[redis.git] / doc / Lists.html


<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN">
<html>
    <head>
        <link type="text/css" rel="stylesheet" href="style.css" />
    </head>
    <body>
        <div id="page">
        
            <div id='header'>
            <a href="index.html">
            <img style="border:none" alt="Redis Documentation" src="redis.png">
            </a>
            </div>
        
            <div id="pagecontent">
                <div class="index">
<!-- This is a (PRE) block.  Make sure it's left aligned or your toc title will be off. -->
<b>Lists: Contents</b><br>&nbsp;&nbsp;<a href="#Redis List Type">Redis List Type</a><br>&nbsp;&nbsp;<a href="#Implementation details">Implementation details</a>
                </div>
                
                <h1 class="wikiname">Lists</h1>

                <div class="summary">
                    
                </div>

                <div class="narrow">
                    &iuml;&raquo;&iquest;#sidebar <a href="ListCommandsSidebar.html">ListCommandsSidebar</a><h1><a name="Redis List Type">Redis List Type</a></h1>Redis Lists are lists of <a href="Strings.html">Redis Strings</a>, sorted by insertion order. It's possible to add elements to a Redis List pushing new elements on the head (on the left) or on the tail (on the right) of the list.<br/><br/>The <a href="RpushCommand.html">LPUSH</a> command inserts a new elmenet on head, while <a href="RpushCommand.html">RPUSH</a> inserts a new element on tail. A new list is created when one of this operations is performed against an empty key.<br/><br/>For instance if perform the following operations:
<pre class="codeblock python" name="code">
LPUSH mylist a   # now the list is &quot;a&quot;
LPUSH mylist b   # now the list is &quot;b&quot;,&quot;a&quot;
RPUSH mylist c   # now the list is &quot;b&quot;,&quot;a&quot;,&quot;c&quot; (RPUSH was used this time)
</pre>
The resulting list stored at <i>mylist</i> will contain the elements &quot;b&quot;,&quot;a&quot;,&quot;c&quot;.<br/><br/>The max length of a list is 232-1 elements (4294967295, more than 4 billion of elements per list).<h1><a name="Implementation details">Implementation details</a></h1>Redis Lists are implemented as doubly liked lists. A few commands benefit from the fact the lists are doubly linked in order to reach the needed element starting from the nearest extreme (head or tail). <a href="LrangeCommand.html">LRANGE</a> and <a href="LindexCommand.html">LINDEX</a> are examples of such commands.<br/><br/>The use of linked lists also guarantees that regardless of the length of the list pushing and popping are O(1) operations.<br/><br/>Redis Lists cache length information so <a href="LlenCommand.html">LLEN</a> is O(1) as well.
                </div>
        
            </div>
        </div>
    </body>
</html>
Commit	Line	Data
8fb13ce8	1
	2	<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN">
	3	<html>
	4	<head>
	5	<link type="text/css" rel="stylesheet" href="style.css" />
	6	</head>
	7	<body>
	8	<div id="page">
	9
	10	<div id='header'>
	11	<a href="index.html">
	12	<img style="border:none" alt="Redis Documentation" src="redis.png">
	13	</a>
	14	</div>
	15
	16	<div id="pagecontent">
	17	<div class="index">
	18	<!-- This is a (PRE) block. Make sure it's left aligned or your toc title will be off. -->
	19	<b>Lists: Contents</b><br>  <a href="#Redis List Type">Redis List Type</a><br>  <a href="#Implementation details">Implementation details</a>
	20	</div>
	21
	22	<h1 class="wikiname">Lists</h1>
	23
	24	<div class="summary">
	25
	26	</div>
	27
	28	<div class="narrow">
	29	ï»¿#sidebar <a href="ListCommandsSidebar.html">ListCommandsSidebar</a><h1><a name="Redis List Type">Redis List Type</a></h1>Redis Lists are lists of <a href="Strings.html">Redis Strings</a>, sorted by insertion order. It's possible to add elements to a Redis List pushing new elements on the head (on the left) or on the tail (on the right) of the list.<br/><br/>The <a href="RpushCommand.html">LPUSH</a> command inserts a new elmenet on head, while <a href="RpushCommand.html">RPUSH</a> inserts a new element on tail. A new list is created when one of this operations is performed against an empty key.<br/><br/>For instance if perform the following operations:
	30	<pre class="codeblock python" name="code">
	31	LPUSH mylist a # now the list is "a"
	32	LPUSH mylist b # now the list is "b","a"
	33	RPUSH mylist c # now the list is "b","a","c" (RPUSH was used this time)
	34	</pre>
	35	The resulting list stored at <i>mylist</i> will contain the elements "b","a","c".<br/><br/>The max length of a list is 232-1 elements (4294967295, more than 4 billion of elements per list).<h1><a name="Implementation details">Implementation details</a></h1>Redis Lists are implemented as doubly liked lists. A few commands benefit from the fact the lists are doubly linked in order to reach the needed element starting from the nearest extreme (head or tail). <a href="LrangeCommand.html">LRANGE</a> and <a href="LindexCommand.html">LINDEX</a> are examples of such commands.<br/><br/>The use of linked lists also guarantees that regardless of the length of the list pushing and popping are O(1) operations.<br/><br/>Redis Lists cache length information so <a href="LlenCommand.html">LLEN</a> is O(1) as well.
	36	</div>
	37
	38	</div>
	39	</div>
	40	</body>
	41	</html>
	42