paimon-python/pypaimon/read/reader/deduplicate_merge_function.py

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"""Default merge function for primary-key tables.

Mirrors Java ``DeduplicateMergeFunction`` -- for a run of KVs sharing
the same primary key, keep only the one with the highest sequence
number (by virtue of ``add`` being called in sequence-number order).
"""

from typing import Optional

from pypaimon.table.row.key_value import KeyValue


class DeduplicateMergeFunction:
    """Keep only the latest KV per primary key.

    Used by both the read path (``SortMergeReaderWithMinHeap``) and the
    write path (``KeyValueDataWriter`` in-memory merge buffer) -- the
    latter is what enforces the LSM "PK unique within a file"
    invariant on flush.
    """

    def __init__(self):
        self.latest_kv: Optional[KeyValue] = None

    def reset(self) -> None:
        self.latest_kv = None

    def add(self, kv: KeyValue) -> None:
        self.latest_kv = kv

    def get_result(self) -> Optional[KeyValue]:
        return self.latest_kv