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DiceDB

BF.ADD

A Bloom Filter is a probabilistic data structure that is used to test whether an element is a member of a set. It is highly space-efficient but allows for a small probability of false positives. The BF.ADD command is used to add an element to a Bloom Filter.

Syntax

Terminal window
BF.ADD key item

Parameters

ParameterDescriptionTypeRequired
keyThe name of the Bloom Filter to which the item will be added.StringYes
itemThe item to be added to the Bloom Filter.StringYes

Return values

ConditionReturn Value
Item was not already present in the Bloom Filter1
Item was already present in the Bloom Filter (could be wrong)0

Behaviour

When the BF.ADD command is executed, the specified item is added to the Bloom Filter associated with the given key. If the Bloom Filter does not already exist, it will be created automatically. The command will then check if the item is already present in the Bloom Filter:

  • If the item is not present, it will be added, and the command will return 1.
  • If the item is already present, the command will return 0.

Errors

  1. Incorrect number of arguments:
    • Error message: (error) ERR wrong number of arguments for 'BF.ADD' command
    • The command requires exactly two arguments: the key and the item to be added to the Bloom Filter.
  2. Key is not a Bloom Filter:
    • Error message: (error) WRONGTYPE Operation against a key holding the wrong kind of value
    • The specified key does not refer to a Bloom Filter.

Example Usage

Adding an Item to a Bloom Filter

Terminal window
127.0.0.1:7379> BF.ADD mybloomfilter "apple"
(integer) 1

In this example, the item “apple” is added to the Bloom Filter named mybloomfilter. Since “apple” was not already present, the command returns 1.

Adding an Existing Item to a Bloom Filter

Terminal window
127.0.0.1:7379> BF.ADD mybloomfilter "apple"
(integer) 0

In this example, the item “apple” is added to the Bloom Filter named mybloomfilter again. Since “apple” was already present, the command returns 0.

Error Scenario: Wrong Number of Arguments

Terminal window
127.0.0.1:7379> BF.ADD mybloomfilter
(error) ERR wrong number of arguments for 'bf.add' command

In this example, the command is called with only one argument instead of the required two. An error is raised indicating the wrong number of arguments.

Error Scenario: Non-string Key or Item

Terminal window
127.0.0.1:7379> SET k 67890
OK
127.0.0.1:7379> BFADD 12345 67890
(error) WRONGTYPE Operation against a key holding the wrong kind of value

In this example, the key and item are non-string values. An error is raised indicating the wrong type of value.