Hashes

Hash Commands

Hashes are maps of field-value pairs, ideal for representing objects. Each hash can store over 4 billion field-value pairs.

HSET

Synopsis: HSET key field value [field value ...]

Set one or more field-value pairs in a hash. Creates the hash if it does not exist. Returns the number of new fields added (fields that were updated are not counted).

> HSET user:1 name "Alice" age "30" email "alice@example.com"
(integer) 3
> HSET user:1 age "31"
(integer) 0

HGET

Synopsis: HGET key field

Return the value associated with a field in a hash. Returns nil if the field or hash does not exist.

> HSET user:1 name "Alice"
OK
> HGET user:1 name
"Alice"
> HGET user:1 nonexistent
(nil)

HMSET

Synopsis: HMSET key field value [field value ...]

Set multiple field-value pairs in a hash. Deprecated in favor of HSET which now accepts multiple pairs.

> HMSET user:1 name "Alice" age "30"
OK

HMGET

Synopsis: HMGET key field [field ...]

Return the values associated with the specified fields in a hash. Returns nil for fields that do not exist.

> HSET user:1 name "Alice" age "30"
(integer) 2
> HMGET user:1 name age nonexistent
1) "Alice"
2) "30"
3) (nil)

HGETALL

Synopsis: HGETALL key

Return all fields and values in a hash. The result is a flat list of alternating field-name and field-value entries.

> HSET user:1 name "Alice" age "30"
(integer) 2
> HGETALL user:1
1) "name"
2) "Alice"
3) "age"
4) "30"

HDEL

Synopsis: HDEL key field [field ...]

Remove one or more fields from a hash. Returns the number of fields that were removed.

> HSET user:1 name "Alice" age "30"
(integer) 2
> HDEL user:1 age
(integer) 1
> HDEL user:1 nonexistent
(integer) 0

HEXISTS

Synopsis: HEXISTS key field

Determine whether a field exists in a hash. Returns 1 if the field exists, 0 otherwise.

> HSET user:1 name "Alice"
(integer) 1
> HEXISTS user:1 name
(integer) 1
> HEXISTS user:1 nonexistent
(integer) 0

HLEN

Synopsis: HLEN key

Return the number of fields in a hash.

> HSET user:1 name "Alice" age "30"
(integer) 2
> HLEN user:1
(integer) 2

HKEYS

Synopsis: HKEYS key

Return all field names in a hash.

> HSET user:1 name "Alice" age "30"
(integer) 2
> HKEYS user:1
1) "name"
2) "age"

HVALS

Synopsis: HVALS key

Return all values in a hash.

> HSET user:1 name "Alice" age "30"
(integer) 2
> HVALS user:1
1) "Alice"
2) "30"

HINCRBY

Synopsis: HINCRBY key field increment

Increment the integer value of a hash field by the given amount. If the field does not exist, it is set to 0 before the operation. Returns the new value.

> HSET user:1 age "30"
(integer) 1
> HINCRBY user:1 age 5
(integer) 35

HINCRBYFLOAT

Synopsis: HINCRBYFLOAT key field increment

Increment the float value of a hash field by the given amount. Returns the new value as a bulk string.

> HSET product:1 price "19.99"
(integer) 1
> HINCRBYFLOAT product:1 price 5.01
"25"

HSETNX

Synopsis: HSETNX key field value

Set a field in a hash only if the field does not already exist. Returns 1 if the field was set, 0 if it already existed.

> HSETNX user:1 name "Alice"
(integer) 1
> HSETNX user:1 name "Bob"
(integer) 0
> HGET user:1 name
"Alice"

HRANDFIELD

Synopsis: HRANDFIELD key [count [WITHVALUES]]

Return one or more random fields from a hash.

• Without count: returns a single random field name.
• With positive count: returns up to count distinct fields.
• With negative count: returns |count| fields, possibly with duplicates.
• With WITHVALUES: includes the corresponding values.

> HSET myhash a "1" b "2" c "3"
(integer) 3
> HRANDFIELD myhash
"b"
> HRANDFIELD myhash 2 WITHVALUES
1) "a"
2) "1"
3) "c"
4) "3"

HSCAN

Synopsis: HSCAN key cursor [MATCH pattern] [COUNT count]

Incrementally iterate over fields and values in a hash. Returns a cursor and a list of field-value pairs.

> HSET myhash a "1" b "2" c "3"
(integer) 3
> HSCAN myhash 0 MATCH "*" COUNT 10
1) "0"
2) 1) "a"
   2) "1"
   3) "b"
   4) "2"
   5) "c"
   6) "3"