feat: optimize the indexes for session/continuity cleanup, SPLAT-930

[abador]

Related issue(s)

Checklist

• I have read the contributing guidelines.
• I have referenced an issue containing the design document if my change
  introduces a new feature.
• I am following the
  contributing code guidelines.
• I have read the security policy.
• I confirm that this pull request does not address a security
  vulnerability. If this pull request addresses a security vulnerability, I
  confirm that I got the approval (please contact
  security@ory.sh) from the maintainers to push
  the changes.
• I have added tests that prove my fix is effective or that my feature
  works.
• I have added or changed the documentation.

Further Comments

[mmeller-wikia]

Question: Do we need this index?

[mmeller-wikia]

Question: Do we need this index?

[mmeller-wikia]

Suggestion: I am not sure if these changes will actually speed up cleanup process, as we are removing up to 5000 rows from each table each 5min.
Could we purge all stale rows instead in one run?
If yes, we might run it once per hour and reclaim some k8s resources

kratos/persistence/sql/persister.go

Lines 189 to 250 in 85e88d0

	func (p *Persister) CleanupDatabase(ctx context.Context, wait time.Duration, older time.Duration, batchSize int) error {
	currentTime := time.Now().Add(-older)
	p.r.Logger().Printf("Cleaning up records older than %s\n", currentTime)
	p.r.Logger().Println("Cleaning up expired sessions")
	if err := p.DeleteExpiredSessions(ctx, currentTime, batchSize); err != nil {
	return err
	}
	time.Sleep(wait)
	p.r.Logger().Println("Cleaning up expired continuity containers")
	if err := p.DeleteExpiredContinuitySessions(ctx, currentTime, batchSize); err != nil {
	return err
	}
	time.Sleep(wait)
	p.r.Logger().Println("Cleaning up expired login flows")
	if err := p.DeleteExpiredLoginFlows(ctx, currentTime, batchSize); err != nil {
	return err
	}
	time.Sleep(wait)
	p.r.Logger().Println("Cleaning up expired recovery flows")
	if err := p.DeleteExpiredRecoveryFlows(ctx, currentTime, batchSize); err != nil {
	return err
	}
	time.Sleep(wait)
	p.r.Logger().Println("Cleaning up expired registation flows")
	if err := p.DeleteExpiredRegistrationFlows(ctx, currentTime, batchSize); err != nil {
	return err
	}
	time.Sleep(wait)
	p.r.Logger().Println("Cleaning up expired settings flows")
	if err := p.DeleteExpiredSettingsFlows(ctx, currentTime, batchSize); err != nil {
	return err
	}
	time.Sleep(wait)
	p.r.Logger().Println("Cleaning up expired verification flows")
	if err := p.DeleteExpiredVerificationFlows(ctx, currentTime, batchSize); err != nil {
	return err
	}
	time.Sleep(wait)
	p.r.Logger().Println("Cleaning up expired session token exchangers")
	if err := p.DeleteExpiredExchangers(ctx, currentTime, batchSize); err != nil {
	return err
	}
	time.Sleep(wait)
	p.r.Logger().Println("Cleaning seen selfservice errors")
	if err := p.ClearErrorContainers(ctx, older, false); err != nil {
	return err
	}
	time.Sleep(wait)
	p.r.Logger().Println("Successfully cleaned up the latest batch of the SQL database! " +
	"This should be re-run periodically, to be sure that all expired data is purged.")
	return nil
	}