pgxpool

package
Version: v5.2.0 Latest Latest
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Published: Dec 6, 2022 License: MIT Imports: 11 Imported by: 166

Documentation

Overview

Package pgxpool is a concurrency-safe connection pool for pgx.

pgxpool implements a nearly identical interface to pgx connections.

Creating a Pool

The primary way of creating a pool is with `pgxpool.New`.

pool, err := pgxpool.New(context.Background(), os.Getenv("DATABASE_URL"))

The database connection string can be in URL or DSN format. PostgreSQL settings, pgx settings, and pool settings can be specified here. In addition, a config struct can be created by `ParseConfig` and modified before establishing the connection with `ConnectConfig`.

config, err := pgxpool.ParseConfig(os.Getenv("DATABASE_URL"))
if err != nil {
    // ...
}
config.AfterConnect = func(ctx context.Context, conn *pgx.Conn) error {
    // do something with every new connection
}

pool, err := pgxpool.NewWithConfig(context.Background(), config)

A pool returns without waiting for any connections to be established. Acquire a connection immediately after creating the pool to check if a connection can successfully be established.

Index

Constants

This section is empty.

Variables

This section is empty.

Functions

This section is empty.

Types

type Config

type Config struct {
	ConnConfig *pgx.ConnConfig

	// BeforeConnect is called before a new connection is made. It is passed a copy of the underlying pgx.ConnConfig and
	// will not impact any existing open connections.
	BeforeConnect func(context.Context, *pgx.ConnConfig) error

	// AfterConnect is called after a connection is established, but before it is added to the pool.
	AfterConnect func(context.Context, *pgx.Conn) error

	// BeforeAcquire is called before a connection is acquired from the pool. It must return true to allow the
	// acquision or false to indicate that the connection should be destroyed and a different connection should be
	// acquired.
	BeforeAcquire func(context.Context, *pgx.Conn) bool

	// AfterRelease is called after a connection is released, but before it is returned to the pool. It must return true to
	// return the connection to the pool or false to destroy the connection.
	AfterRelease func(*pgx.Conn) bool

	// MaxConnLifetime is the duration since creation after which a connection will be automatically closed.
	MaxConnLifetime time.Duration

	// MaxConnLifetimeJitter is the duration after MaxConnLifetime to randomly decide to close a connection.
	// This helps prevent all connections from being closed at the exact same time, starving the pool.
	MaxConnLifetimeJitter time.Duration

	// MaxConnIdleTime is the duration after which an idle connection will be automatically closed by the health check.
	MaxConnIdleTime time.Duration

	// MaxConns is the maximum size of the pool. The default is the greater of 4 or runtime.NumCPU().
	MaxConns int32

	// MinConns is the minimum size of the pool. After connection closes, the pool might dip below MinConns. A low
	// number of MinConns might mean the pool is empty after MaxConnLifetime until the health check has a chance
	// to create new connections.
	MinConns int32

	// HealthCheckPeriod is the duration between checks of the health of idle connections.
	HealthCheckPeriod time.Duration
	// contains filtered or unexported fields
}

Config is the configuration struct for creating a pool. It must be created by ParseConfig and then it can be modified. A manually initialized ConnConfig will cause ConnectConfig to panic.

func ParseConfig

func ParseConfig(connString string) (*Config, error)

ParseConfig builds a Config from connString. It parses connString with the same behavior as pgx.ParseConfig with the addition of the following variables:

pool_max_conns: integer greater than 0 pool_min_conns: integer 0 or greater pool_max_conn_lifetime: duration string pool_max_conn_idle_time: duration string pool_health_check_period: duration string pool_max_conn_lifetime_jitter: duration string

See Config for definitions of these arguments.

