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From "ASF GitHub Bot (Jira)" <>
Subject [jira] [Commented] (AIRFLOW-5930) Reduce time spent building SQL strings
Date Wed, 11 Dec 2019 20:08:00 GMT


ASF GitHub Bot commented on AIRFLOW-5930:

ashb commented on pull request #6792: [AIRFLOW-5930] Use cached-SQL query building for hot-path
   Make sure you have checked _all_ steps below.
   ### Jira
   - [x]
   ### Description
   - [ ] Building the SQL string for this query takes up about 25% of the time that the DAG
parsing process spends, so replacing this one query should help speed up the rate at which
the scheduler can queue tasks.
     See for more info. The docs
explain a lot of how/why this works, so rather than rebuilding them from string 10s of times
(once per task per active dag run) we cache the build SQL string!
     I will collect up-to-date performance numbers against master, but this makes the "dag
parsing" process of the scheduler (which creates and updates dag runs, and creates Task Instances)
about 2x quicker:
     Concurrent DagRuns | Tasks | Before | After | Speedup
     -- | -- | -- | -- | --
     2 | 12 | 0.146s (±0.0163s) | 0.074s (±0.0037s) | x1.97
     10 | 12 | 1.11s (±0.0171s) | 0.266s (±0.0229s) | x4.17
     40 | 12 | 4.28s (±0.101s) | 0.852s (±0.0113s) | x5.02
     40 | 40 | 6.72s (±0.067s) | 2.659s (±0.0283s) | x2.53
   ### Tests
   - [x] No new tests, no change in behaviour.
   ### Commits
   - [ ] My commits all reference Jira issues in their subject lines, and I have squashed
multiple commits if they address the same issue. In addition, my commits follow the guidelines
from "[How to write a good git commit message](":
     1. Subject is separated from body by a blank line
     1. Subject is limited to 50 characters (not including Jira issue reference)
     1. Subject does not end with a period
     1. Subject uses the imperative mood ("add", not "adding")
     1. Body wraps at 72 characters
     1. Body explains "what" and "why", not "how"
   ### Documentation
   - [ ] In case of new functionality, my PR adds documentation that describes how to use
     - All the public functions and the classes in the PR contain docstrings that explain
what it does
     - If you implement backwards incompatible changes, please leave a note in the [](
so we can assign it to a appropriate release
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> Reduce time spent building SQL strings
> --------------------------------------
>                 Key: AIRFLOW-5930
>                 URL:
>             Project: Apache Airflow
>          Issue Type: Improvement
>          Components: scheduler
>    Affects Versions: 2.0.0
>            Reporter: Ash Berlin-Taylor
>            Assignee: Ash Berlin-Taylor
>            Priority: Major
> My profling of the scheduler work turned up a lot of cases where the scheduler_job/dag
parser process was spending a lot of time building (not executing!) the SQL string.
> This can be improved with

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