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Use database/sql style transaction interface

scan-io
Jack Christensen 2014-07-12 07:59:30 -05:00
parent f31665c5db
commit ae6a87545b
5 changed files with 60 additions and 316 deletions
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8
conn.go
View File

@ -23,14 +23,6 @@ import (
"time" "time"
) )
// Transaction isolation levels
const (
Serializable = "serializable"
RepeatableRead = "repeatable read"
ReadCommitted = "read committed"
ReadUncommitted = "read uncommitted"
)
// ConnConfig contains all the options used to establish a connection. // ConnConfig contains all the options used to establish a connection.
type ConnConfig struct { type ConnConfig struct {
Host string // host (e.g. localhost) or path to unix domain socket directory (e.g. /private/tmp) Host string // host (e.g. localhost) or path to unix domain socket directory (e.g. /private/tmp)

30
conn_pool.go
View File

@ -232,33 +232,3 @@ func (p *ConnPool) BeginIso(iso string) (*Tx, error) {
tx.pool = p tx.pool = p
return tx, nil return tx, nil
} }
// Transaction acquires a connection, delegates the call to that connection,
// and releases the connection. The call signature differs slightly from the
// underlying Transaction in that the callback function accepts a *Conn
func (p *ConnPool) Transaction(f func(conn *Conn) bool) (committed bool, err error) {
var c *Conn
if c, err = p.Acquire(); err != nil {
return
}
defer p.Release(c)
return c.Transaction(func() bool {
return f(c)
})
}
// TransactionIso acquires a connection, delegates the call to that connection,
// and releases the connection. The call signature differs slightly from the
// underlying TransactionIso in that the callback function accepts a *Conn
func (p *ConnPool) TransactionIso(isoLevel string, f func(conn *Conn) bool) (committed bool, err error) {
var c *Conn
if c, err = p.Acquire(); err != nil {
return
}
defer p.Release(c)
return c.TransactionIso(isoLevel, func() bool {
return f(c)
})
}

