Involved Source Filesauth_scram.goconfig.godefaults.go
Package pgconn is a low-level PostgreSQL database driver.
pgconn provides lower level access to a PostgreSQL connection than a database/sql or pgx connection. It operates at
nearly the same level is the C library libpq.
Establishing a Connection
Use Connect to establish a connection. It accepts a connection string in URL or DSN and will read the environment for
libpq style environment variables.
Executing a Query
ExecParams and ExecPrepared execute a single query. They return readers that iterate over each row. The Read method
reads all rows into memory.
Executing Multiple Queries in a Single Round Trip
Exec and ExecBatch can execute multiple queries in a single round trip. They return readers that iterate over each query
result. The ReadAll method reads all query results into memory.
Context Support
All potentially blocking operations take a context.Context. If a context is canceled while the method is in progress the
method immediately returns. In most circumstances, this will close the underlying connection.
The CancelRequest method may be used to request the PostgreSQL server cancel an in-progress query without forcing the
client to abort.
errors.gopgconn.go
Package-Level Type Names (total 28, in which 21 are exported)
Batch is a collection of queries that can be sent to the PostgreSQL server in a single round-trip.
buf[]byte
ExecParams appends an ExecParams command to the batch. See PgConn.ExecParams for parameter descriptions.
ExecPrepared appends an ExecPrepared e command to the batch. See PgConn.ExecPrepared for parameter descriptions.
func (*PgConn).ExecBatch(ctx context.Context, batch *Batch) *MultiResultReader
BuildFrontendFunc is a function that can be used to create Frontend implementation for connection.
func makeDefaultBuildFrontendFunc(minBufferLen int) BuildFrontendFunc
Config is the settings used to establish a connection to a PostgreSQL server. It must be created by ParseConfig. A
manually initialized Config will cause ConnectConfig to panic.
AfterConnect is called after ValidateConnect. It can be used to set up the connection (e.g. Set session variables
or prepare statements). If this returns an error the connection attempt fails.
BuildFrontendBuildFrontendFuncConnectTimeouttime.DurationDatabasestring
// e.g. net.Dialer.DialContext
Fallbacks[]*FallbackConfig
// host (e.g. localhost) or absolute path to unix domain socket directory (e.g. /private/tmp)
// e.g. net.Resolver.LookupHost
OnNotice is a callback function called when a notice response is received.
OnNotification is a callback function called when a notification from the LISTEN/NOTIFY system is received.
PasswordstringPortuint16
// Run-time parameters to set on connection as session default values (e.g. search_path or application_name)
// nil disables TLS
Userstring
ValidateConnect is called during a connection attempt after a successful authentication with the PostgreSQL server.
It can be used to validate that the server is acceptable. If this returns an error the connection is closed and the next
fallback config is tried. This allows implementing high availability behavior such as libpq does with target_session_attrs.
// Used to enforce created by ParseConfig rule.
Copy returns a deep copy of the config that is safe to use and modify.
The only exception is the TLSConfig field:
according to the tls.Config docs it must not be modified after creation.
func ParseConfig(connString string) (*Config, error)
func (*Config).Copy() *Config
func ConnectConfig(ctx context.Context, config *Config) (pgConn *PgConn, err error)
func connect(ctx context.Context, config *Config, fallbackConfig *FallbackConfig) (*PgConn, error)
FallbackConfig is additional settings to attempt a connection with when the primary Config fails to establish a
network connection. It is used for TLS fallback such as sslmode=prefer and high availability (HA) connections.
// host (e.g. localhost) or path to unix domain socket directory (e.g. /private/tmp)
Portuint16
// nil disables TLS
func expandWithIPs(ctx context.Context, lookupFn LookupFunc, fallbacks []*FallbackConfig) ([]*FallbackConfig, error)
func connect(ctx context.Context, config *Config, fallbackConfig *FallbackConfig) (*PgConn, error)
func expandWithIPs(ctx context.Context, lookupFn LookupFunc, fallbacks []*FallbackConfig) ([]*FallbackConfig, error)
HijackedConn is the result of hijacking a connection.
