postgres

ExampleInitDefault shows the singleton pattern for the default PostgreSQL pool. Call InitDefault once at application startup; subsequent calls are silently ignored (sync.Once).

In this example the singleton was already consumed by a prior test in this binary, so InitDefault is a no-op and returns nil. Default() returns nil because the first initialisation attempt failed (unreachable host).

package main

import (
	"fmt"

	"github.com/phcp-tech/common-library-golang/dbsqlc/postgres"
)

func main() {
	err := postgres.InitDefault(&postgres.Config{
		Host:            "127.0.0.1",
		Port:            "19999",
		Database:        "mydb",
		Username:        "user",
		Password:        "pass",
		MaxOpenConns:    10,
		MaxIdleConns:    2,
		ConnMaxLifetime: 60,
		ConnMaxIdletime: 10,
	})
	fmt.Println(err != nil)                // false — sync.Once no-op, returns nil
	fmt.Println(postgres.Default() != nil) // false — first init failed, instance nil
}

Output:
false
false

ExampleNewPostgres shows the typical usage of NewPostgres. NewPostgres performs an eager connectivity check (show search_path) so callers discover unreachable databases immediately at startup rather than on the first real query. Zero-value pool fields fall back to the dbsqlc package defaults (MaxOpenConns=100, MaxIdleConns=25, ConnMaxLifetime=60min, ConnMaxIdletime=10min).

package main

import (
	"fmt"

	"github.com/phcp-tech/common-library-golang/dbsqlc/postgres"
)

func main() {
	// With an unreachable host the connectivity check fails and an error is returned.
	_, err := postgres.NewPostgres(&postgres.Config{
		Host:     "127.0.0.1",
		Port:     "19999",
		Database: "mydb",
		Username: "user",
		Password: "pass",
	})
	fmt.Println(err != nil) // true — connectivity check failed
}

Output:
true

ExampleNewPostgres_customPool shows how to override the default connection pool settings.

package main

import (
	"fmt"

	"github.com/phcp-tech/common-library-golang/dbsqlc/postgres"
)

func main() {
	_, err := postgres.NewPostgres(&postgres.Config{
		Host:            "127.0.0.1",
		Port:            "19999",
		Database:        "mydb",
		Username:        "user",
		Password:        "pass",
		SearchPath:      "myschema",
		MaxOpenConns:    50,
		MaxIdleConns:    10,
		ConnMaxLifetime: 30, // minutes
		ConnMaxIdletime: 5,  // minutes
	})
	fmt.Println(err != nil) // true — connectivity check failed
}

Output:
true