Add hash support

[elimisteve]

I couldn't get the Go + redigo equivalent of

HMSET myhash field1 "Hello" field2 "World"

to work ("ERR wrong number of arguments for 'hmset' command"). Native hash support would be nice to get around this and provide convenience functions.

[garyburd]

Redigo can execute any command including HMSET. Can you share the line of code where you invoke HMSET?

[elimisteve]

package main

import (
    "fmt"
    "github.com/garyburd/redigo/redis"
    "log"
)

var (
    conn redis.Conn
)

// Connect to Redis
func init() {
    var err error
    conn, err = redis.Dial("tcp", ":6379")
    if err != nil {
        log.Fatalf("Couldn't connect to Redis: %v\n", err)
    }
}

func main() {
    defer conn.Close()

    stockData := map[string]map[string]string{
        "GOOG": {"company_name":"Google Inc.", "open_price":"803.99", "ask_price":"795.50", "close_price":"802.66", "bid_price":"793.36"},
        "MSFT": {"ask_price":"N/A", "open_price":"28.30", "company_name":"Microsoft Corpora", "bid_price":"28.50", "close_price":"28.37"},
    }

    conn.Send("HMSET", "stocks")
    // conn.Send("HMSET")
    // conn.Send("stocks")
    // var cmd []interface{}
    for sym, row := range stockData {
        for colName, val := range row {
            key := sym + ":" + colName
            // cmd = append(cmd, key, val)
            conn.Send(key, val)
        }
    }
    // conn.Send("HMSET", cmd...)
    reply, err := conn.Do("EXEC")
    if err != nil {
        log.Fatalf("Error setting hash: %v\n", err)
    }
    fmt.Printf("reply == %+v\n", reply)
}

[elimisteve]

The comments reveal the other versions I've also tried, such as sending (almost) all the commands at once with conn.Send("HMSET", cmd...). conn.Send("HMSET", "stocks", cmd...) doesn't compile.

Any idea what I'm doing wrong?

[garyburd]

The following examples show how to create one hash for each symbol.

package main

import (
    "github.com/garyburd/redigo/redis"
    "log"
)

func main() {
    conn, err := redis.Dial("tcp", ":6379")
    if err != nil {
        log.Fatalf("Couldn't connect to Redis: %v\n", err)
    }
    defer conn.Close()

    stockData := map[string]map[string]string{
        "GOOG": {"company_name": "Google Inc.", "open_price": "803.99", "ask_price": "795.50", "close_price": "802.66", "bid_price": "793.36"},
        "MSFT": {"ask_price": "N/A", "open_price": "28.30", "company_name": "Microsoft Corpora", "bid_price": "28.50", "close_price": "28.37"},
    }

    // Example 1: Write command arguments out explicitly.

    for sym, row := range stockData {
        if _, err := conn.Do("HMSET", sym,
            "company_name", row["company_name"],
            "open_price", row["open_price"],
            "ask_price", row["ask_price"],
            "bid_price", row["bid_price"]); err != nil {
            log.Fatal(err)
        }
    }

    printAndDel(conn, "example 1", stockData)

    // Example 2: Construct command arguments using range over a row map.

    for sym, row := range stockData {
        args := []interface{}{sym}
        for k, v := range row {
            args = append(args, k, v)
        }
        if _, err := conn.Do("HMSET", args...); err != nil {
            log.Fatal(err)
        }
    }

    printAndDel(conn, "example 2", stockData)

    // Example 3: Construct command arguments using Redigo helper function.

    for sym, row := range stockData {
        if _, err := conn.Do("HMSET", redis.Args{sym}.AddFlat(row)...); err != nil {
            log.Fatal(err)
        }
    }

    printAndDel(conn, "example 3", stockData)
}

func printAndDel(conn redis.Conn, message string, stockData map[string]map[string]string) {
    log.Print(message)
    for sym := range stockData {
        values, err := redis.Values(conn.Do("HGETALL", sym))
        if err != nil {
            log.Fatal(err)
        }
        log.Print(sym)
        for i := 0; i < len(values); i += 2 {
            log.Printf("  %s: %s", values[i], values[i+1])
        }
    }
    for sym := range stockData {
        if _, err := conn.Do("DEL", sym); err != nil {
            log.Fatal(err)
        }
    }
}

[garyburd]

Here's another example that uses struct instead of map. This example stores the data in the same format as the previous examples.

package main

import (
    "github.com/garyburd/redigo/redis"
    "log"
)

type Stock struct {
    CompanyName string `redis:"company_name"`
    OpenPrice   string `redis:"open_price"`
    AskPrice    string `redis:"ask_price"`
    ClosePrice  string `redis:"close_price"`
    BidPrice    string `redis:"bid_price"`
}

func main() {
    conn, err := redis.Dial("tcp", ":6379")
    if err != nil {
        log.Fatalf("Couldn't connect to Redis: %v\n", err)
    }
    defer conn.Close()

    stockData := map[string]*Stock{
        "GOOG": &Stock{CompanyName: "Google Inc.", OpenPrice: "803.99", AskPrice: "795.50", ClosePrice: "802.66", BidPrice: "793.36"},
        "MSFT": &Stock{AskPrice: "N/A", OpenPrice: "28.30", CompanyName: "Microsoft Corpora", BidPrice: "28.50", ClosePrice: "28.37"},
    }

    for sym, row := range stockData {
        if _, err := conn.Do("HMSET", redis.Args{sym}.AddFlat(row)...); err != nil {
            log.Fatal(err)
        }
    }

    for sym := range stockData {
        values, err := redis.Values(conn.Do("HGETALL", sym))
        if err != nil {
            log.Fatal(err)
        }
        var stock Stock
        if err := redis.ScanStruct(values, &stock); err != nil {
            log.Fatal(err)
        }
        log.Printf("%s: %+v", sym, &stock)
    }
}

[elimisteve]

Great examples, thanks! I read some more and it sounds like Redis doesn't support nested hashes, so I suppose what I was trying to do won't work: creating one Redis hash that contains another hash from symbols to stock data. I may try the probably-good-enough hack of storing some JSON as a string since that's really what I need.

One way or the other, I'll be able to make this work, especially with the examples you've given. Thanks again!

[garyburd]

Nested hashes are not supported. The free and short The Little Redis Book gives a nice overview the types supported by Redis.

It's common to store JSON in Redis. If you are only accessing the data from Go, then encoding/gob is another good option for storing nested data.