Due to the necessary exposure of internal implementation details, it is not covered by the semantic versioning
compatibility.
Config*Config
// the underlying TCP or unix domain socket connection
FrontendFrontend
// backend pid
// parameters that have been reported by the server
// key to use to send a cancel query message to the server
TxStatusbyte
func (*PgConn).Hijack() (*HijackedConn, error)
func Construct(hc *HijackedConn) (*PgConn, error)
MultiResultReader is a reader for a command that could return multiple results such as Exec or ExecBatch.
closedboolctxcontext.ContexterrerrorpgConn*PgConnrr*ResultReader
Close closes the MultiResultReader and returns the first error that occurred during the MultiResultReader's use.
NextResult returns advances the MultiResultReader to the next result and returns true if a result is available.
ReadAll reads all available results. Calling ReadAll is mutually exclusive with all other MultiResultReader methods.
ResultReader returns the current ResultReader.
(*T) receiveMessage() (pgproto3.BackendMessage, error)
*T : io.Closer
func (*PgConn).Exec(ctx context.Context, sql string) *MultiResultReader
func (*PgConn).ExecBatch(ctx context.Context, batch *Batch) *MultiResultReader
func (*PgConn).ReceiveResults(ctx context.Context) *MultiResultReader
NoticeHandler is a function that can handle notices received from the PostgreSQL server. Notices can be received at
any time, usually during handling of a query response. The *PgConn is provided so the handler is aware of the origin
of the notice, but it must not invoke any query method. Be aware that this is distinct from LISTEN/NOTIFY
notification.
NotificationHandler is a function that can handle notifications received from the PostgreSQL server. Notifications
can be received at any time, usually during handling of a query response. The *PgConn is provided so the handler is
aware of the origin of the notice, but it must not invoke any query method. Be aware that this is distinct from a
notice event.
PgConn is a low-level PostgreSQL connection handle. It is not safe for concurrent usage.
bufferingReceiveboolbufferingReceiveErrerrorbufferingReceiveMsgpgproto3.BackendMessagebufferingReceiveMuxsync.MutexcleanupDonechan struct{}config*Config
// the underlying TCP or unix domain socket connection
contextWatcher*ctxwatch.ContextWatcherfrontendFrontendmultiResultReaderMultiResultReader
// parameters that have been reported by the server
peekedMsgpgproto3.BackendMessage
// backend pid
resultReaderResultReader
// key to use to send a cancel query message to the server
// One of connStatus* constants
txStatusbyte
Reusable / preallocated resources
// write buffer
CancelRequest sends a cancel request to the PostgreSQL server. It returns an error if unable to deliver the cancel
request, but lack of an error does not ensure that the query was canceled. As specified in the documentation, there
is no way to be sure a query was canceled. See https://www.postgresql.org/docs/11/protocol-flow.html#id-1.10.5.7.9
CleanupDone returns a channel that will be closed after all underlying resources have been cleaned up. A closed
connection is no longer usable, but underlying resources, in particular the net.Conn, may not have finished closing
yet. This is because certain errors such as a context cancellation require that the interrupted function call return
immediately, but the error may also cause the connection to be closed. In these cases the underlying resources are
closed asynchronously.
This is only likely to be useful to connection pools. It gives them a way avoid establishing a new connection while
an old connection is still being cleaned up and thereby exceeding the maximum pool size.
Close closes a connection. It is safe to call Close on a already closed connection. Close attempts a clean close by
sending the exit message to PostgreSQL. However, this could block so ctx is available to limit the time to wait. The
underlying net.Conn.Close() will always be called regardless of any other errors.
Conn returns the underlying net.Conn.
CopyFrom executes the copy command sql and copies all of r to the PostgreSQL server.