# Example DSN
user=jack password=secret host=pg.example.com port=5432 dbname=mydb sslmode=verify-ca pool_max_conns=10

# Example URL
postgres://jack:secret@pg.example.com:5432/mydb?sslmode=verify-ca&pool_max_conns=10

func (*Config) ConnString

func (c *Config) ConnString() string

ConnString returns the connection string as parsed by pgxpool.ParseConfig into pgxpool.Config.

func (*Config) Copy

func (c *Config) Copy() *Config

Copy returns a deep copy of the config that is safe to use and modify. The only exception is the tls.Config: according to the tls.Config docs it must not be modified after creation.

type Conn

type Conn struct {
	// contains filtered or unexported fields
}

Conn is an acquired *pgx.Conn from a Pool.

func (*Conn) Begin

func (c *Conn) Begin(ctx context.Context) (pgx.Tx, error)

Begin starts a transaction block from the *Conn without explicitly setting a transaction mode (see BeginTx with TxOptions if transaction mode is required).

func (*Conn) BeginTx

func (c *Conn) BeginTx(ctx context.Context, txOptions pgx.TxOptions) (pgx.Tx, error)

BeginTx starts a transaction block from the *Conn with txOptions determining the transaction mode.

func (*Conn) Conn

func (c *Conn) Conn() *pgx.Conn

func (*Conn) CopyFrom

func (c *Conn) CopyFrom(ctx context.Context, tableName pgx.Identifier, columnNames []string, rowSrc pgx.CopyFromSource) (int64, error)

func (*Conn) Exec

func (c *Conn) Exec(ctx context.Context, sql string, arguments ...any) (pgconn.CommandTag, error)

func (*Conn) Hijack

func (c *Conn) Hijack() *pgx.Conn

Hijack assumes ownership of the connection from the pool. Caller is responsible for closing the connection. Hijack will panic if called on an already released or hijacked connection.

func (*Conn) Ping

func (c *Conn) Ping(ctx context.Context) error

func (*Conn) Query

func (c *Conn) Query(ctx context.Context, sql string, args ...any) (pgx.Rows, error)

func (*Conn) QueryRow

func (c *Conn) QueryRow(ctx context.Context, sql string, args ...any) pgx.Row

func (*Conn) Release

func (c *Conn) Release()

Release returns c to the pool it was acquired from. Once Release has been called, other methods must not be called. However, it is safe to call Release multiple times. Subsequent calls after the first will be ignored.

func (*Conn) SendBatch

func (c *Conn) SendBatch(ctx context.Context, b *pgx.Batch) pgx.BatchResults

type Pool

type Pool struct {
	// contains filtered or unexported fields
}

Pool allows for connection reuse.

func New

func New(ctx context.Context, connString string) (*Pool, error)

New creates a new Pool. See ParseConfig for information on connString format.

func NewWithConfig

func NewWithConfig(ctx context.Context, config *Config) (*Pool, error)

NewWithConfig creates a new Pool. config must have been created by ParseConfig.

func (*Pool) Acquire

func (p *Pool) Acquire(ctx context.Context) (*Conn, error)

Acquire returns a connection (*Conn) from the Pool

func (*Pool) AcquireAllIdle

func (p *Pool) AcquireAllIdle(ctx context.Context) []*Conn

AcquireAllIdle atomically acquires all currently idle connections. Its intended use is for health check and keep-alive functionality. It does not update pool statistics.

func (*Pool) AcquireFunc

func (p *Pool) AcquireFunc(ctx context.Context, f func(*Conn) error) error

AcquireFunc acquires a *Conn and calls f with that *Conn. ctx will only affect the Acquire. It has no effect on the call of f. The return value is either an error acquiring the *Conn or the return value of f. The *Conn is automatically released after the call of f.

func (*Pool) Begin

func (p *Pool) Begin(ctx context.Context) (pgx.Tx, error)

Begin acquires a connection from the Pool and starts a transaction. Unlike database/sql, the context only affects the begin command. i.e. there is no auto-rollback on context cancellation. Begin initiates a transaction block without explicitly setting a transaction mode for the block (see BeginTx with TxOptions if transaction mode is required). *pgxpool.Tx is returned, which implements the pgx.Tx interface. Commit or Rollback must be called on the returned transaction to finalize the transaction block.

func (*Pool) BeginTx

func (p *Pool) BeginTx(ctx context.Context, txOptions pgx.TxOptions) (pgx.Tx, error)