107
conn_pool_test.go
View File

@ -309,113 +309,62 @@ func TestConnPoolTransaction(t *testing.T) {
pool := createConnPool(t, 2) pool := createConnPool(t, 2)
defer pool.Close() defer pool.Close()
stats := pool.Stat()
if stats.CurrentConnections != 1 || stats.AvailableConnections != 1 {
t.Fatalf("Unexpected connection pool stats: %v", stats)
}
tx, err := pool.Begin() tx, err := pool.Begin()
if err != nil { if err != nil {
t.Fatalf("pool.Begin failed: %v", err) t.Fatalf("pool.Begin failed: %v", err)
} }
defer tx.Rollback()
var n int32 var n int32
err := pool.QueryRow("select 40+$1", 2).Scan(&n) err = tx.QueryRow("select 40+$1", 2).Scan(&n)
if err != nil { if err != nil {
t.Fatalf("pool.QueryRow Scan failed: %v", err) t.Fatalf("tx.QueryRow Scan failed: %v", err)
} }
if n != 42 { if n != 42 {
t.Errorf("Expected 42, got %d", n) t.Errorf("Expected 42, got %d", n)
} }
stats := pool.Stat() stats = pool.Stat()
if stats.CurrentConnections != 1 || stats.AvailableConnections != 0 {
t.Fatalf("Unexpected connection pool stats: %v", stats)
}
err = tx.Rollback()
if err != nil {
t.Fatalf("tx.Rollback failed: %v", err)
}
stats = pool.Stat()
if stats.CurrentConnections != 1 || stats.AvailableConnections != 1 { if stats.CurrentConnections != 1 || stats.AvailableConnections != 1 {
t.Fatalf("Unexpected connection pool stats: %v", stats) t.Fatalf("Unexpected connection pool stats: %v", stats)
} }
} }
func TestPoolTransaction(t *testing.T) { func TestConnPoolTransactionIso(t *testing.T) {
t.Parallel() t.Parallel()
pool := createConnPool(t, 2) pool := createConnPool(t, 2)
defer pool.Close() defer pool.Close()
committed, err := pool.Transaction(func(conn *pgx.Conn) bool { tx, err := pool.BeginIso(pgx.Serializable)
mustExec(t, conn, "create temporary table foo(id serial primary key)")
return true
})
if err != nil { if err != nil {
t.Fatalf("Transaction unexpectedly failed: %v", err) t.Fatalf("pool.Begin failed: %v", err)
}
if !committed {
t.Fatal("Transaction was not committed when it should have been")
} }
defer tx.Rollback()
committed, err = pool.Transaction(func(conn *pgx.Conn) bool { var level string
var n int64 err = tx.QueryRow("select current_setting('transaction_isolation')").Scan(&level)
err := conn.QueryRow("select count(*) from foo").Scan(&n)
if err != nil {
t.Fatalf("QueryRow.Scan failed: %v", err)
}
if n != 0 {
t.Fatalf("Did not receive expected value: %v", n)
}
mustExec(t, conn, "insert into foo(id) values(default)")
err = conn.QueryRow("select count(*) from foo").Scan(&n)
if err != nil {
t.Fatalf("QueryRow.Scan failed: %v", err)
}
if n != 1 {
t.Fatalf("Did not receive expected value: %v", n)
}
return false
})
if err != nil { if err != nil {
t.Fatalf("Transaction unexpectedly failed: %v", err) t.Fatalf("tx.QueryRow failed: %v", level)
}
if committed {
t.Fatal("Transaction was committed when it shouldn't have been")
} }
committed, err = pool.Transaction(func(conn *pgx.Conn) bool { if level != "serializable" {
var n int64 t.Errorf("Expected to be in isolation level %v but was %v", "serializable", level)
err := conn.QueryRow("select count(*) from foo").Scan(&n)
if err != nil {
t.Fatalf("QueryRow.Scan failed: %v", err)
}
if n != 0 {
t.Fatalf("Did not receive expected value: %v", n)
}
return true
})
if err != nil {
t.Fatalf("Transaction unexpectedly failed: %v", err)
}
if !committed {
t.Fatal("Transaction was not committed when it should have been")
}
}
func TestPoolTransactionIso(t *testing.T) {
t.Parallel()
pool := createConnPool(t, 2)
defer pool.Close()
committed, err := pool.TransactionIso("serializable", func(conn *pgx.Conn) bool {
var level string
conn.QueryRow("select current_setting('transaction_isolation')").Scan(&level)
if level != "serializable" {
t.Errorf("Expected to be in isolation level %v but was %v", "serializable", level)
}
return true
})
if err != nil {
t.Fatalf("Transaction unexpectedly failed: %v", err)
}
if !committed {
t.Fatal("Transaction was not committed when it should have been")
} }
} }

