Overview ▹

Overview ▾

Package pgx is a PostgreSQL database driver.

pgx provides lower level access to PostgreSQL than the standard database/sql It remains as similar to the database/sql interface as possible while providing better speed and access to PostgreSQL specific features. Import github.com/jack/pgx/stdlib to use pgx as a database/sql compatible driver.

Query Interface

pgx implements Query and Scan in the familiar database/sql style.

var sum int32

// Send the query to the server. The returned rows MUST be closed
// before conn can be used again.
rows, err := conn.Query("select generate_series(1,$1)", 10)
if err != nil {
    return err
}

// rows.Close is called by rows.Next when all rows are read
// or an error occurs in Next or Scan. So it may optionally be
// omitted if nothing in the rows.Next loop can panic. It is
// safe to close rows multiple times.
defer rows.Close()

// Iterate through the result set
for rows.Next() {
    var n int32
    err = rows.Scan(&n)
    if err != nil {
        return err
    }
    sum += n
}

// Any errors encountered by rows.Next or rows.Scan will be returned here
if rows.Err() != nil {
    return err
}

// No errors found - do something with sum

pgx also implements QueryRow in the same style as database/sql.

var name string
var weight int64
err := conn.QueryRow("select name, weight from widgets where id=$1", 42).Scan(&name, &weight)
if err != nil {
    return err
}

Use Exec to execute a query that does not return a result set.

commandTag, err := conn.Exec("delete from widgets where id=$1", 42)
if err != nil {
    return err
}
if commandTag.RowsAffected() != 1 {
    return errors.New("No row found to delete")
}

Connection Pool

Connection pool usage is explicit and configurable. In pgx, a connection can be created and managed directly, or a connection pool with a configurable maximum connections can be used. Also, the connection pool offers an after connect hook that allows every connection to be automatically setup before being made available in the connection pool. This is especially useful to ensure all connections have the same prepared statements available or to change any other connection settings.

It delegates Query, QueryRow, Exec, and Begin functions to an automatically checked out and released connection so you can avoid manually acquiring and releasing connections when you do not need that level of control.

var name string
var weight int64
err := pool.QueryRow("select name, weight from widgets where id=$1", 42).Scan(&name, &weight)
if err != nil {
    return err
}

Base Type Mapping

pgx maps between all common base types directly between Go and PostgreSQL. In particular:

Go           PostgreSQL
-----------------------
string       varchar
             text

// Integers are automatically be converted to any other integer type if
// it can be done without overflow or underflow.
int8
int16        smallint
int32        int
int64        bigint
int
uint8
uint16
uint32
uint64
uint

// Floats are strict and do not automatically convert like integers.
float32      float4
float64      float8

time.Time   date
            timestamp
            timestamptz

[]byte      bytea

Null Mapping

pgx can map nulls in two ways. The first is Null* types that have a data field and a valid field. They work in a similar fashion to database/sql. The second is to use a pointer to a pointer.

var foo pgx.NullString
var bar *string
err := conn.QueryRow("select foo, bar from widgets where id=$1", 42).Scan(&a, &b)
if err != nil {
    return err
}

Array Mapping

pgx maps between int16, int32, int64, float32, float64, and string Go slices and the equivalent PostgreSQL array type. Go slices of native types do not support nulls, so if a PostgreSQL array that contains a null is read into a native Go slice an error will occur.

Hstore Mapping

pgx includes an Hstore type and a NullHstore type. Hstore is simply a map[string]string and is preferred when the hstore contains no nulls. NullHstore follows the Null* pattern and supports null values.

JSON and JSONB Mapping

pgx includes built-in support to marshal and unmarshal between Go types and the PostgreSQL JSON and JSONB.

Inet and Cidr Mapping

pgx encodes from net.IPNet to and from inet and cidr PostgreSQL types. In addition, as a convenience pgx will encode from a net.IP; it will assume a /32 netmask for IPv4 and a /128 for IPv6.

Custom Type Support

pgx includes support for the common data types like integers, floats, strings, dates, and times that have direct mappings between Go and SQL. Support can be added for additional types like point, hstore, numeric, etc. that do not have direct mappings in Go by the types implementing ScannerPgx and Encoder.

Custom types can support text or binary formats. Binary format can provide a large performance increase. The natural place for deciding the format for a value would be in ScannerPgx as it is responsible for decoding the returned data. However, that is impossible as the query has already been sent by the time the ScannerPgx is invoked. The solution to this is the global DefaultTypeFormats. If a custom type prefers binary format it should register it there.

pgx.DefaultTypeFormats["point"] = pgx.BinaryFormatCode

Note that the type is referred to by name, not by OID. This is because custom PostgreSQL types like hstore will have different OIDs on different servers. When pgx establishes a connection it queries the pg_type table for all types. It then matches the names in DefaultTypeFormats with the returned OIDs and stores it in Conn.PgTypes.

