如何使用python Dedupe有效地将记录链接到大表？

Question

我正在尝试使用该Dedupe包将一个小杂乱的数据合并到一个规范表.由于规范表非常大(1.22亿行),我无法将其全部加载到内存中.

目前的做法,我使用基于关闭这个发生在测试数据一整天:存储在一个字典凌乱数据的300K行的表,并将其存储在MySQL的规范数据的60万行的表.如果我在内存中完成所有操作(作为dict读取规范表),它只需要半个小时.

有没有办法让这个更有效率？

blocked_pairs = block_data(messy_data, canonical_db_cursor, gazetteer)
clustered_dupes = gazetteer.matchBlocks(blocked_pairs, 0)

def block_data(messy_data, c, gazetteer):

    block_groups = itertools.groupby(gazetteer.blocker(messy_data.viewitems()),
                                     lambda x: x[1])
    for (record_id, block_keys) in block_groups:

        a = [(record_id, messy_data[record_id], set())]

        c.execute("""SELECT *
                    FROM canonical_table
                    WHERE record_id IN
                        (SELECT DISTINCT record_id
                         FROM blocking_map
                         WHERE block_key IN %s)""", 
                  (tuple(block_key for block_key, _ in block_keys),))

        b = [(row[self.key], row, set()) for row in c]

        if b:
            yield (a, b)

Answer 1

通过将查询分成两个查询，可以显着加快速度。我正在使用mysql并且示例中使用的所有列都已索引...

def block_data(messy_data, c, gazetteer):

    block_groups = itertools.groupby(gazetteer.blocker(messy_data.viewitems()),
                                 lambda x: x[1])
    for (record_id, block_keys) in block_groups:

        a = [(record_id, messy_data[record_id], set())]

        c.execute("""SELECT DISTINCT record_id
                     FROM blocking_map
                     WHERE block_key IN %s""", 
                  (tuple(block_key for block_key, _ in block_keys),))

        values = tuple(row['record_id'] for row in c)

        if values:

            c.execute("""SELECT *
                         FROM canonical_table
                         WHERE record_id IN %s""",
                      (values,))

            b = [(row['record_id'], row, set())
                 for row in c]

            if b:
                yield (a, b)