86
tx.go
View File

@ -5,10 +5,30 @@ import (
"fmt" "fmt"
) )
// Transaction isolation levels
const (
Serializable = "serializable"
RepeatableRead = "repeatable read"
ReadCommitted = "read committed"
ReadUncommitted = "read uncommitted"
)
var ErrTxClosed = errors.New("tx is closed")
// Begin starts a transaction with the default isolation level for the current
// connection. To use a specific isolation level see BeginIso.
func (c *Conn) Begin() (*Tx, error) { func (c *Conn) Begin() (*Tx, error) {
return c.begin("") return c.begin("")
} }
// BeginIso starts a transaction with isoLevel as the transaction isolation
// level.
//
// Valid isolation levels (and their constants) are:
// serializable (pgx.Serializable)
// repeatable read (pgx.RepeatableRead)
// read committed (pgx.ReadCommitted)
// read uncommitted (pgx.ReadUncommitted)
func (c *Conn) BeginIso(isoLevel string) (*Tx, error) { func (c *Conn) BeginIso(isoLevel string) (*Tx, error) {
return c.begin(isoLevel) return c.begin(isoLevel)
} }
@ -29,6 +49,10 @@ func (c *Conn) begin(isoLevel string) (*Tx, error) {
return &Tx{conn: c}, nil return &Tx{conn: c}, nil
} }
// Tx represents a database transaction.
//
// All Tx methods return ErrTxClosed if Commit or Rollback has already been
// called on the Tx.
type Tx struct { type Tx struct {
pool *ConnPool pool *ConnPool
conn *Conn conn *Conn
@ -38,7 +62,7 @@ type Tx struct {
// Commit commits the transaction // Commit commits the transaction
func (tx *Tx) Commit() error { func (tx *Tx) Commit() error {
if tx.closed { if tx.closed {
return errors.New("tx is closed") return ErrTxClosed
} }
_, err := tx.conn.Exec("commit") _, err := tx.conn.Exec("commit")
@ -46,10 +70,13 @@ func (tx *Tx) Commit() error {
return err return err
} }
// Rollback rolls back the transaction // Rollback rolls back the transaction. Rollback will return ErrTxClosed if the
// Tx is already closed, but is otherwise safe to call multiple times. Hence, a
// defer tx.Rollback() is safe even if tx.Commit() will be called first in a
// non-error condition.
func (tx *Tx) Rollback() error { func (tx *Tx) Rollback() error {
if tx.closed { if tx.closed {
return errors.New("tx is closed") return ErrTxClosed
} }
_, err := tx.conn.Exec("rollback") _, err := tx.conn.Exec("rollback")
@ -68,7 +95,7 @@ func (tx *Tx) close() {
// Exec delegates to the underlying *Conn // Exec delegates to the underlying *Conn
func (tx *Tx) Exec(sql string, arguments ...interface{}) (commandTag CommandTag, err error) { func (tx *Tx) Exec(sql string, arguments ...interface{}) (commandTag CommandTag, err error) {
if tx.closed { if tx.closed {
return CommandTag(""), errors.New("tx is closed") return CommandTag(""), ErrTxClosed
} }
return tx.conn.Exec(sql, arguments...) return tx.conn.Exec(sql, arguments...)
@ -78,7 +105,7 @@ func (tx *Tx) Exec(sql string, arguments ...interface{}) (commandTag CommandTag,
func (tx *Tx) Query(sql string, args ...interface{}) (*Rows, error) { func (tx *Tx) Query(sql string, args ...interface{}) (*Rows, error) {
if tx.closed { if tx.closed {
// Because checking for errors can be deferred to the *Rows, build one with the error // Because checking for errors can be deferred to the *Rows, build one with the error
err := errors.New("tx is closed") err := ErrTxClosed
return &Rows{closed: true, err: err}, err return &Rows{closed: true, err: err}, err
} }
@ -90,52 +117,3 @@ func (tx *Tx) QueryRow(sql string, args ...interface{}) *Row {
rows, _ := tx.conn.Query(sql, args...) rows, _ := tx.conn.Query(sql, args...)
return (*Row)(rows) return (*Row)(rows)
} }
// Transaction runs f in a transaction. f should return true if the transaction
// should be committed or false if it should be rolled back. Return value committed
// is if the transaction was committed or not. committed should be checked separately
// from err as an explicit rollback is not an error. Transaction will use the default
// isolation level for the current connection. To use a specific isolation level see
// TransactionIso
func (c *Conn) Transaction(f func() bool) (committed bool, err error) {
return c.transaction("", f)
}
// TransactionIso is the same as Transaction except it takes an isoLevel argument that
// it uses as the transaction isolation level.
//
// Valid isolation levels (and their constants) are:
// serializable (pgx.Serializable)
// repeatable read (pgx.RepeatableRead)
// read committed (pgx.ReadCommitted)
// read uncommitted (pgx.ReadUncommitted)
func (c *Conn) TransactionIso(isoLevel string, f func() bool) (committed bool, err error) {
return c.transaction(isoLevel, f)
}
func (c *Conn) transaction(isoLevel string, f func() bool) (committed bool, err error) {
var beginSql string
if isoLevel == "" {
beginSql = "begin"
} else {
beginSql = fmt.Sprintf("begin isolation level %s", isoLevel)
}
if _, err = c.Exec(beginSql); err != nil {
return
}
defer func() {
if committed && c.TxStatus == 'T' {
_, err = c.Exec("commit")
if err != nil {
committed = false
}
} else {
_, err = c.Exec("rollback")
committed = false
}
}()
committed = f()
return
}

