Add .timer command.

cmd/genji/shell/command.go

@@ -10,6 +10,7 @@ import (
 	"strings"
 
 	"github.com/cockroachdb/errors"
+
 	"github.com/genjidb/genji"
 	"github.com/genjidb/genji/cmd/genji/dbutil"
 	"github.com/genjidb/genji/cmd/genji/doc"
@@ -84,6 +85,12 @@ var commands = []command{
 		DisplayName: ".import",
 		Description: "Import data from a file. Only supported type is 'csv'",
 	},
+	{
+		Name:        ".timer",
+		Options:     "[on|off]",
+		DisplayName: ".timer",
+		Description: "Display the execution time after each query or hide it.",
+	},
 }
 
 func getUsage(cmdName string) string {

cmd/genji/shell/shell.go

@@ -10,17 +10,19 @@ import (
 	"strings"
 	"sync"
 	"syscall"
+	"time"
 
 	"github.com/agnivade/levenshtein"
 	"github.com/c-bata/go-prompt"
 	"github.com/cockroachdb/errors"
+	"go.uber.org/multierr"
+	"golang.org/x/sync/errgroup"
+
 	"github.com/genjidb/genji"
 	"github.com/genjidb/genji/cmd/genji/dbutil"
 	"github.com/genjidb/genji/document"
 	"github.com/genjidb/genji/internal/sql/parser"
 	"github.com/genjidb/genji/types"
-	"go.uber.org/multierr"
-	"golang.org/x/sync/errgroup"
 )
 
 const (
@@ -45,6 +47,8 @@ type Shell struct {
 	livePrefix string
 	multiLine  bool
 
+	showTime bool
+
 	history []string
 
 	cmdSuggestions []prompt.Suggest
@@ -173,6 +177,8 @@ func (sh *Shell) runExecutor(ctx context.Context, promptExecCh chan string) erro
 		case <-ctx.Done():
 			return ctx.Err()
 		case input := <-promptExecCh:
+			showTime := sh.showTime
+			start := time.Now().UTC()
 			err := sh.executeInput(sh.getExecContext(ctx), input)
 			// if the context has been canceled
 			// there is no way to tell at this point
@@ -189,12 +195,34 @@ func (sh *Shell) runExecutor(ctx context.Context, promptExecCh chan string) erro
 			}
 			if err != nil {
 				fmt.Println(err)
+				continue
+			}
+
+			// even if showtime is true, ensure it's a query, and it was executed.
+			if showTime && !strings.HasPrefix(input, ".") && strings.HasSuffix(input, ";") {
+				displayTime(start)
 			}
 		case promptExecCh <- "":
 		}
 	}
 }
 
+// displayTime shows execution time of a query.
+func displayTime(start time.Time) {
+	unit := "s"
+	multiplier := 1.0
+	precision := 3
+	completed := time.Since(start)
+	// under a second print in ms unit.
+	if completed.Seconds() < 1 {
+		unit = "ms"
+		multiplier = 1000.
+		precision = 0
+	}
+
+	fmt.Printf("Time: %.*f%s\n", precision, completed.Seconds()*multiplier, unit)
+}
+
 // runPrompt is a stateless function that displays a prompt to the user.
 // User input is sent to the execCh channel which must deal with parsing and error handling.
 // Once the execution of the user input is done by the reader of the channel, it must
@@ -415,6 +443,13 @@ func (sh *Shell) runCommand(ctx context.Context, in string) error {
 	in = strings.TrimSuffix(in, ";")
 	cmd := strings.Fields(in)
 	switch cmd[0] {
+	case ".timer":
+		if len(cmd) != 2 || (cmd[1] != "on" && cmd[1] != "off") {
+			return fmt.Errorf(getUsage(".timer"))
+		}
+
+		sh.showTime = cmd[1] == "on"
+		return nil
 	case ".help", "help":
 		return runHelpCmd()
 	case ".tables":