pgsql/migrations: add index on Vulnerability_Notification.deleted_at #280
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Quentin-M
added
area/performance
`searchNotificationAvailable` never effectively use any indexes because: - `notified_at < $1`, where $1 is a recent timestamp, returns the majority of the table and therefore it is cheaper for PostgreSQL to use a sequential scan on the table. - there is no index for `deleted_at IS NULL`. However, when Clair has been running for long enough, the grand majority of rows (99%+) are expected to have a non-NULL `deleted_at` field. This commit adds a new index on this very field in order to fetch the remaining 1% in the blink of an eye. In other words, instead of realizing a full table scan for each `searchNotificationAvailable` query, we'll use the small branch of a new index, reducing the total cost from over 30k to a mere 150 on a Clair database that has already managed more than 1 000 000 notifications.
Quentin-M
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jzelinskie
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Dec 6, 2016
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searchNotificationAvailablenever effectively use any indexes because:notified_at < $1, where $1 is a recent timestamp, returns themajority of the table and therefore it is cheaper for PostgreSQL
to use a sequential scan on the table.
deleted_at IS NULL.However, when Clair has been running for long enough, the grand majority
of rows (99%+) are expected to have a non-NULL
deleted_atfield. Thiscommit adds a new index on this very field in order to fetch the
remaining 1% in the blink of an eye.
In other words, instead of realizing a full table scan for each
searchNotificationAvailablequery, we'll use the small branch of a newindex, reducing the total cost from over 30k to a mere 150 on a Clair
database that has already managed more than 1 000 000 notifications.