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DiceDB

SDIFF

The SDIFF command in DiceDB is used to compute the difference between multiple sets. It returns the members of the set resulting from the difference between the first set and all the successive sets. This command is useful when you need to find elements that are unique to the first set compared to other sets.

Syntax

Terminal window
SDIFF key1 [key2 ... keyN]

Parameters

ParameterDescriptionTypeRequired
key1The key of the first set.StringYes
key2..keyNThe keys of the subsequent sets to be compared with the first set.StringNo

Return Values

The SDIFF command returns an array of elements that are present in the first set but not in any of the subsequent sets. If the first set does not exist, it is considered an empty set. If none of the sets exist, an empty array is returned.

ConditionReturn Value
Elements present in the first set but not in any subsequent setsArray of elements
First set does not existEmpty array
None of the sets existEmpty array
Syntax or specified constraints are invaliderror

Behaviour

  • DiceDB retrieves the set associated with key1.
  • DiceDB retrieves the sets associated with key2 through keyN.
  • DiceDB computes the difference by removing elements found in key2 through keyN from the set found in key1.
  • The resulting set, containing elements unique to key1, is returned.

Errors

  • Wrong Type Error:

    • Error Message: (error) WRONGTYPE Operation against a key holding the wrong kind of value
    • If any of the keys provided do not hold a set, DiceDB will return an error of type WRONGTYPE. This error indicates that the operation against a key holding the wrong kind of value was attempted.

  • Wrong number of arguments:

    • Error Message: (error) ERR wrong number of arguments for 'sdiff' command
    • If no keys are provided, DiceDB will return a syntax error indicating that at least one key must be specified.

  • Syntax Error: If no keys are provided, DiceDB will return a syntax error indicating that at least one key must be specified.

Example Usage

Basic Usage

In this example, the difference between set1 and the union of set2 and set3 is computed. The element “b” is unique to set1.

Terminal window
127.0.0.1:7379> SADD set1 "a" "b" "c"
127.0.0.1:7379> SADD set2 "c" "d" "e"
127.0.0.1:7379> SADD set3 "a" "f"
127.0.0.1:7379> SDIFF set1 set2 set3


"b"

Single Set

In this example, since only one set is provided, the command returns all elements of set1.

Terminal window
127.0.0.1:7379> SADD set1 "a" "b" "c"
127.0.0.1:7379> SDIFF set1
1) "a"
2) "b"
3) "c"

Non-Existent Sets

In this example, since neither set1 nor set2 exist, the command returns an empty array.

Terminal window
127.0.0.1:7379> SDIFF set1 set2
(empty array)

Wrong Type Error

In this example, not_a_set is not a set, so DiceDB returns a WRONGTYPE error.

Terminal window
127.0.0.1:7379> SET not_a_set "value"
127.0.0.1:7379> SDIFF not_a_set
(error) WRONGTYPE Operation against a key holding the wrong kind of value

Syntax Error

In this example, no keys are provided, so DiceDB returns a syntax error.

Terminal window
127.0.0.1:7379> SDIFF
(error) ERR wrong number of arguments for 'sdiff' command