added db.QueryValue

Author: ungerik

db/config.go

@@ -14,10 +14,10 @@ var (
 )
 
 var (
-	conn = sqldb.ConnectionWithError(
+	globalConn = sqldb.ConnectionWithError(
 		context.Background(),
 		errors.New("database connection not initialized"),
 	)
-	connCtxKey                  int
+	globalConnCtxKey            int
 	serializedTransactionCtxKey int
 )

db/conn.go

@@ -14,23 +14,23 @@ func SetConn(c sqldb.Connection) {
 	if c == nil {
 		panic("must not set nil sqldb.Connection")
 	}
-	conn = c
+	globalConn = c
 }
 
 // Conn returns a non nil sqldb.Connection from ctx
 // or the global connection set with SetConn.
 // The returned connection will use the passed context.
 // See sqldb.Connection.WithContext
 func Conn(ctx context.Context) sqldb.Connection {
-	return ConnDefault(ctx, conn)
+	return ConnDefault(ctx, globalConn)
 }
 
 // ConnDefault returns a non nil sqldb.Connection from ctx
 // or the passed defaultConn.
 // The returned connection will use the passed context.
 // See sqldb.Connection.WithContext
 func ConnDefault(ctx context.Context, defaultConn sqldb.Connection) sqldb.Connection {
-	c, _ := ctx.Value(&connCtxKey).(sqldb.Connection)
+	c, _ := ctx.Value(&globalConnCtxKey).(sqldb.Connection)
 	if c == nil {
 		c = defaultConn
 	}
@@ -45,7 +45,7 @@ func ConnDefault(ctx context.Context, defaultConn sqldb.Connection) sqldb.Connec
 // Passing a nil connection causes Conn(ctx)
 // to return the global connection set with SetConn.
 func ContextWithConn(ctx context.Context, conn sqldb.Connection) context.Context {
-	return context.WithValue(ctx, &connCtxKey, conn)
+	return context.WithValue(ctx, &globalConnCtxKey, conn)
 }
 
 // ContextWithoutCancel returns a new context that inherits

db/querystruct.go renamed to db/query.go

@@ -5,10 +5,41 @@ import (
 	"errors"
 	"fmt"
 	"reflect"
+	"time"
 
 	"github.com/domonda/go-sqldb"
 )
 
+// Now returns the result of the SQL now()
+// function for the current connection.
+// Useful for getting the timestamp of a
+// SQL transaction for use in Go code.
+func Now(ctx context.Context) (time.Time, error) {
+	return Conn(ctx).Now()
+}
+
+// Exec executes a query with optional args.
+func Exec(ctx context.Context, query string, args ...any) error {
+	return Conn(ctx).Exec(query, args...)
+}
+
+// QueryRow queries a single row and returns a RowScanner for the results.
+func QueryRow(ctx context.Context, query string, args ...any) sqldb.RowScanner {
+	return Conn(ctx).QueryRow(query, args...)
+}
+
+// QueryRows queries multiple rows and returns a RowsScanner for the results.
+func QueryRows(ctx context.Context, query string, args ...any) sqldb.RowsScanner {
+	return Conn(ctx).QueryRows(query, args...)
+}
+
+// QueryValue queries a single value of type T.
+func QueryValue[T any](ctx context.Context, query string, args ...any) (T, error) {
+	var val T
+	err := Conn(ctx).QueryRow(query, args...).Scan(&val)
+	return val, err
+}
+
 // QueryStruct uses the passed pkValues to query a table row
 // and scan it into a struct of type S that must have tagged fields
 // with primary key flags to identify the primary key column names

db/transaction.go

@@ -51,7 +51,7 @@ func DebugNoTransaction(ctx context.Context, nonTxFunc func(context.Context) err
 // Recovered panics are re-paniced and rollback errors after a panic are logged with ErrLogger.
 func IsolatedTransaction(ctx context.Context, txFunc func(context.Context) error) error {
 	return sqldb.IsolatedTransaction(Conn(ctx), nil, func(tx sqldb.Connection) error {
-		return txFunc(context.WithValue(ctx, &connCtxKey, tx))
+		return txFunc(context.WithValue(ctx, &globalConnCtxKey, tx))
 	})
 }
 
@@ -64,7 +64,7 @@ func IsolatedTransaction(ctx context.Context, txFunc func(context.Context) error
 // Recovered panics are re-paniced and rollback errors after a panic are logged with sqldb.ErrLogger.
 func Transaction(ctx context.Context, txFunc func(context.Context) error) error {
 	return sqldb.Transaction(Conn(ctx), nil, func(tx sqldb.Connection) error {
-		return txFunc(context.WithValue(ctx, &connCtxKey, tx))
+		return txFunc(context.WithValue(ctx, &globalConnCtxKey, tx))
 	})
 }
 
@@ -135,7 +135,7 @@ func SerializedTransaction(ctx context.Context, txFunc func(context.Context) err
 // Recovered panics are re-paniced and rollback errors after a panic are logged with sqldb.ErrLogger.
 func TransactionOpts(ctx context.Context, opts *sql.TxOptions, txFunc func(context.Context) error) error {
 	return sqldb.Transaction(Conn(ctx), opts, func(tx sqldb.Connection) error {
-		return txFunc(context.WithValue(ctx, &connCtxKey, tx))
+		return txFunc(context.WithValue(ctx, &globalConnCtxKey, tx))
 	})
 }
 
@@ -149,7 +149,7 @@ func TransactionOpts(ctx context.Context, opts *sql.TxOptions, txFunc func(conte
 func TransactionReadOnly(ctx context.Context, txFunc func(context.Context) error) error {
 	opts := sql.TxOptions{ReadOnly: true}
 	return sqldb.Transaction(Conn(ctx), &opts, func(tx sqldb.Connection) error {
-		return txFunc(context.WithValue(ctx, &connCtxKey, tx))
+		return txFunc(context.WithValue(ctx, &globalConnCtxKey, tx))
 	})
 }
 

db/transaction_test.go

@@ -10,7 +10,7 @@ import (
 )
 
 func TestSerializedTransaction(t *testing.T) {
-	conn = mockconn.New(context.Background(), os.Stdout, nil)
+	globalConn = mockconn.New(context.Background(), os.Stdout, nil)
 
 	expectSerialized := func(ctx context.Context) error {
 		if !Conn(ctx).IsTransaction() {
@@ -64,7 +64,7 @@ func TestSerializedTransaction(t *testing.T) {
 }
 
 func TestTransaction(t *testing.T) {
-	conn = mockconn.New(context.Background(), os.Stdout, nil)
+	globalConn = mockconn.New(context.Background(), os.Stdout, nil)
 
 	expectNonSerialized := func(ctx context.Context) error {
 		if !Conn(ctx).IsTransaction() {