DOC-4560 pipelines/transactions example (#3202)

* DOC-4560 basic transaction example

* DOC-4560 added pipe/transaction examples

doctests/pipe_trans_example_test.go

@@ -0,0 +1,180 @@
+// EXAMPLE: pipe_trans_tutorial
+// HIDE_START
+package example_commands_test
+
+import (
+	"context"
+	"fmt"
+
+	"github.com/redis/go-redis/v9"
+)
+
+// HIDE_END
+
+func ExampleClient_transactions() {
+	ctx := context.Background()
+
+	rdb := redis.NewClient(&redis.Options{
+		Addr:     "localhost:6379",
+		Password: "", // no password docs
+		DB:       0,  // use default DB
+	})
+	// REMOVE_START
+	for i := 0; i < 5; i++ {
+		rdb.Del(ctx, fmt.Sprintf("seat:%d", i))
+	}
+
+	rdb.Del(ctx, "counter:1", "counter:2", "counter:3", "shellpath")
+	// REMOVE_END
+
+	// STEP_START basic_pipe
+	pipe := rdb.Pipeline()
+
+	for i := 0; i < 5; i++ {
+		pipe.Set(ctx, fmt.Sprintf("seat:%v", i), fmt.Sprintf("#%v", i), 0)
+	}
+
+	cmds, err := pipe.Exec(ctx)
+
+	if err != nil {
+		panic(err)
+	}
+
+	for _, c := range cmds {
+		fmt.Printf("%v;", c.(*redis.StatusCmd).Val())
+	}
+
+	fmt.Println("")
+	// >>> OK;OK;OK;OK;OK;
+
+	pipe = rdb.Pipeline()
+
+	get0Result := pipe.Get(ctx, "seat:0")
+	get3Result := pipe.Get(ctx, "seat:3")
+	get4Result := pipe.Get(ctx, "seat:4")
+
+	cmds, err = pipe.Exec(ctx)
+
+	// The results are available only after the pipeline
+	// has finished executing.
+	fmt.Println(get0Result.Val()) // >>> #0
+	fmt.Println(get3Result.Val()) // >>> #3
+	fmt.Println(get4Result.Val()) // >>> #4
+	// STEP_END
+
+	// STEP_START basic_pipe_pipelined
+	var pd0Result *redis.StatusCmd
+	var pd3Result *redis.StatusCmd
+	var pd4Result *redis.StatusCmd
+
+	cmds, err = rdb.Pipelined(ctx, func(pipe redis.Pipeliner) error {
+		pd0Result = (*redis.StatusCmd)(pipe.Get(ctx, "seat:0"))
+		pd3Result = (*redis.StatusCmd)(pipe.Get(ctx, "seat:3"))
+		pd4Result = (*redis.StatusCmd)(pipe.Get(ctx, "seat:4"))
+		return nil
+	})
+
+	if err != nil {
+		panic(err)
+	}
+
+	// The results are available only after the pipeline
+	// has finished executing.
+	fmt.Println(pd0Result.Val()) // >>> #0
+	fmt.Println(pd3Result.Val()) // >>> #3
+	fmt.Println(pd4Result.Val()) // >>> #4
+	// STEP_END
+
+	// STEP_START basic_trans
+	trans := rdb.TxPipeline()
+
+	trans.IncrBy(ctx, "counter:1", 1)
+	trans.IncrBy(ctx, "counter:2", 2)
+	trans.IncrBy(ctx, "counter:3", 3)
+
+	cmds, err = trans.Exec(ctx)
+
+	for _, c := range cmds {
+		fmt.Println(c.(*redis.IntCmd).Val())
+	}
+	// >>> 1
+	// >>> 2
+	// >>> 3
+	// STEP_END
+
+	// STEP_START basic_trans_txpipelined
+	var tx1Result *redis.IntCmd
+	var tx2Result *redis.IntCmd
+	var tx3Result *redis.IntCmd
+
+	cmds, err = rdb.TxPipelined(ctx, func(trans redis.Pipeliner) error {
+		tx1Result = trans.IncrBy(ctx, "counter:1", 1)
+		tx2Result = trans.IncrBy(ctx, "counter:2", 2)
+		tx3Result = trans.IncrBy(ctx, "counter:3", 3)
+		return nil
+	})
+
+	if err != nil {
+		panic(err)
+	}
+
+	fmt.Println(tx1Result.Val()) // >>> 2
+	fmt.Println(tx2Result.Val()) // >>> 4
+	fmt.Println(tx3Result.Val()) // >>> 6
+	// STEP_END
+
+	// STEP_START trans_watch
+	// Set initial value of `shellpath`.
+	rdb.Set(ctx, "shellpath", "/usr/syscmds/", 0)
+
+	const maxRetries = 1000
+
+	// Retry if the key has been changed.
+	for i := 0; i < maxRetries; i++ {
+		err := rdb.Watch(ctx,
+			func(tx *redis.Tx) error {
+				currentPath, err := rdb.Get(ctx, "shellpath").Result()
+				newPath := currentPath + ":/usr/mycmds/"
+
+				_, err = tx.TxPipelined(ctx, func(pipe redis.Pipeliner) error {
+					pipe.Set(ctx, "shellpath", newPath, 0)
+					return nil
+				})
+
+				return err
+			},
+			"shellpath",
+		)
+
+		if err == nil {
+			// Success.
+			break
+		} else if err == redis.TxFailedErr {
+			// Optimistic lock lost. Retry the transaction.
+			continue
+		} else {
+			// Panic for any other error.
+			panic(err)
+		}
+	}
+
+	fmt.Println(rdb.Get(ctx, "shellpath").Val())
+	// >>> /usr/syscmds/:/usr/mycmds/
+	// STEP_END
+
+	// Output:
+	// OK;OK;OK;OK;OK;
+	// #0
+	// #3
+	// #4
+	// #0
+	// #3
+	// #4
+	// 1
+	// 2
+	// 3
+	// 2
+	// 4
+	// 6
+	// /usr/syscmds/:/usr/mycmds/
+}