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clair/database/pgsql/keyvalue.go

86 lines
2.6 KiB

// Copyright 2017 clair authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package pgsql
import (
"database/sql"
"time"
log "github.com/sirupsen/logrus"
"github.com/coreos/clair/pkg/commonerr"
)
// InsertKeyValue stores (or updates) a single key / value tuple.
func (pgSQL *pgSQL) InsertKeyValue(key, value string) (err error) {
if key == "" || value == "" {
log.Warning("could not insert a flag which has an empty name or value")
return commonerr.NewBadRequestError("could not insert a flag which has an empty name or value")
}
defer observeQueryTime("InsertKeyValue", "all", time.Now())
// Upsert.
//
// Note: UPSERT works only on >= PostgreSQL 9.5 which is not yet supported by AWS RDS.
// The best solution is currently the use of http://dba.stackexchange.com/a/13477
// but the key/value storage doesn't need to be super-efficient and super-safe at the
// moment so we can just use a client-side solution with transactions, based on
// http://postgresql.org/docs/current/static/plpgsql-control-structures.html.
// TODO(Quentin-M): Enable Upsert as soon as 9.5 is stable.
for {
// First, try to update.
r, err := pgSQL.Exec(updateKeyValue, value, key)
if err != nil {
return handleError("updateKeyValue", err)
}
if n, _ := r.RowsAffected(); n > 0 {
// Updated successfully.
return nil
}
// Try to insert the key.
// If someone else inserts the same key concurrently, we could get a unique-key violation error.
_, err = pgSQL.Exec(insertKeyValue, key, value)
if err != nil {
if isErrUniqueViolation(err) {
// Got unique constraint violation, retry.
continue
}
return handleError("insertKeyValue", err)
}
return nil
}
}
// GetValue reads a single key / value tuple and returns an empty string if the key doesn't exist.
func (pgSQL *pgSQL) GetKeyValue(key string) (string, error) {
defer observeQueryTime("GetKeyValue", "all", time.Now())
var value string
err := pgSQL.QueryRow(searchKeyValue, key).Scan(&value)
if err == sql.ErrNoRows {
return "", nil
}
if err != nil {
return "", handleError("searchKeyValue", err)
}
return value, nil
}