gosora/common/meta/meta_store.go

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package common
import (
"database/sql"
qgen "github.com/Azareal/Gosora/query_gen"
)
// MetaStore is a simple key-value store for the system to stash things in when needed
type MetaStore interface {
Get(name string) (val string, err error)
Set(name, val string) error
}
type DefaultMetaStore struct {
get *sql.Stmt
set *sql.Stmt
add *sql.Stmt
}
func NewDefaultMetaStore(acc *qgen.Accumulator) (*DefaultMetaStore, error) {
m := &DefaultMetaStore{
get: acc.Select("meta").Columns("value").Where("name = ?").Prepare(),
set: acc.Update("meta").Set("value = ?").Where("name = ?").Prepare(),
add: acc.Insert("meta").Columns("name,value").Fields("?,''").Prepare(),
}
return m, acc.FirstError()
}
func (s *DefaultMetaStore) Get(name string) (val string, err error) {
err = s.get.QueryRow(name).Scan(&val)
return val, err
}
// TODO: Use timestamped rows as a more robust method of ensuring data integrity
func (s *DefaultMetaStore) Set(name, val string) error {
_, err := s.Get(name)
if err == sql.ErrNoRows {
_, err := s.add.Exec(name)
if err != nil {
return err
}
}
_, err = s.set.Exec(val, name)
return err
}