145
tx_test.go
View File

@ -114,148 +114,3 @@ func TestBeginIso(t *testing.T) {
} }
} }
} }
func TestTransaction(t *testing.T) {
t.Parallel()
conn := mustConnect(t, *defaultConnConfig)
defer closeConn(t, conn)
createSql := `
create temporary table foo(
id integer,
unique (id) initially deferred
);
`
if _, err := conn.Exec(createSql); err != nil {
t.Fatalf("Failed to create table: %v", err)
}
// Transaction happy path -- it executes function and commits
committed, err := conn.Transaction(func() bool {
mustExec(t, conn, "insert into foo(id) values (1)")
return true
})
if err != nil {
t.Fatalf("Transaction unexpectedly failed: %v", err)
}
if !committed {
t.Fatal("Transaction was not committed")
}
var n int64
err = conn.QueryRow("select count(*) from foo").Scan(&n)
if err != nil {
t.Fatalf("QueryRow Scan failed: %v", err)
}
if n != 1 {
t.Fatalf("Did not receive correct number of rows: %v", n)
}
mustExec(t, conn, "truncate foo")
// It rolls back when passed function returns false
committed, err = conn.Transaction(func() bool {
mustExec(t, conn, "insert into foo(id) values (1)")
return false
})
if err != nil {
t.Fatalf("Transaction unexpectedly failed: %v", err)
}
if committed {
t.Fatal("Transaction should not have been committed")
}
err = conn.QueryRow("select count(*) from foo").Scan(&n)
if err != nil {
t.Fatalf("QueryRow Scan failed: %v", err)
}
if n != 0 {
t.Fatalf("Did not receive correct number of rows: %v", n)
}
// it rolls back changes when connection is in error state
committed, err = conn.Transaction(func() bool {
mustExec(t, conn, "insert into foo(id) values (1)")
if _, err := conn.Exec("invalid"); err == nil {
t.Fatal("Exec was supposed to error but didn't")
}
return true
})
if err != nil {
t.Fatalf("Transaction unexpectedly failed: %v", err)
}
if committed {
t.Fatal("Transaction was committed when it shouldn't have been")
}
err = conn.QueryRow("select count(*) from foo").Scan(&n)
if err != nil {
t.Fatalf("QueryRow Scan failed: %v", err)
}
if n != 0 {
t.Fatalf("Did not receive correct number of rows: %v", n)
}
// when commit fails
committed, err = conn.Transaction(func() bool {
mustExec(t, conn, "insert into foo(id) values (1)")
mustExec(t, conn, "insert into foo(id) values (1)")
return true
})
if err == nil {
t.Fatal("Transaction should have failed but didn't")
}
if committed {
t.Fatal("Transaction was committed when it should have failed")
}
err = conn.QueryRow("select count(*) from foo").Scan(&n)
if err != nil {
t.Fatalf("QueryRow Scan failed: %v", err)
}
if n != 0 {
t.Fatalf("Did not receive correct number of rows: %v", n)
}
// when something in transaction panics
func() {
defer func() {
recover()
}()
committed, err = conn.Transaction(func() bool {
mustExec(t, conn, "insert into foo(id) values (1)")
panic("stop!")
})
err = conn.QueryRow("select count(*) from foo").Scan(&n)
if err != nil {
t.Fatalf("QueryRow Scan failed: %v", err)
}
if n != 0 {
t.Fatalf("Did not receive correct number of rows: %v", n)
}
}()
}
func TestTransactionIso(t *testing.T) {
t.Parallel()
conn := mustConnect(t, *defaultConnConfig)
defer closeConn(t, conn)
isoLevels := []string{pgx.Serializable, pgx.RepeatableRead, pgx.ReadCommitted, pgx.ReadUncommitted}
for _, iso := range isoLevels {
_, err := conn.TransactionIso(iso, func() bool {
var level string
conn.QueryRow("select current_setting('transaction_isolation')").Scan(&level)
if level != iso {
t.Errorf("Expected to be in isolation level %v but was %v", iso, level)
}
return true
})
if err != nil {
t.Fatalf("Unexpected transaction failure: %v", err)
}
}
}