cmd_zcount.go

cmd_zcount.go - Overview

This file implements the ZCOUNT command, which counts the number of members in a sorted set within a specified range.

Detailed Documentation

cZCOUNT

var cZCOUNT = &CommandMeta{
	Name:      "ZCOUNT",
	Syntax:    "ZCOUNT key min max",
	HelpShort: "Counts the number of members in a sorted set between min and max (inclusive)",
	HelpLong: `
		Counts the number of members in a sorted set between min and max (inclusive)
		Use -inf and +inf for unbounded ranges
		Returns the count of members in a sorted set between min and max
		Returns 0 if the key does not exist
	`,
	Examples: `
		localhost:7379> ZCOUNT myzset 11 15
		OK 0

		localhost:7379> ZCOUNT myzset 5 10
		OK 3

		localhost:7379> ZCOUNT myzset 11
		ERR wrong number of arguments for 'ZCOUNT' command
	`,
	Eval:    evalZCOUNT,
	Execute: executeZCOUNT,
}

• Purpose: Defines the metadata for the ZCOUNT command, including its name, syntax, help messages, examples, and the functions to evaluate and execute the command.
• Properties:
  • Name: The name of the command ("ZCOUNT").
  • Syntax: The command's syntax ("ZCOUNT key min max").
  • HelpShort: A short description of the command.
  • HelpLong: A detailed description of the command, including usage with -inf and +inf.
  • Examples: Examples of how to use the command.
  • Eval: The evalZCOUNT function, which evaluates the command.
  • Execute: The executeZCOUNT function, which executes the command.

init

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

• Purpose: Registers the ZCOUNT command with the CommandRegistry.

evalZCOUNT

func evalZCOUNT(c *Cmd, s *dstore.Store) (*CmdRes, error) {
	// check number of arguments
	if len(c.C.Args) != 3 {
		return cmdResNil, errors.ErrWrongArgumentCount("ZCOUNT")
	}

	key := c.C.Args[0]
	minArg := c.C.Args[1]
	maxArg := c.C.Args[2]

	// parse minVal and maxVal scores
	minVal, errMin := strconv.ParseFloat(minArg, 64)
	maxVal, errMax := strconv.ParseFloat(maxArg, 64)
	if errMin != nil || errMax != nil {
		return cmdResNil, errors.ErrInvalidNumberFormat
	}

	// retrieve object from store
	obj := s.Get(key)
	if obj == nil {
		return cmdResInt0, nil
	}

	// ensure object is a valid sorted set
	var sortedSet *sortedset.Set
	sortedSet, err := sortedset.FromObject(obj)
	if err != nil {
		return cmdResNil, errors.ErrWrongTypeOperation
	}

	// get count of members within range from sorted set
	count := sortedSet.CountInRange(minVal, maxVal)

	return &CmdRes{R: &wire.Response{
		Value: &wire.Response_VInt{VInt: int64(count)},
	}}, nil
}

• Purpose: Evaluates the ZCOUNT command, retrieves the sorted set from the store, and counts the number of members within the specified range.
• Parameters:
  • c: A pointer to the Cmd struct, which contains the command arguments.
  • s: A pointer to the dstore.Store struct, which represents the data store.
• Returns:
  • A pointer to a CmdRes struct, which contains the result of the command.
  • An error, if any occurred.

executeZCOUNT

func executeZCOUNT(c *Cmd, sm *shardmanager.ShardManager) (*CmdRes, error) {
	if len(c.C.Args) != 3 {
		return cmdResNil, errors.ErrWrongArgumentCount("ZCOUNT")
	}

	shard := sm.GetShardForKey(c.C.Args[0])
	return evalZCOUNT(c, shard.Thread.Store())
}

• Purpose: Executes the ZCOUNT command by retrieving the appropriate shard and calling evalZCOUNT on that shard's store.
• Parameters:
  • c: A pointer to the Cmd struct, which contains the command arguments.
  • sm: A pointer to the shardmanager.ShardManager struct, which manages the shards.
• Returns:
  • A pointer to a CmdRes struct, which contains the result of the command.
  • An error, if any occurred.

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