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Ignore conflicting concurrent storage writes of the same data with version="*" #1118

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Ignore conflicting concurrent storage writes of the same data with version="*" #1118

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f26d9fc
Ignore insert if it exists.
ftkg Oct 25, 2023
a5cbeba
Update core_storage.go
ftkg Oct 25, 2023
b01f633
return success if writing same data
ftkg Oct 25, 2023
bde48e5
Change to a concurrent safe query.
ftkg Oct 26, 2023
1f13eed
Update core_storage.go
ftkg Oct 26, 2023
3decf87
Update core_storage.go
ftkg Oct 26, 2023
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8 changes: 6 additions & 2 deletions server/core_storage.go
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Original file line number Diff line number Diff line change
Expand Up @@ -698,11 +698,15 @@ func storagePrepBatch(batch *pgx.Batch, authoritativeWrite bool, op *StorageOpWr
// Existing permission checks are not applicable for new storage objects.
query = `
INSERT INTO storage (collection, key, user_id, value, version, read, write, create_time, update_time)
VALUES ($1, $2, $3, $4, $5, $6, $7, now(), now())
SELECT $1, $2, $3, $4, $5, $6, $7, now(), now()
WHERE NOT EXISTS(SELECT 1 FROM storage WHERE collection = $1 AND key = $2 AND user_id = $3) -- avoids ON CONFLICT hitting pre-existing object, and immediately cancels insert
ON CONFLICT (collection, key, user_id) DO UPDATE
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SET version = excluded.version WHERE storage.version = excluded.version AND storage.read = excluded.read AND storage.write = excluded.write -- needed to return a row on concurrent write of same object
RETURNING read, write, version, create_time, update_time`

// Outcomes:
// - NoRows - insert failed due to constraint violation (concurrent insert)
// - Row is returned if object was new or if concurrent writer wrote object with the same values (ON CONFLICT UPDATE needed)
// - NoRows - insert was ignored due to constraint violation (non-OCC already existing row), or concurrent write wrote object with different values (UPDATE did not happen)
}

batch.Queue(query, params...)
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