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Merge pull request #281 from coreos/dis_hashjoins_introducing

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pgsql: Disable hashjoins to get introducing layers for notifications
This commit is contained in:
Quentin Machu 2016-12-06 19:48:33 +01:00 committed by GitHub
commit 83b5538c65
1 changed files with 22 additions and 1 deletions
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23
database/pgsql/notification.go
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@ -159,11 +159,32 @@ func (pgSQL *pgSQL) loadLayerIntroducingVulnerability(vulnerability *database.Vu
return -1, nil
}
// Create a transaction to disable hash joins as our experience shows that
// PostgreSQL plans in certain cases a sequential scan and a hash on
// Layer_diff_FeatureVersion for the condition `ldfv.layer_id >= $2 AND
// ldfv.modification = 'add'` before realizing a hash inner join with
// Vulnerability_Affects_FeatureVersion. By disabling explictly hash joins,
// we force PostgreSQL to perform a bitmap index scan with
// `ldfv.featureversion_id = fv.id` on Layer_diff_FeatureVersion, followed by
// a bitmap heap scan on `ldfv.layer_id >= $2 AND ldfv.modification = 'add'`,
// thus avoiding a sequential scan on the biggest database table and
// allowing a small nested loop join instead.
tx, err := pgSQL.Begin()
if err != nil {
return -1, handleError("searchNotificationLayerIntroducingVulnerability.Begin()", err)
}
defer tx.Commit()
_, err = tx.Exec(disableHashJoin)
if err != nil {
log.Warningf("searchNotificationLayerIntroducingVulnerability: could not disable hash join: %s", err)
}
// We do `defer observeQueryTime` here because we don't want to observe invalid calls.
defer observeQueryTime("loadLayerIntroducingVulnerability", "all", tf)
// Query with limit + 1, the last item will be used to know the next starting ID.
rows, err := pgSQL.Query(searchNotificationLayerIntroducingVulnerability,
rows, err := tx.Query(searchNotificationLayerIntroducingVulnerability,
vulnerability.ID, startID, limit+1)
if err != nil {
return 0, handleError("searchNotificationLayerIntroducingVulnerability", err)