cli/sql: new parameter --watch to repeat the -e statements

pkg/cli/cli_test.go

@@ -625,6 +625,24 @@ func Example_sql() {
 	// invalid syntax
 }
 
+func Example_sql_watch() {
+	c := newCLITest(cliTestParams{})
+	defer c.cleanup()
+
+	c.RunWithArgs([]string{`sql`, `-e`, `create table d(x int); insert into d values(3)`})
+	c.RunWithArgs([]string{`sql`, `--watch`, `.1s`, `-e`, `update d set x=x-1 returning 1/x as dec`})
+
+	// Output:
+	// sql -e create table d(x int); insert into d values(3)
+	// INSERT 1
+	// sql --watch .1s -e update d set x=x-1 returning 1/x as dec
+	// dec
+	// 0.5
+	// dec
+	// 1
+	// pq: division by zero
+}
+
 func Example_sql_format() {
 	c := newCLITest(cliTestParams{})
 	defer c.cleanup()

pkg/cli/cliflags/flags.go

@@ -238,6 +238,14 @@ with a non-zero status code and further statements are not executed. The
 results of each SQL statement are printed on the standard output.`,
 	}
 
+	Watch = FlagInfo{
+		Name: "watch",
+		Description: `
+Repeat the SQL statement(s) specified with --execute
+with the specified period. The client will stop watching
+if an execution of the SQL statement(s) fail.`,
+	}
+
 	EchoSQL = FlagInfo{
 		Name: "echo-sql",
 		Description: `

pkg/cli/context.go

@@ -83,6 +83,7 @@ func initCLIDefaults() {
 
 	sqlCtx.setStmts = nil
 	sqlCtx.execStmts = nil
+	sqlCtx.repeatDelay = 0
 	sqlCtx.safeUpdates = false
 	sqlCtx.showTimes = false
 	sqlCtx.debugMode = false
@@ -217,6 +218,11 @@ var sqlCtx = struct {
 	// execStmts is a list of statements to execute.
 	execStmts statementsValue
 
+	// repeatDelay indicates that the execStmts should be "watched"
+	// at the specified time interval. Zero disables
+	// the watch.
+	repeatDelay time.Duration
+
 	// safeUpdates indicates whether to set sql_safe_updates in the CLI
 	// shell.
 	safeUpdates bool

pkg/cli/flags.go

@@ -527,6 +527,7 @@ func init() {
 		f := cmd.Flags()
 		VarFlag(f, &sqlCtx.setStmts, cliflags.Set)
 		VarFlag(f, &sqlCtx.execStmts, cliflags.Execute)
+		DurationFlag(f, &sqlCtx.repeatDelay, cliflags.Watch, sqlCtx.repeatDelay)
 		BoolFlag(f, &sqlCtx.safeUpdates, cliflags.SafeUpdates, sqlCtx.safeUpdates)
 		BoolFlag(f, &sqlCtx.debugMode, cliflags.CliDebugMode, sqlCtx.debugMode)
 	}

pkg/cli/sql.go

@@ -24,6 +24,7 @@ import (
 	"sort"
 	"strconv"
 	"strings"
+	"time"
 
 	"github.com/cockroachdb/cockroach/pkg/base"
 	"github.com/cockroachdb/cockroach/pkg/cli/cliflags"
@@ -1389,22 +1390,31 @@ func runInteractive(conn *sqlConn) (exitErr error) {
 // runOneStatement executes one statement and terminates
 // on error.
 func (c *cliState) runStatements(stmts []string) error {
-	for i, stmt := range stmts {
-		// We do not use the logic from doRunStatement here
-		// because we need a different error handling mechanism:
-		// the error, if any, must not be printed to stderr if
-		// we are returning directly.
-		c.exitErr = runQueryAndFormatResults(c.conn, os.Stdout, makeQuery(stmt))
-		if c.exitErr != nil {
-			if !c.errExit && i < len(stmts)-1 {
-				// Print the error now because we don't get a chance later.
-				fmt.Fprintln(stderr, c.exitErr)
-				maybeShowErrorDetails(stderr, c.exitErr, false)
-			}
-			if c.errExit {
-				break
+	for {
+		for i, stmt := range stmts {
+			// We do not use the logic from doRunStatement here
+			// because we need a different error handling mechanism:
+			// the error, if any, must not be printed to stderr if
+			// we are returning directly.
+			c.exitErr = runQueryAndFormatResults(c.conn, os.Stdout, makeQuery(stmt))
+			if c.exitErr != nil {
+				if !c.errExit && i < len(stmts)-1 {
+					// Print the error now because we don't get a chance later.
+					fmt.Fprintln(stderr, c.exitErr)
+					maybeShowErrorDetails(stderr, c.exitErr, false)
+				}
+				if c.errExit {
+					break
+				}
 			}
 		}
+		// If --watch was specified and no error was encountered,
+		// repeat.
+		if sqlCtx.repeatDelay > 0 && c.exitErr == nil {
+			time.Sleep(sqlCtx.repeatDelay)
+			continue
+		}
+		break
 	}
 
 	if c.exitErr != nil {