[GitHub] [incubator-superset] mistercrunch commented on issue #7204: how to improvee the rendering speed

[GitBox <gi...@apache.org>]

mistercrunch commented on issue #7204: how to improvee the rendering speed
URL: https://github.com/apache/incubator-superset/issues/7204#issuecomment-479351139
 
 
   A few things here, first is that the term `rendering` is misleading. Assuming your database is in async mode, here's some of what's happening. You can track some of this using `statsd` logging if it's configured
   * query executes:`sqllab.query.time_executing_query`
   * fetching data: `sqllab.query.time_fetching_results`
   * state is changed to `rendering`
   * data is pushed to results backend: `sqllab.query.results_backend_write`
   * client is polling
   * data is available, request is sent to get the full result set
   * fetching over network
   * actual rendering on the browser starts
   
   If you can just limit your query, all of this will be much faster.
   
   The reason why the postgres client is fast, is that it doesn't fetch all the data upfront, at step 2 (fetching data), it fetches a page and shows it. The cursor is kept alive and can be used to retrieve more rows as you scroll.
   
   We could improve all this to be more seamless/faster, but operating in async mode makes all of this more complicated. I think we'll improve this over time. One approach would be to deliver the data in two phases, with a new state `partially-delivered` or something like that.

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