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Combine project timestamps updates into a single statement

Krasimir Angelov requested to merge ka/combine-project-updates-on-event-creation into master

What does this MR do and why?

We currently have these Event callbacks:

  after_create :reset_project_activity
  after_create :set_last_repository_updated_at, if: :push_action?

Each one may produce separate UPDATE statements.

Old statements

-- reset_project_activity
UPDATE
        "projects"
SET
        "updated_at" = $ 1,
        "last_activity_at" = $ 2
WHERE
        "projects"."id" = $ 3
        AND (last_activity_at <= $ 4)
-- set_last_repository_updated_at
UPDATE
        "projects"
SET
        "updated_at" = $ 1,
        "last_repository_updated_at" = $ 2
WHERE
        "projects"."id" = $ 3
        AND (
                last_repository_updated_at < $ 4
                OR last_repository_updated_at IS NULL
        )

These two statements are one of the top contributors to WAL generated for projects table.

This MR combines them into a single statement, so that the write amplification cost is paid only once.

New combined statement

UPDATE
    "projects"
SET
    "updated_at" = '2024-06-25 22:16:40.944515',
        -- In case we are doing an update we can as well update both timestamps
    "last_activity_at" = '2024-06-25 22:16:40.944515',
    "last_repository_updated_at" = '2024-06-25 22:16:40.944515'
WHERE
    "projects"."id" = 333
        -- Execute the update only if one of these conditions is met
    AND (
        last_activity_at <= '2024-06-25 21:16:40.947778'
        OR last_repository_updated_at < '2024-06-25 22:11:40.948814'
        OR last_repository_updated_at IS NULL
    )

https://console.postgres.ai/gitlab/gitlab-production-main/sessions/29492/commands/91625

This query can change and include just one of the timestamps if the other was recently updated, for example

  • update only last_activity_at
  • update only last_repository_updated_at

This change is behind the combined_project_update_on_event_creation feature flag.

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Edited by Krasimir Angelov

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