如何限制使用FileIO写入的每个文件的行数 [英] How to limit number of lines per file written using FileIO

问题描述

是否可以使用TextIO限制每个书面分片中的行数，或者可以是FileIO?

Is there a possible way to limit number of lines in each written shard using TextIO or may be FileIO?

示例:

1. 从Big Query-Batch Job中读取行(例如，结果为19500行).
2. 进行一些转换.
3. 将文件写入Google Cloud存储(19个文件，每个文件限制为1000条记录，一个文件有500条记录).
4. 触发了Cloud Function，以针对GCS中的每个文件向外部API发出POST请求.

到目前为止，这是我要尝试执行的操作，但是不起作用(尝试限制每个文件1000行):

Here is what I'm trying to do so far but doesn't work (Trying to limit 1000 rows per file):

BQ_DATA = p | 'read_bq_view' >> beam.io.Read(
        beam.io.BigQuerySource(query=query,
                               use_standard_sql=True)) | beam.Map(json.dumps)

BQ_DATA | beam.WindowInto(GlobalWindows(), Repeatedly(trigger=AfterCount(1000)),
                              accumulation_mode=AccumulationMode.DISCARDING)
        | WriteToFiles(path='fileio', destination="csv")

我在概念上是错误的，还是有其他方法可以实现此目的?

Am I conceptually wrong or is there any other way to implement this?

推荐答案

您可以在ParDo中实现对GCS的写入步骤，并限制要包含在批处理"元素中的元素数量.像这样:

You can implement the write to GCS step inside ParDo and limit the number of elements to include in a "batch" like this:

from apache_beam.io import filesystems

class WriteToGcsWithRowLimit(beam.DoFn):
  def __init__(self, row_size=1000):
    self.row_size = row_size
    self.rows = []

  def finish_bundle(self):
     if len(self.rows) > 0:
        self._write_file()

  def process(self, element):
    self.rows.append(element)
    if len(self.rows) >= self.row_size:
        self._write_file()

  def _write_file(self):
    from time import time
    new_file = 'gs://bucket/file-{}.csv'.format(time())
    writer = filesystems.FileSystems.create(path=new_file)
    writer.write(self.rows) # may need to format
    self.rows = []
    writer.close()

BQ_DATA  | beam.ParDo(WriteToGcsWithRowLimit())

请注意，这不会创建少于1000行的任何文件，但是您可以更改process中的逻辑来做到这一点.

Note that this will not create any files with less than 1000 rows, but you can change the logic in process to do that.

(编辑1以处理余数)

(编辑2以停止使用计数器，因为文件将被覆盖)

(Edit 2 to stop using counters, as files will be overridden)

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