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Generic API

Connection Commands​

AUTH​

Syntax​

    AUTH <placeholderforpassword>

Authenticates the connection.

Resp Reply​

Simple string reply: OK, or an error if the password, or username/password pair, is invalid.

Security notice:

Only use strong and long passwords so an attack is infeasible. A better way to manage authentication will be using the ACL feature.

ECHO​

Syntax​

    ECHO <message>

Returns message.

Resp Reply​

Bulk string reply: the given string.

PING​

Syntax​

    PING key

Returns PONG if no argument is provided, otherwise return a copy of the argument as a bulk string.

Resp Reply​

Any of the following:

  • Simple string reply: PONG when no argument is provided.
  • Bulk string reply: the provided argument.

QUIT​

Syntax​

    QUIT

Ask the server to close the connection. The connection is close when all pending replies have been written to the client.

Resp Reply​

Simple string reply: OK.

Generic Commands​

DEL​

Syntax​

    DEL key [key ...]

Removes the specified keys. A key is ignored if it does not exist.

Resp Reply​

Integer reply: the number of keys that were removed.

EXISTS​

Syntax​

    EXISTS key [key ...]

Determines whether one or more keys exist. If the same existing key is mentioned in the arguments multiple times, it will be counted multiple times. So if foo exists, EXISTS foo foo will return 2.

Resp Reply​

Integer reply: the number of keys that exist from those specified as arguments.

EXPIRE​

Syntax​

    EXPIRE key seconds [NX | XX | GT | LT]

Set a timeout on key in seconds. After the timeout has expired, the key will automatically be deleted.

The EXPIRE command supports a set of options:

  • NX -- Set expiry only when the key has no expiry
  • XX -- Set expiry only when the key has an existing expiry
  • GT -- Set expiry only when the new expiry is greater than current one
  • LT -- Set expiry only when the new expiry is less than current one

Resp Reply​

One of the following:

  • Integer reply: 0 if the timeout was not set; for example, the key doesn't exist, or the operation was skipped because of the provided arguments.

  • Integer reply: 1 if the timeout was set.

KEYS​

Syntax​

    KEYS pattern

Returns all keys matching pattern.

Warning: consider KEYS as a command that should only be used in production environments with extreme care. It may ruin performance when it is executed against large databases.

Examples of supported patterns:

  • h?llo matches hello, hallo and hxllo
  • h*llo matches hllo and heeeello
  • h[ae]llo matches hello and hallo, but not hillo
  • h[^e]llo matches hallo, hbllo, ... but not hello
  • h[a-b]llo matches hallo and hbllo

Use \ to escape special characters if you want to match them verbatim.

Resp Reply​

Array reply: a list of keys matching pattern.

MIGRATE​

TODO: Verify syntax and functionality

Resp Reply​

PERSIST​

Syntax​

    PERSIST key

Removes the existing timeout on a key, turning the key from volatile (a key with an expire set) to persistent (a key that will never expire as no timeout is associated).

Resp Reply​

PEXPIRE​

Syntax​

    PEXPIRE key milliseconds [NX | XX | GT | LT]

This command works exactly like EXPIRE but the time to live of the key is specified in milliseconds instead of seconds.

Resp Reply​

One of the following:

  • Integer reply: 0 if key does not exist or does not have an associated timeout.
  • Integer reply: 1 if the timeout has been removed.

PTTL​

Syntax​

    PTTL  key

Like TTL this command returns the remaining time to live of a key that has an expire set, with the sole difference that TTL returns the amount of remaining time in seconds while PTTL returns it in milliseconds.

Resp Reply​

One of the following:

  • Integer reply: TTL in milliseconds.
  • Integer reply: -1 if the key exists but has no associated expiration.
  • Integer reply: -2 if the key does not exist.

RENAME​

Syntax​

    RENAME key newkey

Renames key to newkey. It returns an error when key does not exist. If newkey already exists it is overwritten, when this happens RENAME executes an implicit DEL operation.

Resp Reply​

Simple string reply: OK.

SCAN​

Syntax​

    SCAN cursor [MATCH pattern] [COUNT count] [TYPE type]

Iterates over the keys that exist in the store and returns only the ones matching the selected filters.

The MATCH option It is possible to only iterate elements matching a given glob-style pattern, similarly to the behavior of the KEYS command that takes a pattern as its only argument.

The TYPE option You can use the TYPE option to ask SCAN to only return objects that match a given type, allowing you to iterate through the database looking for keys of a specific type.

The COUNT option

The default COUNT value is 10, but the user is free to change it.

Resp Reply​

Array reply: specifically, an array with two elements.

  • The first element is a Bulk string reply that represents an unsigned 64-bit number, the cursor.
  • The second element is an Array reply with the names of scanned keys.

TTL​

Syntax​

    TTL key

Returns the remaining time to live of a key that has a timeout.

Resp Reply​

One of the following:

  • Integer reply: TTL in seconds.
  • Integer reply: -1 if the key exists but has no associated expiration.
  • Integer reply: -2 if the key does not exist.

TYPE​

Syntax​

    TYPE key

Returns the string representation of the type of the value stored at key. The different types that can be returned are: string, list, set, zset, and hash.

Resp Reply​

Simple string reply: the type of key, or none when key doesn't exist.

Syntax​

This command is very similar to DEL: it removes the specified keys. Just like DEL a key is ignored if it does not exist. However the command performs the actual memory reclaiming in a different thread, so it is not blocking, while DEL is.

Resp Reply​

Integer reply: the number of keys that were unlinked.