conn_go18.go

// +build go1.8

package clickhouse

import (
	"context"
	"database/sql/driver"
	"fmt"
	"io/ioutil"
	"strings"
)

// pingExpectedPrefix represents expected answer for "SELECT 1" query
const pingExpectedPrefix = "1"

// Ping implements the driver.Pinger
func (c *conn) Ping(ctx context.Context) error {
	if c.transport == nil {
		return ErrTransportNil
	}

	req, err := c.buildRequest(ctx, "select 1", nil)
	if err != nil {
		return err
	}

	respBody, err := c.doRequest(ctx, req)
	defer func() {
		c.cancel = nil
	}()
	if err != nil {
		return err
	}

	// Close response body to enable connection reuse
	defer respBody.Close()

	// drain the response body to check if we got expected `1`
	resp, err := ioutil.ReadAll(respBody)
	if err != nil {
		return fmt.Errorf("ping: failed to read the response: %w", err)
	}
	if !strings.HasPrefix(string(resp), pingExpectedPrefix) {
		return fmt.Errorf("ping: failed to get expected result (1), got '%s' instead", string(resp))
	}
	return nil
}

// BeginTx implements the driver.ConnBeginTx
func (c *conn) BeginTx(ctx context.Context, opts driver.TxOptions) (driver.Tx, error) {
	return c.beginTx(ctx)
}

// PrepareContext implements the driver.ConnPrepareContext
func (c *conn) PrepareContext(_ context.Context, query string) (driver.Stmt, error) {
	return c.prepare(query)
}

// ExecContext implements the driver.ExecerContext
func (c *conn) ExecContext(ctx context.Context, query string, args []driver.NamedValue) (driver.Result, error) {
	values, err := namedValueToValue(args)
	if err != nil {
		return nil, err
	}
	return c.exec(ctx, query, values)
}

// QueryContext implements the driver.QueryerContext
func (c *conn) QueryContext(ctx context.Context, query string, args []driver.NamedValue) (driver.Rows, error) {
	values, err := namedValueToValue(args)
	if err != nil {
		return nil, err
	}
	return c.query(ctx, query, values)
}

func namedValueToValue(named []driver.NamedValue) ([]driver.Value, error) {
	dargs := make([]driver.Value, len(named))
	for n, param := range named {
		if len(param.Name) > 0 {
			// TODO: support the use of Named Parameters #561
			return nil, ErrNameParams
		}
		dargs[n] = param.Value
	}
	return dargs, nil
}