Note: context cancellation will only interrupt operations on the underlying PostgreSQL network connection. Reads on r
could still block.
CopyTo executes the copy command sql and copies the results to w.
EscapeString escapes a string such that it can safely be interpolated into a SQL command string. It does not include
the surrounding single quotes.
The current implementation requires that standard_conforming_strings=on and client_encoding="UTF8". If these
conditions are not met an error will be returned. It is possible these restrictions will be lifted in the future.
Exec executes SQL via the PostgreSQL simple query protocol. SQL may contain multiple queries. Execution is
implicitly wrapped in a transaction unless a transaction is already in progress or SQL contains transaction control
statements.
Prefer ExecParams unless executing arbitrary SQL that may contain multiple queries.
ExecBatch executes all the queries in batch in a single round-trip. Execution is implicitly transactional unless a
transaction is already in progress or SQL contains transaction control statements.
ExecParams executes a command via the PostgreSQL extended query protocol.
sql is a SQL command string. It may only contain one query. Parameter substitution is positional using $1, $2, $3,
etc.
paramValues are the parameter values. It must be encoded in the format given by paramFormats.
paramOIDs is a slice of data type OIDs for paramValues. If paramOIDs is nil, the server will infer the data type for
all parameters. Any paramOID element that is 0 that will cause the server to infer the data type for that parameter.
ExecParams will panic if len(paramOIDs) is not 0, 1, or len(paramValues).
paramFormats is a slice of format codes determining for each paramValue column whether it is encoded in text or
binary format. If paramFormats is nil all params are text format. ExecParams will panic if
len(paramFormats) is not 0, 1, or len(paramValues).
resultFormats is a slice of format codes determining for each result column whether it is encoded in text or
binary format. If resultFormats is nil all results will be in text format.
ResultReader must be closed before PgConn can be used again.
ExecPrepared enqueues the execution of a prepared statement via the PostgreSQL extended query protocol.
paramValues are the parameter values. It must be encoded in the format given by paramFormats.
paramFormats is a slice of format codes determining for each paramValue column whether it is encoded in text or
binary format. If paramFormats is nil all params are text format. ExecPrepared will panic if
len(paramFormats) is not 0, 1, or len(paramValues).
resultFormats is a slice of format codes determining for each result column whether it is encoded in text or
binary format. If resultFormats is nil all results will be in text format.
ResultReader must be closed before PgConn can be used again.
Hijack extracts the internal connection data. pgConn must be in an idle state. pgConn is unusable after hijacking.
Hijacking is typically only useful when using pgconn to establish a connection, but taking complete control of the
raw connection after that (e.g. a load balancer or proxy).
Due to the necessary exposure of internal implementation details, it is not covered by the semantic versioning
compatibility.
IsBusy reports if the connection is busy.
IsClosed reports if the connection has been closed.
CleanupDone() can be used to determine if all cleanup has been completed.
PID returns the backend PID.
ParameterStatus returns the value of a parameter reported by the server (e.g.
server_version). Returns an empty string for unknown parameters.
Prepare creates a prepared statement. If the name is empty, the anonymous prepared statement will be used. This
allows Prepare to also to describe statements without creating a server-side prepared statement.
ReceiveMessage receives one wire protocol message from the PostgreSQL server. It must only be used when the
connection is not busy. e.g. It is an error to call ReceiveMessage while reading the result of a query. The messages
are still handled by the core pgconn message handling system so receiving a NotificationResponse will still trigger
the OnNotification callback.
This is a very low level method that requires deep understanding of the PostgreSQL wire protocol to use correctly.
See https://www.postgresql.org/docs/current/protocol.html.
ReceiveResults reads the result that might be returned by Postgres after a SendBytes
(e.a. after sending a CopyDone in a copy-both situation).
This is a very low level method that requires deep understanding of the PostgreSQL wire protocol to use correctly.
See https://www.postgresql.org/docs/current/protocol.html.
SecretKey returns the backend secret key used to send a cancel query message to the server.