BeginTx acquires a connection from the Pool and starts a transaction with pgx.TxOptions determining the transaction mode. Unlike database/sql, the context only affects the begin command. i.e. there is no auto-rollback on context cancellation. *pgxpool.Tx is returned, which implements the pgx.Tx interface. Commit or Rollback must be called on the returned transaction to finalize the transaction block.

func (*Pool) Close

func (p *Pool) Close()

Close closes all connections in the pool and rejects future Acquire calls. Blocks until all connections are returned to pool and closed.

func (*Pool) Config

func (p *Pool) Config() *Config

Config returns a copy of config that was used to initialize this pool.

func (*Pool) CopyFrom

func (p *Pool) CopyFrom(ctx context.Context, tableName pgx.Identifier, columnNames []string, rowSrc pgx.CopyFromSource) (int64, error)

func (*Pool) Exec

func (p *Pool) Exec(ctx context.Context, sql string, arguments ...any) (pgconn.CommandTag, error)

Exec acquires a connection from the Pool and executes the given SQL. SQL can be either a prepared statement name or an SQL string. Arguments should be referenced positionally from the SQL string as $1, $2, etc. The acquired connection is returned to the pool when the Exec function returns.

func (*Pool) Ping

func (p *Pool) Ping(ctx context.Context) error

Ping acquires a connection from the Pool and executes an empty sql statement against it. If the sql returns without error, the database Ping is considered successful, otherwise, the error is returned.

func (*Pool) Query

func (p *Pool) Query(ctx context.Context, sql string, args ...any) (pgx.Rows, error)

Query acquires a connection and executes a query that returns pgx.Rows. Arguments should be referenced positionally from the SQL string as $1, $2, etc. See pgx.Rows documentation to close the returned Rows and return the acquired connection to the Pool.

If there is an error, the returned pgx.Rows will be returned in an error state. If preferred, ignore the error returned from Query and handle errors using the returned pgx.Rows.

For extra control over how the query is executed, the types QuerySimpleProtocol, QueryResultFormats, and QueryResultFormatsByOID may be used as the first args to control exactly how the query is executed. This is rarely needed. See the documentation for those types for details.

func (*Pool) QueryRow

func (p *Pool) QueryRow(ctx context.Context, sql string, args ...any) pgx.Row

QueryRow acquires a connection and executes a query that is expected to return at most one row (pgx.Row). Errors are deferred until pgx.Row's Scan method is called. If the query selects no rows, pgx.Row's Scan will return ErrNoRows. Otherwise, pgx.Row's Scan scans the first selected row and discards the rest. The acquired connection is returned to the Pool when pgx.Row's Scan method is called.

Arguments should be referenced positionally from the SQL string as $1, $2, etc.

For extra control over how the query is executed, the types QuerySimpleProtocol, QueryResultFormats, and QueryResultFormatsByOID may be used as the first args to control exactly how the query is executed. This is rarely needed. See the documentation for those types for details.

func (*Pool) Reset

func (p *Pool) Reset()

Reset closes all connections, but leaves the pool open. It is intended for use when an error is detected that would disrupt all connections (such as a network interruption or a server state change).

It is safe to reset a pool while connections are checked out. Those connections will be closed when they are returned to the pool.

func (*Pool) SendBatch

func (p *Pool) SendBatch(ctx context.Context, b *pgx.Batch) pgx.BatchResults

func (*Pool) Stat

func (p *Pool) Stat() *Stat

Stat returns a pgxpool.Stat struct with a snapshot of Pool statistics.

type Stat

type Stat struct {
	// contains filtered or unexported fields
}

Stat is a snapshot of Pool statistics.

func (*Stat) AcquireCount

func (s *Stat) AcquireCount() int64

AcquireCount returns the cumulative count of successful acquires from the pool.

func (*Stat) AcquireDuration

func (s *Stat) AcquireDuration() time.Duration

AcquireDuration returns the total duration of all successful acquires from the pool.

func (*Stat) AcquiredConns

func (s *Stat) AcquiredConns() int32

AcquiredConns returns the number of currently acquired connections in the pool.