See example_custom_type_test.go for an example of a custom type for the PostgreSQL point type.

pgx also includes support for custom types implementing the database/sql.Scanner and database/sql/driver.Valuer interfaces.

Raw Bytes Mapping

[]byte passed as arguments to Query, QueryRow, and Exec are passed unmodified to PostgreSQL. In like manner, a *[]byte passed to Scan will be filled with the raw bytes returned by PostgreSQL. This can be especially useful for reading varchar, text, json, and jsonb values directly into a []byte and avoiding the type conversion from string.

Transactions

Transactions are started by calling Begin or BeginIso. The BeginIso variant creates a transaction with a specified isolation level.

tx, err := conn.Begin()
if err != nil {
    return err
}
// Rollback is safe to call even if the tx is already closed, so if
// the tx commits successfully, this is a no-op
defer tx.Rollback()

_, err = tx.Exec("insert into foo(id) values (1)")
if err != nil {
    return err
}

err = tx.Commit()
if err != nil {
    return err
}

Copy Protocol

Use CopyFrom to efficiently insert multiple rows at a time using the PostgreSQL copy protocol. CopyFrom accepts a CopyFromSource interface. If the data is already in a [][]interface{} use CopyFromRows to wrap it in a CopyFromSource interface. Or implement CopyFromSource to avoid buffering the entire data set in memory.

rows := [][]interface{}{
    {"John", "Smith", int32(36)},
    {"Jane", "Doe", int32(29)},
}

copyCount, err := conn.CopyFrom(
    "people",
    []string{"first_name", "last_name", "age"},
    pgx.CopyFromRows(rows),
)

CopyFrom can be faster than an insert with as few as 5 rows.

Listen and Notify

pgx can listen to the PostgreSQL notification system with the WaitForNotification function. It takes a maximum time to wait for a notification.

err := conn.Listen("channelname")
if err != nil {
    return nil
}

if notification, err := conn.WaitForNotification(time.Second); err != nil {
    // do something with notification
}

TLS

The pgx ConnConfig struct has a TLSConfig field. If this field is nil, then TLS will be disabled. If it is present, then it will be used to configure the TLS connection. This allows total configuration of the TLS connection.

Logging

pgx defines a simple logger interface. Connections optionally accept a logger that satisfies this interface. The log15 package (http://gopkg.in/inconshreveable/log15.v2) satisfies this interface and it is simple to define adapters for other loggers. Set LogLevel to control logging verbosity.

Name	Synopsis
..
examples
chat
todo
url_shortener
stdlib	Package stdlib is the compatibility layer from pgx to database/sql.

Package pgx

Overview ▹

Overview ▾

Query Interface

Connection Pool

Base Type Mapping

Null Mapping

Array Mapping

Hstore Mapping

JSON and JSONB Mapping

Inet and Cidr Mapping

Custom Type Support

Raw Bytes Mapping

Transactions

Copy Protocol

Listen and Notify

TLS

Logging

Index ▹

Index ▾

Package files

Internal call graph ▹

Internal call graph ▾

Constants

Variables

func Decode ¶

func Encode ¶

func FormatLSN ¶

func LogLevelFromString ¶

func ParseHstore ¶

func ParseLSN ¶

type AclItem ¶

type Char ¶

type Cid ¶

type CommandTag ¶

func (CommandTag) RowsAffected ¶

type Conn ¶

func Connect ¶

func (*Conn) Begin ¶

func (*Conn) BeginIso ¶

func (*Conn) CauseOfDeath ¶

func (*Conn) Close ¶

func (*Conn) CopyFrom ¶

func (*Conn) CopyTo ¶

func (*Conn) Deallocate ¶

func (*Conn) Exec ¶

func (*Conn) IsAlive ¶

func (*Conn) Listen ¶

func (*Conn) Prepare ¶

func (*Conn) PrepareEx ¶

func (*Conn) Query ¶

func (*Conn) QueryRow ¶

func (*Conn) SetLogLevel ¶

func (*Conn) SetLogger ¶

func (*Conn) Unlisten ¶

func (*Conn) WaitForNotification ¶

type ConnConfig ¶

func ParseConnectionString ¶

func ParseDSN ¶

func ParseEnvLibpq ¶

func ParseURI ¶

type ConnPool ¶

func NewConnPool ¶

func (*ConnPool) Acquire ¶

func (*ConnPool) Begin ¶

func (*ConnPool) BeginIso ¶

func (*ConnPool) Close ¶

func (*ConnPool) CopyFrom ¶

func (*ConnPool) CopyTo ¶

func (*ConnPool) Deallocate ¶

func (*ConnPool) Exec ¶

func (*ConnPool) Prepare ¶

func (*ConnPool) PrepareEx ¶

func (*ConnPool) Query ¶

func (*ConnPool) QueryRow ¶

func (*ConnPool) Release ¶

func (*ConnPool) Reset ¶

func (*ConnPool) Stat ¶

type ConnPoolConfig ¶

type ConnPoolStat ¶