SendBytes sends buf to the PostgreSQL server. It must only be used when the connection is not busy. e.g. It is as
error to call SendBytes while reading the result of a query.
This is a very low level method that requires deep understanding of the PostgreSQL wire protocol to use correctly.
See https://www.postgresql.org/docs/current/protocol.html.
TxStatus returns the current TxStatus as reported by the server in the ReadyForQuery message.
Possible return values:
'I' - idle / not in transaction
'T' - in a transaction
'E' - in a failed transaction
See https://www.postgresql.org/docs/current/protocol-message-formats.html.
WaitForNotification waits for a LISTON/NOTIFY message to be received. It returns an error if a notification was not
received.
asyncClose marks the connection as closed and asynchronously sends a cancel query message and closes the underlying
connection.
(*T) execExtendedPrefix(ctx context.Context, paramValues [][]byte) *ResultReader(*T) execExtendedSuffix(buf []byte, result *ResultReader)
lock locks the connection.
peekMessage peeks at the next message without setting up context cancellation.
receiveMessage receives a message without setting up context cancellation
(*T) rxSASLContinue() (*pgproto3.AuthenticationSASLContinue, error)(*T) rxSASLFinal() (*pgproto3.AuthenticationSASLFinal, error)
Perform SCRAM authentication.
(*T) signalMessage() chan struct{}(*T) startTLS(tlsConfig *tls.Config) (err error)(*T) txPasswordMessage(password string) (err error)(*T) unlock()
func Connect(ctx context.Context, connString string) (*PgConn, error)
func ConnectConfig(ctx context.Context, config *Config) (pgConn *PgConn, err error)
func Construct(hc *HijackedConn) (*PgConn, error)
func github.com/jackc/pgx/v4.(*Conn).PgConn() *PgConn
func connect(ctx context.Context, config *Config, fallbackConfig *FallbackConfig) (*PgConn, error)
func ValidateConnectTargetSessionAttrsReadWrite(ctx context.Context, pgConn *PgConn) error
func github.com/jackc/pgconn/stmtcache.New(conn *PgConn, mode int, cap int) stmtcache.Cache
func github.com/jackc/pgconn/stmtcache.NewLRU(conn *PgConn, mode int, cap int) *stmtcache.LRU
func github.com/jackc/pgx/v4.(*Conn).bufferNotifications(_ *PgConn, n *Notification)
Package-Level Functions (total 34, in which 9 are exported)
Connect establishes a connection to a PostgreSQL server using the environment and connString (in URL or DSN format)
to provide configuration. See documention for ParseConfig for details. ctx can be used to cancel a connect attempt.
Connect establishes a connection to a PostgreSQL server using config. config must have been constructed with
ParseConfig. ctx can be used to cancel a connect attempt.
If config.Fallbacks are present they will sequentially be tried in case of error establishing network connection. An
authentication error will terminate the chain of attempts (like libpq:
https://www.postgresql.org/docs/11/libpq-connect.html#LIBPQ-MULTIPLE-HOSTS) and be returned as the error. Otherwise,
if all attempts fail the last error is returned.
Construct created a PgConn from an already established connection to a PostgreSQL server. This is the inverse of
PgConn.Hijack. The connection must be in an idle state.
Due to the necessary exposure of internal implementation details, it is not covered by the semantic versioning
compatibility.
ErrorResponseToPgError converts a wire protocol error message to a *PgError.
NetworkAddress converts a PostgreSQL host and port into network and address suitable for use with
net.Dial.
ParseConfig builds a *Config with similar behavior to the PostgreSQL standard C library libpq. It uses the same
defaults as libpq (e.g. port=5432) and understands most PG* environment variables. ParseConfig closely matches
the parsing behavior of libpq. connString may either be in URL format or keyword = value format (DSN style). See
https://www.postgresql.org/docs/current/libpq-connect.html#LIBPQ-CONNSTRING for details. connString also may be
empty to only read from the environment. If a password is not supplied it will attempt to read the .pgpass file.
