RENAME and RENAMENX in Redis

Introduction

These commands change the name of a key in the database. It helps you organize or update your data by giving keys new names.

You want to change a key's name to something more meaningful.

You need to avoid overwriting an existing key when renaming.

You want to move data from one key to another without losing it.

You want to rename a key only if the new name does not exist yet.

Syntax

Redis

RENAME oldkey newkey
RENAMENX oldkey newkey

RENAME changes the key name and overwrites the new key if it exists.

RENAMENX changes the key name only if the new key does not exist; otherwise, it does nothing.

Examples

This renames the key user:1 to user:100. If user:100 exists, it will be overwritten.

Redis

RENAME user:1 user:100

This renames user:1 to user:100 only if user:100 does not exist. If it exists, the command does nothing.

Redis

RENAMENX user:1 user:100

Sample Program

This example shows how RENAME overwrites the key user:100 with user:1's value. Then it resets user:1 and tries RENAMENX, which does not rename because user:100 exists.

Redis

SET user:1 "Alice"
SET user:100 "Bob"
RENAME user:1 user:100
GET user:100
SET user:1 "Alice"
RENAMENX user:1 user:100
GET user:100
GET user:1

Important Notes

If the old key does not exist, both commands return an error.

RENAME can overwrite existing keys, so use it carefully.

RENAMENX returns 1 if the rename was successful, 0 if not.

Summary

RENAME changes a key's name and overwrites if needed.

RENAMENX changes a key's name only if the new name is free.

Use these commands to organize or update your Redis keys safely.

Practice

1. What does the Redis command RENAME do?

easy

A. Changes the name of a key and overwrites the new key if it exists

B. Changes the name of a key only if the new key does not exist

C. Deletes a key without renaming

D. Creates a copy of a key with a new name

Solution

1. Step 1: Understand the purpose of RENAME

   The RENAME command changes the name of an existing key to a new name.

2. Step 2: Check behavior when new key exists

   If the new key already exists, RENAME overwrites it without error.

3. Final Answer:

   Changes the name of a key and overwrites the new key if it exists -> Option A

4. Quick Check:

   RENAME overwrites existing keys = B [OK]

Hint: RENAME always renames and overwrites existing keys [OK]

Common Mistakes:

• Thinking RENAME only renames if new key is free
• Confusing RENAME with RENAMENX
• Assuming RENAME copies instead of renaming

2. Which of the following is the correct syntax to rename a key oldkey to newkey using RENAMENX?

easy

A. RENAMENX newkey oldkey

B. RENAME oldkey newkey

C. RENAMENX oldkey newkey

D. RENAMEX oldkey newkey

Solution

1. Step 1: Recall RENAMENX syntax

   The correct syntax is RENAMENX oldkey newkey, where the first argument is the current key and the second is the new key.

2. Step 2: Identify incorrect options

   A reverses arguments, B uses RENAME not RENAMENX, D has a typo in command name.

3. Final Answer:

   RENAMENX oldkey newkey -> Option C

4. Quick Check:

   RENAMENX oldkey newkey syntax = C [OK]

Hint: Remember: RENAMENX oldkey newkey [OK]

Common Mistakes:

• Swapping oldkey and newkey arguments
• Using RENAME instead of RENAMENX
• Typo in command name

3. Given the following Redis commands executed in order:

SET key1 "value1"
SET key2 "value2"
RENAMENX key1 key2
GET key1
GET key2

What will be the output of the two GET commands?

medium

A. GET key1: "value1", GET key2: "value2"

B. GET key1: nil, GET key2: "value1"

C. GET key1: "value1", GET key2: "value1"

D. GET key1: nil, GET key2: "value2"

Solution

1. Step 1: Analyze RENAMENX behavior

   RENAMENX renames key1 to key2 only if key2 does not exist. Here, key2 exists, so RENAMENX does nothing.

2. Step 2: Check GET results

   Since RENAMENX failed, key1 still holds "value1" and key2 holds "value2".

3. Final Answer:

   GET key1: "value1", GET key2: "value2" -> Option A

4. Quick Check:

   RENAMENX fails if new key exists = A [OK]

Hint: RENAMENX fails if new key exists, keys unchanged [OK]

Common Mistakes:

• Assuming RENAMENX overwrites existing keys
• Expecting key1 to be deleted after RENAMENX
• Confusing RENAMENX with RENAME

4. You run the command RENAMENX keyA keyB but get an error saying ERR no such key. What is the most likely cause?

medium

A. keyB does not exist

B. RENAMENX command is misspelled

C. keyB already exists

D. keyA does not exist

Solution

1. Step 1: Understand error meaning

   The error ERR no such key means the source key to rename does not exist.

2. Step 2: Identify which key is source

   In RENAMENX keyA keyB, keyA is the source key. If it does not exist, the error occurs.

3. Final Answer:

   keyA does not exist -> Option D

4. Quick Check:

   ERR no such key means source key missing = D [OK]

Hint: ERR no such key means source key missing [OK]

Common Mistakes:

• Thinking error means destination key missing
• Assuming RENAMENX overwrites keys
• Ignoring command spelling

5. You want to rename a key session123 to user_session only if user_session does not exist, and get a confirmation if rename succeeded. Which Redis command and response should you use?

hard

A. Use RENAME session123 user_session and expect OK response

B. Use RENAMENX session123 user_session and expect 1 if renamed, 0 if not

C. Use RENAMENX user_session session123 and expect 1 if renamed

D. Use RENAME user_session session123 and expect OK response

Solution

1. Step 1: Choose command that renames only if new key is free

   RENAMENX renames only if the new key does not exist, perfect for this case.

2. Step 2: Understand RENAMENX response

   RENAMENX returns 1 if rename succeeded, 0 if new key exists and rename skipped.

3. Final Answer:

   Use RENAMENX session123 user_session and expect 1 if renamed, 0 if not -> Option B

4. Quick Check:

   RENAMENX returns 1 or 0 for success/failure = A [OK]

Hint: RENAMENX returns 1 if renamed, 0 if new key exists [OK]

Common Mistakes:

• Using RENAME which always overwrites
• Swapping source and destination keys
• Expecting OK response from RENAMENX