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sql.go
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sql.go
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// Package sql provides SQL implementations of the storage interface.
package sql
import (
"database/sql"
"regexp"
"github.com/cockroachdb/cockroach-go/crdb"
// import third party drivers
_ "github.com/go-sql-driver/mysql"
_ "github.com/lib/pq"
_ "github.com/mattn/go-sqlite3"
)
// flavor represents a specific SQL implementation, and is used to translate query strings
// between different drivers. Flavors shouldn't aim to translate all possible SQL statements,
// only the specific queries used by the SQL storages.
type flavor struct {
queryReplacers []replacer
// Optional function to create and finish a transaction. This is mainly for
// cockroachdb support which requires special retry logic provided by their
// client package.
//
// This will be nil for most flavors.
//
// See: https://github.com/cockroachdb/docs/blob/63761c2e/_includes/app/txn-sample.go#L41-L44
executeTx func(db *sql.DB, fn func(*sql.Tx) error) error
}
// A regexp with a replacement string.
type replacer struct {
re *regexp.Regexp
with string
}
// Match a postgres query binds. E.g. "$1", "$12", etc.
var bindRegexp = regexp.MustCompile(`\$\d+`)
func matchLiteral(s string) *regexp.Regexp {
return regexp.MustCompile(`\b` + regexp.QuoteMeta(s) + `\b`)
}
var (
// The "github.com/lib/pq" driver is the default flavor. All others are
// translations of this.
flavorPostgres = flavor{
// The default behavior for Postgres transactions is consistent reads, not consistent writes.
// For each transaction opened, ensure it has the correct isolation level.
//
// See: https://www.postgresql.org/docs/9.3/static/sql-set-transaction.html
//
// NOTE(ericchiang): For some reason using `SET SESSION CHARACTERISTICS AS TRANSACTION` at a
// session level didn't work for some edge cases. Might be something worth exploring.
executeTx: func(db *sql.DB, fn func(sqlTx *sql.Tx) error) error {
tx, err := db.Begin()
if err != nil {
return err
}
defer tx.Rollback()
if _, err := tx.Exec(`SET TRANSACTION ISOLATION LEVEL SERIALIZABLE;`); err != nil {
return err
}
if err := fn(tx); err != nil {
return err
}
return tx.Commit()
},
}
flavorSQLite3 = flavor{
queryReplacers: []replacer{
{bindRegexp, "?"},
// Translate for booleans to integers.
{matchLiteral("true"), "1"},
{matchLiteral("false"), "0"},
{matchLiteral("boolean"), "integer"},
// Translate other types.
{matchLiteral("bytea"), "blob"},
// {matchLiteral("timestamp"), "integer"},
// SQLite doesn't have a "now()" method, replace with "date('now')"
{regexp.MustCompile(`\bnow\(\)`), "date('now')"},
},
}
// Incomplete.
flavorMySQL = flavor{
queryReplacers: []replacer{
{bindRegexp, "?"},
},
}
// Not tested.
flavorCockroach = flavor{
executeTx: crdb.ExecuteTx,
}
)
func (f flavor) translate(query string) string {
// TODO(ericchiang): Heavy cashing.
for _, r := range f.queryReplacers {
query = r.re.ReplaceAllString(query, r.with)
}
return query
}
// conn is the main database connection.
type conn struct {
db *sql.DB
flavor flavor
}
func (c *conn) Close() error {
return c.db.Close()
}
// conn implements the same method signatures as encoding/sql.DB.
func (c *conn) Exec(query string, args ...interface{}) (sql.Result, error) {
query = c.flavor.translate(query)
return c.db.Exec(query, args...)
}
func (c *conn) Query(query string, args ...interface{}) (*sql.Rows, error) {
query = c.flavor.translate(query)
return c.db.Query(query, args...)
}
func (c *conn) QueryRow(query string, args ...interface{}) *sql.Row {
query = c.flavor.translate(query)
return c.db.QueryRow(query, args...)
}
// ExecTx runs a method which operates on a transaction.
func (c *conn) ExecTx(fn func(tx *trans) error) error {
if c.flavor.executeTx != nil {
return c.flavor.executeTx(c.db, func(sqlTx *sql.Tx) error {
return fn(&trans{sqlTx, c})
})
}
sqlTx, err := c.db.Begin()
if err != nil {
return err
}
if err := fn(&trans{sqlTx, c}); err != nil {
sqlTx.Rollback()
return err
}
return sqlTx.Commit()
}
type trans struct {
tx *sql.Tx
c *conn
}
// trans implements the same method signatures as encoding/sql.Tx.
func (t *trans) Exec(query string, args ...interface{}) (sql.Result, error) {
query = t.c.flavor.translate(query)
return t.tx.Exec(query, args...)
}
func (t *trans) Query(query string, args ...interface{}) (*sql.Rows, error) {
query = t.c.flavor.translate(query)
return t.tx.Query(query, args...)
}
func (t *trans) QueryRow(query string, args ...interface{}) *sql.Row {
query = t.c.flavor.translate(query)
return t.tx.QueryRow(query, args...)
}