func (*Stat) CanceledAcquireCount

func (s *Stat) CanceledAcquireCount() int64

CanceledAcquireCount returns the cumulative count of acquires from the pool that were canceled by a context.

func (*Stat) ConstructingConns

func (s *Stat) ConstructingConns() int32

ConstructingConns returns the number of conns with construction in progress in the pool.

func (*Stat) EmptyAcquireCount

func (s *Stat) EmptyAcquireCount() int64

EmptyAcquireCount returns the cumulative count of successful acquires from the pool that waited for a resource to be released or constructed because the pool was empty.

func (*Stat) IdleConns

func (s *Stat) IdleConns() int32

IdleConns returns the number of currently idle conns in the pool.

func (*Stat) MaxConns

func (s *Stat) MaxConns() int32

MaxConns returns the maximum size of the pool.

func (*Stat) MaxIdleDestroyCount

func (s *Stat) MaxIdleDestroyCount() int64

MaxIdleDestroyCount returns the cumulative count of connections destroyed because they exceeded MaxConnIdleTime.

func (*Stat) MaxLifetimeDestroyCount

func (s *Stat) MaxLifetimeDestroyCount() int64

MaxLifetimeDestroyCount returns the cumulative count of connections destroyed because they exceeded MaxConnLifetime.

func (*Stat) NewConnsCount

func (s *Stat) NewConnsCount() int64

NewConnsCount returns the cumulative count of new connections opened.

func (*Stat) TotalConns

func (s *Stat) TotalConns() int32

TotalConns returns the total number of resources currently in the pool. The value is the sum of ConstructingConns, AcquiredConns, and IdleConns.

type Tx

type Tx struct {
	// contains filtered or unexported fields
}

Tx represents a database transaction acquired from a Pool.

func (*Tx) Begin

func (tx *Tx) Begin(ctx context.Context) (pgx.Tx, error)

Begin starts a pseudo nested transaction implemented with a savepoint.

func (*Tx) Commit

func (tx *Tx) Commit(ctx context.Context) error

Commit commits the transaction and returns the associated connection back to the Pool. Commit will return ErrTxClosed if the Tx is already closed, but is otherwise safe to call multiple times. If the commit fails with a rollback status (e.g. the transaction was already in a broken state) then ErrTxCommitRollback will be returned.

func (*Tx) Conn

func (tx *Tx) Conn() *pgx.Conn

func (*Tx) CopyFrom

func (tx *Tx) CopyFrom(ctx context.Context, tableName pgx.Identifier, columnNames []string, rowSrc pgx.CopyFromSource) (int64, error)

func (*Tx) Exec

func (tx *Tx) Exec(ctx context.Context, sql string, arguments ...any) (pgconn.CommandTag, error)

func (*Tx) LargeObjects

func (tx *Tx) LargeObjects() pgx.LargeObjects

func (*Tx) Prepare

func (tx *Tx) Prepare(ctx context.Context, name, sql string) (*pgconn.StatementDescription, error)

Prepare creates a prepared statement with name and sql. If the name is empty, an anonymous prepared statement will be used. sql can contain placeholders for bound parameters. These placeholders are referenced positionally as $1, $2, etc.

Prepare is idempotent; i.e. it is safe to call Prepare multiple times with the same name and sql arguments. This allows a code path to Prepare and Query/Exec without needing to first check whether the statement has already been prepared.

func (*Tx) Query

func (tx *Tx) Query(ctx context.Context, sql string, args ...any) (pgx.Rows, error)

func (*Tx) QueryRow

func (tx *Tx) QueryRow(ctx context.Context, sql string, args ...any) pgx.Row

func (*Tx) Rollback

func (tx *Tx) Rollback(ctx context.Context) error

Rollback rolls back the transaction and returns the associated connection back to the Pool. Rollback will return ErrTxClosed if the Tx is already closed, but is otherwise safe to call multiple times. Hence, defer tx.Rollback() is safe even if tx.Commit() will be called first in a non-error condition.

func (*Tx) SendBatch

func (tx *Tx) SendBatch(ctx context.Context, b *pgx.Batch) pgx.BatchResults

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