Response too large to return with LIMIT 1;

问题

I was playing with bigquery and ran into a problem, my Query was:

SELECT * FROM (
SELECT a.title,  a.counter , MAX(b.num_characters) as max
FROM (
  SELECT title, count(*) as counter FROM publicdata:samples.wikipedia
  GROUP EACH BY title
  ORDER BY counter DESC
  LIMIT 10
) a JOIN
(SELECT title,num_characters FROM publicdata:samples.wikipedia
) b ON a.title = b.title
GROUP BY a.title, a.counter)
LIMIT 1;

Although this is valid, I'm getting response too large to return. The first Subquery is running fine, what I want to do is get a bit more column for it. But I fail.

回答1:

Don't worry about the "limit 1", the response gets too large before reaching that stage.

Try skipping the second subquery, as it is only selecting 2 columns from the large dataset, without filtering it. A working alternative is:

SELECT
  a.title, a.counter, MAX(b.num_characters) AS max
FROM
  publicdata:samples.wikipedia b JOIN(
  SELECT
    title, COUNT(*) AS counter
  FROM
    publicdata:samples.wikipedia
    GROUP EACH BY title
  ORDER BY
    counter DESC
  LIMIT 10) a
  ON a.title = b.title
GROUP BY
  a.title,
  a.counter

This runs in 15.4 seconds.

We can do it faster, using TOP():

SELECT
  a.title title, counter, MAX(num_characters) max
FROM
  publicdata:samples.wikipedia b
JOIN
  (
  SELECT
    TOP(title, 10) AS title, COUNT(*) AS counter
  FROM
    publicdata:samples.wikipedia
    ) a
  ON a.title=b.title
GROUP BY
  title, counter

TOP() acts as a simpler and faster (SELECT COUNT(*)/GROUP/LIMIT).

https://developers.google.com/bigquery/docs/query-reference#top-function

Now it runs in only 6.5s, processing 15.9 GB.

来源：https://stackoverflow.com/questions/16335574/response-too-large-to-return-with-limit-1

标签

google-bigquery