COPY

The COPY command in DiceDB is used to create a copy of a key. This command allows you to duplicate the value stored at a specified key to a new key. The new key can be in the same database or a different database. This command is useful for duplicating data without the need to retrieve and reinsert it manually.

Syntax

COPY <source> <destination> [DB destination-db] [REPLACE]

Parameters

Parameter	Description	Type	Required
source	The key of the value you want to copy. This key must exist.	String	Yes
destination	The key where the value will be copied to. This key must not exist unless the REPLACE option is specified.	String	Yes
REPLACE	If specified, the command will overwrite the destination key if it already exists.	String	Optional

Return Value

Condition	Return Value
key was copied successfully	1
key was not copied	0

Behaviour

When the COPY command is executed, DiceDB will:

1. Check if the source key exists. If it does not, the command will return 0.
2. Check if the destination key exists. If it does and the REPLACE option is not specified, the command will return 0.
3. If the DB destination-db option is specified, DiceDB will switch to the specified database for the destination key.
4. Copy the value from the source key to the destination key.
5. Return 1 if the copy operation was successful.

Errors

The COPY command can raise the following errors:

1. Wrong type of value or key:
   • Error message (error) WRONGTYPE Operation against a key holding the wrong kind of value:
   • This error occurs if the source key holds a value that is not compatible with the COPY operation.
2. Not existent key:
   • Error message: (error) ERR no such key
   • This error occurs if the source key does not exist.
   • This error occurs if the destination key already exists and the REPLACE option is not specified.

Example Usage

Basic Copy

Copy the value from key1 to key2 in the same database.

127.0.0.1:7379> COPY key1 key2
(integer) 1

Copy with REPLACE

Copy the value from key1 to key2, replacing key2 if it already exists.

127.0.0.1:7379> COPY key1 key2 REPLACE
(integer) 1

Not-Existent Source Key

127.0.0.1:7379> COPY nonexistent key2
(integer) 0

Destination key already exist

127.0.0.1:7379> COPY key1 key2
(integer) 1
127.0.0.1:7379> COPY key1 key2
(integer) 0

Notes

• The COPY command is available starting from DiceDB version 6.2.
• The COPY command is atomic, meaning that the copy operation is performed as a single, indivisible operation.
• The COPY command does not modify the source key; it only duplicates its value to the destination key.
• The DB destinationDB is not yet supported with the current versions of DiceDB. It acts as a placeholder for now. It will still return 0 By understanding the COPY command and its parameters, you can effectively duplicate keys within your DiceDB databases, ensuring data consistency and reducing the need for manual data manipulation.