cmd_getdel.go

cmd_getdel.go - Overview

This file defines the GETDEL command, which retrieves the value of a key and then deletes it from the store.

Detailed Documentation

cGETDEL

var cGETDEL = &CommandMeta{
	Name:      "GETDEL",
	Syntax:    "GETDEL key",
	HelpShort: "GETDEL returns the value of the key and then deletes the key.",
	HelpLong: `
GETDEL returns the value of the key and then deletes the key.

The command returns (nil) if the key does not exist.
	`,
	Examples: `
localhost:7379> SET k v
OK OK
localhost:7379> GETDEL k
OK v
localhost:7379> GET k
(nil)
	`,
	Eval:    evalGETDEL,
	Execute: executeGETDEL,
}

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

init

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

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

evalGETDEL

func evalGETDEL(c *Cmd, s *dstore.Store) (*CmdRes, error) {
	if len(c.C.Args) != 1 {
		return cmdResNil, errors.ErrWrongArgumentCount("GETDEL")
	}

	key := c.C.Args[0]

	// Getting the key based on previous touch value
	obj := s.GetNoTouch(key)
	if obj == nil {
		return cmdResNil, nil
	}

	// Get the key from the hash table
	// TODO: Evaluate the need for having GetDel
	// implemented in the store. It might be better if we can
	// keep the business logic untangled from the store.
	objVal := s.GetDel(key)

	// Decode and return the value based on its encoding
	switch oType := objVal.Type; oType {
	case object.ObjTypeInt:
		// Value is stored as an int64, so use type assertion
		return &CmdRes{R: &wire.Response{
			Value: &wire.Response_VInt{VInt: objVal.Value.(int64)},
		}}, nil
	case object.ObjTypeString:
		// Value is stored as a string, use type assertion
		return &CmdRes{R: &wire.Response{
			Value: &wire.Response_VStr{VStr: objVal.Value.(string)},
		}}, nil
	default:
		return cmdResNil, errors.ErrWrongTypeOperation
	}
}

• Purpose: Evaluates the GETDEL command, retrieving the value associated with the given key from the store and deleting the key.
• Parameters:
  • c (*Cmd): The command context, containing the arguments.
  • s (*dstore.Store): The data store instance.
• Returns:
  • *CmdRes: A command result containing the value of the key, or cmdResNil if the key does not exist or is expired.
  • error: An error if the number of arguments is incorrect or if the value type is unexpected.

executeGETDEL

func executeGETDEL(c *Cmd, sm *shardmanager.ShardManager) (*CmdRes, error) {
	if len(c.C.Args) != 1 {
		return cmdResNil, errors.ErrWrongArgumentCount("GETDEL")
	}

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

• Purpose: Executes the GETDEL command by retrieving the appropriate shard based on the key, and then calling evalGETDEL on that shard's store.
• Parameters:
  • c (*Cmd): The command context, containing the arguments.
  • sm (*shardmanager.ShardManager): The shard manager instance.
• Returns:
  • *CmdRes: The result from evalGETDEL.
  • error: An error if the number of arguments is incorrect.

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