cmd_decr.go

cmd_decr.go - Overview

This file defines the DECR command, which decrements the integer value of a specified key in the DiceDB store by 1.

Detailed Documentation

cDECR

var cDECR = &CommandMeta{
	Name:      "DECR",
	Syntax:    "DECR key",
	HelpShort: "DECR decrements the value of the specified key in args by 1",
	HelpLong: `
DECR command decrements the integer at 'key' by one. Creates 'key' as -1 if absent.
Errors on wrong type or non-integer string. Limited to 64-bit signed integers.

Returns the new value of 'key' on success.
	`,
	Examples: `
localhost:7379> SET k 43
OK OK
localhost:7379> DECR k
OK 42
	`,
	Eval:    evalDECR,
	Execute: executeDECR,
}

• Purpose: Defines the metadata for the DECR command, including its name, syntax, help text, example usage, and associated functions for evaluation and execution.
• Fields:
  • Name: The name of the command ("DECR").
  • Syntax: The syntax of the command ("DECR 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 (evalDECR).
  • Execute: The function to execute the command (executeDECR).

init

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

• Purpose: Registers the DECR command with the CommandRegistry. This function is automatically called when the package is initialized.

evalDECR

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

	return doIncr(c, s, -1)
}

• Purpose: Evaluates the DECR command. It retrieves the key from the arguments, decrements the integer value by 1, and returns the new value.
• Parameters:
  • c (*Cmd): The command context containing the arguments.
  • s (*dstore.Store): The data store instance.
• Returns:
  • *CmdRes: Response containing the new integer value after decrement.
  • error: Error if the wrong number of arguments is provided or if the value is of the wrong type.

executeDECR

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

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

• Purpose: Executes the DECR command. It determines the shard responsible for the key, retrieves the store from that shard, and then calls evalDECR to perform the decrement operation.
• Parameters:
  • c (*Cmd): The command context containing the arguments.
  • sm (*shardmanager.ShardManager): The shard manager instance.
• Returns:
  • *CmdRes: Response containing the new integer value after decrement.
  • error: Error if the wrong number of arguments is provided or if evalDECR returns an error.

Getting Started Relevance