cmd_exists.go

cmd_exists.go - Overview

This file defines the EXISTS command, which returns the number of keys that exist among the provided arguments.

Detailed Documentation

cEXISTS

var cEXISTS = &CommandMeta{
	Name:      "EXISTS",
	Syntax:    "EXISTS key [key ...]",
	HelpShort: "EXISTS returns the count of keys that exist among the given",
	HelpLong:  `EXISTS command returns the count of keys that exist among the given arguments without modifying them.`,
	Examples: `
localhost:7379> SET k1 v1
OK
localhost:7379> SET k2 v2
OK
localhost:7379> EXISTS k1 k2 k3
OK 2
	`,
	Eval:    evalEXISTS,
	Execute: executeEXISTS,
}

• Purpose: Defines the metadata for the EXISTS command, including its name, syntax, help text, examples, and the functions to evaluate and execute the command.
• Properties:
  • Name: The name of the command ("EXISTS").
  • Syntax: The command's syntax ("EXISTS key [key ...]").
  • HelpShort: A short description of the command.
  • HelpLong: A longer description of the command.
  • Examples: Example usage of the command.
  • Eval: The function to evaluate the command (evalEXISTS).
  • Execute: The function to execute the command (executeEXISTS).

init

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

• Purpose: Registers the EXISTS command with the CommandRegistry.

evalEXISTS

func evalEXISTS(c *Cmd, s *dstore.Store) (*CmdRes, error) {
	if len(c.C.Args) < 1 {
		return cmdResNil, errors.ErrWrongArgumentCount("EXISTS")
	}

	var count int64
	for _, key := range c.C.Args {
		// GetNoTouch is used to check if a key exists in the store
		// without updating its last access time.
		if s.GetNoTouch(key) != nil {
			count++
		}
	}

	// Return the count as a response
	return cmdResInt(count), nil
}

• Purpose: Evaluates the EXISTS command against a single store.
• 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 representing the command result.
  • error: An error if one occurred, otherwise nil.

executeEXISTS

func executeEXISTS(c *Cmd, sm *shardmanager.ShardManager) (*CmdRes, error) {
	if len(c.C.Args) < 1 {
		return cmdResNil, errors.ErrWrongArgumentCount("EXISTS")
	}
	var count int64
	var shardMap = make(map[*shard.Shard][]string)
	for _, key := range c.C.Args {
		shard := sm.GetShardForKey(key)
		shardMap[shard] = append(shardMap[shard], key)
	}

	for shard, keys := range shardMap {
		c.C.Args = keys
		r, err := evalEXISTS(c, shard.Thread.Store())
		if err != nil {
			return nil, err
		}
		count += r.R.GetVInt()
	}
	return cmdResInt(count), nil
}

• Purpose: Executes the EXISTS command across multiple shards.
• Parameters:
  • c: A pointer to the Cmd struct representing the command.
  • sm: A pointer to the shardmanager.ShardManager struct representing the shard manager.
• Returns:
  • *CmdRes: A pointer to the CmdRes struct representing the command result.
  • error: An error if one occurred, otherwise nil.

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