+			// Use second-level granularity to ensure compatibility with all database
+			// timestamp precisions. The timestamp serves as a sequence number for
+			// message ordering, not as a precise temporal record.
+			this(conversationId, messages, new AtomicLong(Instant.now().getEpochSecond()));
 		}
 
 		@Override
@@ -124,7 +127,9 @@ public void setValues(PreparedStatement ps, int i) throws SQLException {
 			ps.setString(1, this.conversationId);
 			ps.setString(2, message.getText());
 			ps.setString(3, message.getMessageType().name());
-			ps.setTimestamp(4, new Timestamp(this.instantSeq.getAndIncrement()));
+			// Convert seconds to milliseconds for Timestamp constructor.
+			// Each message gets a unique second value, ensuring proper ordering.
+			ps.setTimestamp(4, new Timestamp(this.sequenceId.getAndIncrement() * 1000L));
 		}
 
 		@Override

memory/repository/spring-ai-model-chat-memory-repository-jdbc/src/test/java/org/springframework/ai/chat/memory/repository/jdbc/AbstractJdbcChatMemoryRepositoryIT.java

@@ -185,6 +185,30 @@ void testMessageOrder() {
 				"4-Fourth message");
 	}
 
+	@Test
+	void testMessageOrderWithLargeBatch() {
+		var conversationId = UUID.randomUUID().toString();
+
+		// Create a large batch of 50 messages to ensure timestamp ordering issues
+		// are detected. With the old millisecond-precision code, MySQL/MariaDB's
+		// second-precision TIMESTAMP columns would truncate all timestamps to the
+		// same value, causing random ordering. This test validates the fix.
+		List<Message> messages = new java.util.ArrayList<>();
+		for (int i = 0; i < 50; i++) {
+			messages.add(new UserMessage("Message " + i));
+		}
+
+		this.chatMemoryRepository.saveAll(conversationId, messages);
+
+		List<Message> retrievedMessages = this.chatMemoryRepository.findByConversationId(conversationId);
+
+		// Verify we got all messages back in the exact order they were saved
+		assertThat(retrievedMessages).hasSize(50);
+		for (int i = 0; i < 50; i++) {
+			assertThat(retrievedMessages.get(i).getText()).isEqualTo("Message " + i);
+		}
+	}
+
 	/**
 	 * Base configuration for all integration tests.
 	 */