Fix #46

Issue Description

The issue occurs when incremental mode insert is used, and sling tries to directly compare UTC (CSV) with UTC+8 (Proton). The comparison is performed using to_time, which is not smart enough to detect the timezone properly.

Reproduction Steps

1. Create 2 streams in Proton

CREATE STREAM src
             (
               `id` int64,
               `_tp_time` datetime64(3, 'Asia/Shanghai') DEFAULT now64(3, 'Asia/Shanghai') CODEC(DoubleDelta, LZ4)
             );

CREATE STREAM tgt
             (
               `id` int64,
               `_tp_time` datetime64(3, 'Asia/Shanghai') DEFAULT now64(3, 'Asia/Shanghai') CODEC(DoubleDelta, LZ4)
             );

2. Insert an older record

INSERT INTO src(id, _tp_time) VALUES(1, '2025-07-18 22:00:00');

3. Run Proton → CSV → Proton transfer

./sling run --src-conn LOCAL --src-stream "src" --tgt-conn FILE --tgt-object "old.csv" --mode incremental --update-key _tp_time -d

./sling run --src-conn FILE --src-stream "old.csv" --tgt-conn LOCAL --tgt-object "tgt" --mode incremental --update-key _tp_time -d

4. Insert a new record (gap between newer and older records is less than 8 hours)

INSERT INTO src(id, _tp_time) VALUES(2, '2025-07-19 05:00:00');

5. Run Proton → CSV → Proton transfer again

./sling run --src-conn LOCAL --src-stream "src" --tgt-conn FILE --tgt-object "new.csv" --mode incremental --update-key _tp_time -d

./sling run --src-conn FILE --src-stream "new.csv" --tgt-conn LOCAL --tgt-object "tgt" --mode incremental --update-key _tp_time -d

6. Verify the final count

SELECT * FROM table(tgt);

Expected vs Actual Results

• Expected: 2 rows returned
• Actual (old sling): Only 1 row returned