cmd_hgetall.go

cmd_hgetall.go - Overview

This file implements the HGETALL command, which retrieves all field-value pairs from a string-string map (SSMap) stored under a given key in the database.

Detailed Documentation

cHGETALL

var cHGETALL = &CommandMeta{
	Name:      "HGETALL",
	Syntax:    "HGETALL key",
	HelpShort: "HGETALL returns all the field-value pairs for the key from the string-string map",
	HelpLong: `
HGETALL returns all the field-value pairs for the key from the string-string map.

The command returns (nil) if the key does not exist or the map is empty.
	`,
	Examples: `
localhost:7379> HSET k1 f1 v1 f2 v2 f3 v3
OK 3
localhost:7379> HGETALL k1
OK 
f1=v1
f2=v2
f3=v3
localhost:7379> HGETALL k2
OK (nil)
	`,
	Eval:    evalHGETALL,
	Execute: executeHGETALL,
}

• Purpose: Defines the metadata for the HGETALL command, including its name, syntax, help messages, examples, and the functions to evaluate and execute it.
• Properties:
  • Name: The name of the command ("HGETALL").
  • Syntax: The command's syntax ("HGETALL key").
  • HelpShort: A short description of the command.
  • HelpLong: A longer, more detailed description of the command.
  • Examples: Example usages of the command.
  • Eval: The function (evalHGETALL) responsible for evaluating the command.
  • Execute: The function (executeHGETALL) responsible for executing the command.

init

func init() {
	CommandRegistry.AddCommand(cHGETALL)
}

• Purpose: Registers the HGETALL command with the CommandRegistry during package initialization.

evalHGETALL

func evalHGETALL(c *Cmd, s *dstore.Store) (*CmdRes, error) {
	key := c.C.Args[0]
	var m SSMap

	obj := s.Get(key)
	if obj != nil {
		if err := object.AssertType(obj.Type, object.ObjTypeSSMap); err != nil {
			return cmdResNil, errors.ErrWrongTypeOperation
		}
		m = obj.Value.(SSMap)
	}

	if len(m) == 0 {
		return cmdResNil, nil
	}

	return &CmdRes{R: &wire.Response{
		VSsMap: m,
	}}, nil
}

• Purpose: Evaluates the HGETALL command. It retrieves the string-string map (SSMap) associated with the given key from the store and returns all field-value pairs.
• Parameters:
  • c: A pointer to the Cmd struct representing the command.
  • s: A pointer to the dstore.Store struct representing the data store.
• Returns:
  • *CmdRes: A pointer to the CmdRes struct, which contains the response data (a map of string-string pairs) if successful. Returns cmdResNil if the key does not exist or the map is empty.
  • error: An error object, or nil if the command was evaluated successfully. Returns errors.ErrWrongTypeOperation if the object stored at the key is not of type object.ObjTypeSSMap.

executeHGETALL

func executeHGETALL(c *Cmd, sm *shardmanager.ShardManager) (*CmdRes, error) {
	if len(c.C.Args) != 1 {
		return cmdResNil, errors.ErrWrongArgumentCount("HGETALL")
	}
	shard := sm.GetShardForKey(c.C.Args[0])
	return evalHGETALL(c, shard.Thread.Store())
}

• Purpose: Executes the HGETALL command. It retrieves the appropriate shard based on the key, then calls evalHGETALL to perform the actual retrieval of the map.
• Parameters:
  • c: A pointer to the Cmd struct representing the command.
  • sm: A pointer to the shardmanager.ShardManager struct, used to manage data shards.
• Returns:
  • *CmdRes: A pointer to the CmdRes struct, containing the response from evalHGETALL.
  • error: An error object, or nil if execution was successful. Returns errors.ErrWrongArgumentCount if the number of arguments is incorrect.

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