# Example DSN
user=jack password=secret host=pg.example.com port=5432 dbname=mydb sslmode=verify-ca
# Example URL
postgres://jack:secret@pg.example.com:5432/mydb?sslmode=verify-ca
The returned *Config may be modified. However, it is strongly recommended that any configuration that can be done
through the connection string be done there. In particular the fields Host, Port, TLSConfig, and Fallbacks can be
interdependent (e.g. TLSConfig needs knowledge of the host to validate the server certificate). These fields should
not be modified individually. They should all be modified or all left unchanged.
ParseConfig supports specifying multiple hosts in similar manner to libpq. Host and port may include comma separated
values that will be tried in order. This can be used as part of a high availability system. See
https://www.postgresql.org/docs/11/libpq-connect.html#LIBPQ-MULTIPLE-HOSTS for more information.
# Example URL
postgres://jack:secret@foo.example.com:5432,bar.example.com:5432/mydb
ParseConfig currently recognizes the following environment variable and their parameter key word equivalents passed
via database URL or DSN:
PGHOST
PGPORT
PGDATABASE
PGUSER
PGPASSWORD
PGPASSFILE
PGSERVICE
PGSERVICEFILE
PGSSLMODE
PGSSLCERT
PGSSLKEY
PGSSLROOTCERT
PGAPPNAME
PGCONNECT_TIMEOUT
PGTARGETSESSIONATTRS
See http://www.postgresql.org/docs/11/static/libpq-envars.html for details on the meaning of environment variables.
See https://www.postgresql.org/docs/11/libpq-connect.html#LIBPQ-PARAMKEYWORDS for parameter key word names. They are
usually but not always the environment variable name downcased and without the "PG" prefix.
Important Security Notes:
ParseConfig tries to match libpq behavior with regard to PGSSLMODE. This includes defaulting to "prefer" behavior if
not set.
See http://www.postgresql.org/docs/11/static/libpq-ssl.html#LIBPQ-SSL-PROTECTION for details on what level of
security each sslmode provides.
The sslmode "prefer" (the default), sslmode "allow", and multiple hosts are implemented via the Fallbacks field of
the Config struct. If TLSConfig is manually changed it will not affect the fallbacks. For example, in the case of
sslmode "prefer" this means it will first try the main Config settings which use TLS, then it will try the fallback
which does not use TLS. This can lead to an unexpected unencrypted connection if the main TLS config is manually
changed later but the unencrypted fallback is present. Ensure there are no stale fallbacks when manually setting
TLCConfig.
Other known differences with libpq:
If a host name resolves into multiple addresses, libpq will try all addresses. pgconn will only try the first.
When multiple hosts are specified, libpq allows them to have different passwords set via the .pgpass file. pgconn
does not.
In addition, ParseConfig accepts the following options:
min_read_buffer_size
The minimum size of the internal read buffer. Default 8192.
servicefile
libpq only reads servicefile from the PGSERVICEFILE environment variable. ParseConfig accepts servicefile as a
part of the connection string.
SafeToRetry checks if the err is guaranteed to have occurred before sending any data to the server.
Timeout checks if err was was caused by a timeout. To be specific, it is true if err is or was caused by a
context.Canceled, context.DeadlineExceeded or an implementer of net.Error where Timeout() is true.
ValidateConnectTargetSessionAttrsReadWrite is an ValidateConnectFunc that implements libpq compatible
target_session_attrs=read-write.
configTLS uses libpq's TLS parameters to construct []*tls.Config. It is
necessary to allow returning multiple TLS configs as sslmode "allow" and
"prefer" allow fallback.
defaultHost attempts to mimic libpq's default host. libpq uses the default unix socket location on *nix and localhost
on Windows. The default socket location is compiled into libpq. Since pgx does not have access to that default it
checks the existence of common locations.
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