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COMMANDS.md

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List of commands

Most COMMANDS take the exact same arguments, and return the same type of value, as their respective Redis™ commands.

Command Description
APPEND key value Append a value to a key
BGSAVE Asynchronously save the dataset to disk
CLIENT ID Returns the client ID for the current connection
CLIENT KILL ID id [id ..] Kill the connection of a client
CLIENT LIST Get the list of client connections
CONVERT Convert a plaintext database to binary or vice-versa
DEL key [key ..] Delete one or more keys
EXISTS key [key ..] Determine if a key exists
GET key Get the value of a key
GETSET key value Set the string value of a key and return its old value
HDEL key field [field ..] Delete one or more hash fields
HEXISTS key field Determine if a hash field exists
HFIND key substring Find a substring in a hash key's field
HGET key field Get the value of a hash field
HGETALL key Get all the fields and values in a hash
HKEYS key Get all the fields in a hash
HLEN key Get the number of fields in a hash
HMGET key field [field ..] Get the values of all the given hash fields
HSET key field value [field value ..] Set the string value of a hash field
HSTRLEN key field Get the length of the value of a hash field
HVALS key Get all the values in a hash
INFO [section] Get information and statistics about the server
LINDEX key index Get an element from a list by its index
LLEN key Get the length of a list
LPOP key Remove and get the first element in a list
LPOPRPUSH source destination Remove the first element in a list, append it to another list and return it
LPUSH key element [element ..] Prepend one or multiple elements to a list
LRANGE key start stop Get a range of elements from a list
LREM key count element Remove elements from a list
LSET key index element Set the value of an element in a list by its index
LTRIM key start stop Trim a list to the specified range
MGET key [key ..] Get the values of all the given keys
MSET key value [key value ..] Set multiple keys to multiple values
PING [message] Ping the server
RPOP key Remove and get the last element in a list
RPOLRPUSH source destination Remove the last element in a list, prepend it to another list and return it
RPUSH key element [element ..] Append one or multiple elements to a list
SAVE Synchronously save the dataset to disk
SET key value Set the string value of a key
STRLEN key Get the length of the value stored in a key

APPEND

APPEND key value

If key already exists and is a string, this command appends the value at the end of the string.

Return values

  • Integer: the length of the string after the append operation
  • NIL: if key is not a string or does not exist

CLI example

./client.l --pass yourpass EXISTS mykey
0
./client.l --pass yourpass SET mykey "Hello"
OK
./client.l --pass yourpass APPEND mykey " World"
11
./client.l --pass yourpass GET mykey
Hello World

PicoLisp example

: (kv-send-data '("EXISTS" "mykey"))
-> 0
: (kv-send-data '("SET" "mykey" "Hello"))
-> "OK"
: (kv-send-data '("APPEND" "mykey" " World"))
-> 11
: (kv-send-data '("GET" "mykey"))
-> "Hello World"
: (kv-send-data '("APPEND" "doesntexist" "test"))
-> NIL

BGSAVE

BGSAVE

Save the DB in background.

The KV server forks, the parent continues to serve the clients, the child saves the DB on disk then exits.

An error is returned if there is already a background save running or if there is another non-background-save process running.

Return values

  • String: Background saving started if the BGSAVE started correctly or Error: DB is locked for writing if the DB is locked.

CLI example

./client.l --pass yourpass BGSAVE
Background saving started

PicoLisp example

: (kv-send-data '("BGSAVE"))
-> "Background saving started"

CLIENT ID

CLIENT ID

The command just returns the ID of the current connection. Every connection ID has certain guarantees:

  1. It is never repeated, so if CLIENT ID returns the same number, the caller can be sure that the underlying client did not disconnect and reconnect the connection, but it is still the same connection.
  2. The ID is monotonically incremental. If the ID of a connection is greater than the ID of another connection, it is guaranteed that the second connection was established with the server at a later time.

Return values

  • Integer: The id of the client.

CLI example

./client.l --pass yourpass CLIENT ID
1
./client.l --pass yourpass CLIENT ID
2

PicoLisp example

: (kv-send-data '("CLIENT" "ID"))
-> 3

CLIENT KILL ID

CLIENT ID id [id ..]

The command allows to end one or more client connections by their unique ID field.

Return values

  • String: the number of clients connections ended.

CLI example

./client.l --pass yourpass CLIENT KILL ID 2
1

PicoLisp example

: (kv-send-data '("CLIENT" "KILL" "ID" "2"))
-> 0

CLIENT LIST

CLIENT LIST

Returns information and statistics about the client connections server in a mostly human readable format.

The KV server forks, the parent continues to serve the clients, the child saves the DB on disk then exits.

An error is returned if there is already a background save running or if there is another non-background-save process running.

Return values

  • Multi-line String: a unique string, formatted as follows:
    • One client connection per line (separated by \n newline/linefeed)
    • Each line is composed of a succession of property=value fields separated by a space character.

Here is the meaning of the fields:

  • id: a unique auto-incrementing 64-bit client ID
  • pid: process ID of the forked child handling the request
  • name: name set by the client, with --name or autogenerated
  • addr: address of the client
  • port: source port of the client
  • fd: file descriptor corresponding to the socket

CLI example

./client.l --pass yourpass CLIENT LIST
id=1 pid=16929 name=4AF35825 addr=::1 port=49774 fd=7

PicoLisp example

: (kv-send-data '("CLIENT" "LIST"))
-> "id=2 pid=10019 name=79738D13 addr=::1 port=50956 fd=7"

CONVERT

CONVERT

Convert a plaintext database to binary or vice-versa.

The KV server by default saves data on disk in plaintext format, which can be modified by hand by anyone with practically no PicoLisp knowledge. The disadvantage with plaintext is its on-disk footprint is quite large compared to binary. For small datasets the difference is negligible, but it could also affect performance when first loading the database.

While the server is running, it is possible to dump the database to disk using a different format, for example: if it's currently saving in plaintext, CONVERT will dump it to disk in binary. All future saves will also be in binary until the server is restarted, or until another CONVERT command is sent (which would convert it back to plaintext).

Using the CLI tool:

  • The default filename for binary format is kv.bin.
  • The default filename for plaintext format is kv.db.

Using the PicoLisp server library libkv.l:

The database filename can be changed through the *KV_db variable, example (setq *KV_db "/path/to/db.bin")

  • To enable binary saving in PicoLisp, use (on *KV_binary)
  • To disable binary saving in PicoLisp, use (off *KV_binary)

Return values

  • String: OK if the database was converted successfully.

CLI example

./client.l --pass yourpass CONVERT
OK

PicoLisp example

: (kv-send-data '("CONVERT"))
-> "OK"

DEL

DEL key [key ..]

Removes the specified keys. All given keys are removed whether they exist or not.

Return values

  • Integer: The number of keys that were removed.

CLI example

./client.l --pass yourpass SET key1 "Hello"
OK
./client.l --pass yourpass SET key2 "World"
OK
./client.l --pass yourpass DEL key1 key2 key3
3

PicoLisp example

: (kv-send-data '("SET" "key1" "Hello"))
-> "OK"
: (kv-send-data '("SET" "key2" "World"))
-> "OK"
: (kv-send-data '("DEL" "key1" "key2" "key3"))
-> 3

License

This documentation copies in part the Redis documentation, distributed under the Creative Commons Attribution-ShareAlike 4.0 International license license, and is modified to match the PicoLisp KV library code.

This documentation is licensed under Creative Commons Attribution-ShareAlike 4.0 International (CC BY-SA 4.0).

Copyright (c) 2020 Alexander Williams, On-Prem license@on-premises.com