Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Jump to bottom

Add support for AVG on sharded queries #14419

Merged
merged 6 commits into from
Nov 8, 2023
Merged

Add support for AVG on sharded queries #14419

merged 6 commits into from
Nov 8, 2023

Conversation

systay
Copy link
Collaborator

@systay systay commented Nov 1, 2023 •
edited
Loading

Description

Adds support for AVG on queries that need to be sharded. We can't just send down AVG to each shard and average these together. We need to turn AVG into SUM/COUNT, which is easy to shard.

Paired with @arthurschreiber on this

Related Issue(s)

Fixes #9397

Checklist

  • "Backport to:" labels have been added if this change should be back-ported
  • Tests were added or are not required
  • Did the new or modified tests pass consistently locally and on the CI
  • Documentation was added or is not required

@vitess-bot vitess-bot
Copy link
Contributor

vitess-bot bot commented Nov 1, 2023

Review Checklist

Hello reviewers! 👋 Please follow this checklist when reviewing this Pull Request.

General

  • Ensure that the Pull Request has a descriptive title.
  • Ensure there is a link to an issue (except for internal cleanup and flaky test fixes), new features should have an RFC that documents use cases and test cases.

Tests

  • Bug fixes should have at least one unit or end-to-end test, enhancement and new features should have a sufficient number of tests.

Documentation

  • Apply the release notes (needs details) label if users need to know about this change.
  • New features should be documented.
  • There should be some code comments as to why things are implemented the way they are.
  • There should be a comment at the top of each new or modified test to explain what the test does.

New flags

  • Is this flag really necessary?
  • Flag names must be clear and intuitive, use dashes (-), and have a clear help text.

If a workflow is added or modified:

  • Each item in Jobs should be named in order to mark it as required.
  • If the workflow needs to be marked as required, the maintainer team must be notified.

Backward compatibility

  • Protobuf changes should be wire-compatible.
  • Changes to _vt tables and RPCs need to be backward compatible.
  • RPC changes should be compatible with vitess-operator
  • If a flag is removed, then it should also be removed from vitess-operator and arewefastyet, if used there.
  • vtctl command output order should be stable and awk-able.

@vitess-bot vitess-bot bot added NeedsDescriptionUpdate The description is not clear or comprehensive enough, and needs work NeedsIssue A linked issue is missing for this Pull Request NeedsWebsiteDocsUpdate What it says labels Nov 1, 2023
@github-actions github-actions bot added this to the v19.0.0 milestone Nov 1, 2023
@systay systay added Type: Enhancement Logical improvement (somewhere between a bug and feature) Component: Query Serving and removed NeedsDescriptionUpdate The description is not clear or comprehensive enough, and needs work NeedsWebsiteDocsUpdate What it says NeedsIssue A linked issue is missing for this Pull Request labels Nov 7, 2023
@systay systay marked this pull request as ready for review November 7, 2023 08:13
arthurschreiber
arthurschreiber approved these changes Nov 7, 2023
View reviewed changes
go/vt/vtgate/planbuilder/operators/aggregation_pushing.go
}

if avg.Distinct {
panic(vterrors.VT12001("AVG(distinct <>)"))
Copy link
Contributor

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Just for my understanding, supporting this would require loading all the distinct values from the shard, and then perform the avg calculation on the vtgate layer.

Copy link
Collaborator Author

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

I'm not sure. Have not spent enough time thinking about it to come up with a solution, which is why I just fail here.

go/vt/vtgate/planbuilder/operators/aggregation_pushing.go
Comment on lines +849 to +853
calcExpr := &sqlparser.BinaryExpr{
Operator: sqlparser.DivOp,
Left: sumExpr,
Right: countExpr,
}
Copy link
Contributor

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

❤️

go/vt/vtgate/planbuilder/operators/aggregation_pushing.go Show resolved Hide resolved
systay
systay commented Nov 7, 2023
View reviewed changes
go/vt/vtgate/planbuilder/testdata/aggr_cases.json
"QueryType": "SELECT",
"Original": "select avg(id)+count(foo)+bar from user group by bar",
"Instructions": {
"OperatorType": "Projection",
Copy link
Collaborator Author

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

We should add logic to compact two projections into a single one. Not part of this PR, just commenting for future reference

Copy link
Member

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

better to create an issue for it.

systay
systay commented Nov 7, 2023
View reviewed changes
go/vt/vtgate/planbuilder/testdata/aggr_cases.json
{
"OperatorType": "Aggregate",
"Variant": "Scalar",
"Aggregates": "sum(0) AS avg(foo), sum_count(1) AS count(foo), sum_count(2) AS count(foo)",
Copy link
Collaborator Author

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

no need to have count twice here. could/should optimise this

vmg
vmg approved these changes Nov 8, 2023
View reviewed changes
Copy link
Collaborator

@vmg vmg left a comment

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Looks pretty :gucci: my friend 👌

GuptaManan100
GuptaManan100 approved these changes Nov 8, 2023
View reviewed changes
Copy link
Member

@GuptaManan100 GuptaManan100 left a comment

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

LGTM!

go/vt/vtgate/planbuilder/testdata/aggr_cases.json
{
"OperatorType": "Aggregate",
"Variant": "Scalar",
"Aggregates": "sum(0) AS avg(foo), sum_count(1) AS count(foo), sum_count(2) AS count(foo)",
Copy link
Member

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Shouldn't that be sum(0) as sum(foo)? Maybe its just a display thing

Copy link
Collaborator Author

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

yeah, it's just a display thing. that alias is only seen in the plans

@harshit-gangal
Copy link
Member

Nice to add avg to fuzzer now.

@systay systay merged commit 225fc70 into vitessio:main Nov 8, 2023
115 checks passed
@systay systay deleted the avg branch November 8, 2023 10:28
ejortegau pushed a commit to slackhq/vitess that referenced this pull request Dec 13, 2023
@systay @ejortegau
Add support for AVG on sharded queries (vitessio#14419)
cb30f78
@harshit-gangal harshit-gangal mentioned this pull request Mar 27, 2024
Closed
@GuptaManan100 GuptaManan100 mentioned this pull request Jul 26, 2024
Closed
Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment
Reviewers

@arthurschreiber arthurschreiber arthurschreiber approved these changes

@GuptaManan100 GuptaManan100 GuptaManan100 approved these changes

@harshit-gangal harshit-gangal harshit-gangal approved these changes

@vmg vmg vmg approved these changes

@frouioui frouioui Awaiting requested review from frouioui frouioui is a code owner

Assignees
No one assigned
Labels
Component: Query Serving Type: Enhancement Logical improvement (somewhere between a bug and feature)
Projects
None yet
Milestone
v19.0.0
Development

Successfully merging this pull request may close these issues.

support cross-shard avg
5 participants
@systay @harshit-gangal @arthurschreiber @vmg @GuptaManan100