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<b>FromSqlToDataStructures: Contents</b><br>&nbsp;&nbsp;<a href="#Introduction (IDEA MORE THAN A DRAFT)">Introduction (IDEA MORE THAN A DRAFT)</a><br>&nbsp;&nbsp;&nbsp;&nbsp;<a href="#Data Structures">Data Structures</a><br>&nbsp;&nbsp;&nbsp;&nbsp;<a href="#Dude where is my SELECT statement?">Dude where is my SELECT statement?</a><br>&nbsp;&nbsp;&nbsp;&nbsp;<a href="#LISTs">LISTs</a><br>&nbsp;&nbsp;&nbsp;&nbsp;<a href="#SETs">SETs</a><br>&nbsp;&nbsp;&nbsp;&nbsp;<a href="#SORT to the rescue">SORT to the rescue</a><br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<a href="#SORT BY">SORT BY</a><br>&nbsp;&nbsp;&nbsp;&nbsp;<a href="#HASHEs">HASHEs</a>
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<h1><a name="Introduction (IDEA MORE THAN A DRAFT)">Introduction (IDEA MORE THAN A DRAFT)</a></h1><b>&Acirc;&iquest;Coming from SQLand?</b> <i>&Acirc;&iquest;Who doesn't?</i> Redis is simple, <i>primitive</i> when comapred to the world you are used to in the world of Relational Database Managers (RDBMS) and Structure Query Language (SQL), here you will find insight to build bridges between both worlds to model real life problems.<h2><a name="Data Structures">Data Structures</a></h2>When I was young, happy and single ;) I studied <b>Data Structures</b> at the university, actually I learnt Data Structures and Algorithms <i>before</i> learning anything about Databases, and particularly RDBMS and SQL. This is natural because you need to know about Data Structures and Algorithms to understand a Database.<br/><br/>Redis can be seen as a <b>Data Structures Server</b>, a very simple interface to a extremly fast and efficient <h2><a name="Dude where is my SELECT statement?">Dude where is my SELECT statement?</a></h2><h2><a name="LISTs">LISTs</a></h2>In SQL there is no such thing as a &quot;natural&quot; order, a SELECT statement without a ORDER BY clause will return data in a undefined order. In Redis <a href="LISTs.html">LISTs</a> address the problem of natural ordering, ...<h2><a name="SETs">SETs</a></h2>So you have a bunch of unordered data, <h2><a name="SORT to the rescue">SORT to the rescue</a></h2>But sometimes we <i>need</i> to actually sort a LIST in a order different from its natural or take a SET and have it ordered, there is where the <i>fast</i> SORT commands comes handy... <h3><a name="SORT BY">SORT BY</a></h3>Just SORTing keys would be kind of boring, sometimes useless right? Well, you can SORT...<h2><a name="HASHEs">HASHEs</a></h2>Umm, sorry you will have to wait for a <a href="RoadMap.html">upcoming version of Redis</a> to have Hashes, but here are Idioms you should house to manage Dictionary like data...
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&iuml;&raquo;&iquest;== Generic Commands ==<br/><br/><ul><li> <a href="ExistsCommand.html">EXISTS</a></li><li> <a href="DelCommand.html">DEL</a></li><li> <a href="TypeCommand.html">TYPE</a></li><li> <a href="KeysCommand.html">KEYS</a></li><li> <a href="RandomkeyCommand.html">RANDOMKEY</a></li><li> <a href="RenameCommand.html">RENAME</a></li><li> <a href="RenamenxCommand.html">RENAMENX</a></li><li> <a href="DbsizeCommand.html">DBSIZE</a></li><li> <a href="ExpireCommand.html">EXPIRE</a></li><li> <a href="TtlCommand.html">TTL</a></li><li> <a href="SelectCommand.html">SELECT</a></li><li> <a href="MoveCommand.html">MOVE</a></li><li> <a href="FlushdbCommand.html">FLUSHDB</a></li><li> <a href="FlushallCommand.html">FLUSHALL</a></li></ul>
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<b>GetCommand: Contents</b><br>&nbsp;&nbsp;<a href="#GET _key_">GET _key_</a><br>&nbsp;&nbsp;&nbsp;&nbsp;<a href="#Return value">Return value</a>
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&iuml;&raquo;&iquest;#sidebar <a href="StringCommandsSidebar.html">StringCommandsSidebar</a><h1><a name="GET _key_">GET _key_</a></h1>
<i>Time complexity: O(1)</i><blockquote>Get the value of the specified key. If the keydoes not exist the special value 'nil' is returned.If the value stored at <i>key</i> is not a string an erroris returned because GET can only handle string values.</blockquote>
<h2><a name="Return value">Return value</a></h2><a href="ReplyTypes.html">Bulk reply</a>
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<b>GetsetCommand: Contents</b><br>&nbsp;&nbsp;<a href="#GETSET _key_ _value_">GETSET _key_ _value_</a><br>&nbsp;&nbsp;&nbsp;&nbsp;<a href="#Return value">Return value</a><br>&nbsp;&nbsp;&nbsp;&nbsp;<a href="#Design patterns">Design patterns</a>
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&iuml;&raquo;&iquest;#sidebar <a href="StringCommandsSidebar.html">StringCommandsSidebar</a><h1><a name="GETSET _key_ _value_">GETSET _key_ _value_</a></h1>
<i>Time complexity: O(1)</i><blockquote>GETSET is an atomic <i>set this value and return the old value</i> command.Set <i>key</i> to the string <i>value</i> and return the old value stored at <i>key</i>.The string can't be longer than 1073741824 bytes (1 GB).</blockquote>
<h2><a name="Return value">Return value</a></h2><a href="ReplyTypes.html">Bulk reply</a><h2><a name="Design patterns">Design patterns</a></h2><blockquote>GETSET can be used together with INCR for counting with atomic reset whena given condition arises. For example a process may call INCR against thekey <i>mycounter</i> every time some event occurred, but from time totime we need to get the value of the counter and reset it to zero atomicallyusing <code name="code" class="python">GETSET mycounter 0</code>.</blockquote>
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<b>IncrCommand: Contents</b><br>&nbsp;&nbsp;<a href="#INCR _key_">INCR _key_</a><br>&nbsp;&nbsp;<a href="#INCRBY _key_ _integer_">INCRBY _key_ _integer_</a><br>&nbsp;&nbsp;<a href="#DECR _key_ _integer_">DECR _key_ _integer_</a><br>&nbsp;&nbsp;<a href="#DECRBY _key_ _integer_">DECRBY _key_ _integer_</a><br>&nbsp;&nbsp;&nbsp;&nbsp;<a href="#Return value">Return value</a>
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&iuml;&raquo;&iquest;#sidebar <a href="StringCommandsSidebar.html">StringCommandsSidebar</a><h1><a name="INCR _key_">INCR _key_</a></h1>
<h1><a name="INCRBY _key_ _integer_">INCRBY _key_ _integer_</a></h1>
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<h1><a name="DECRBY _key_ _integer_">DECRBY _key_ _integer_</a></h1>
<i>Time complexity: O(1)</i><blockquote>Increment or decrement the number stored at <i>key</i> by one. If the key doesnot exist or contains a value of a wrong type, set the key to thevalue of &quot;0&quot; before to perform the increment or decrement operation.</blockquote>
<blockquote>INCRBY and DECRBY work just like INCR and DECR but instead toincrement/decrement by 1 the increment/decrement is <i>integer</i>.</blockquote>
<blockquote>INCR commands are limited to 64 bit signed integers.</blockquote>
<h2><a name="Return value">Return value</a></h2><a href="ReplyTypes.html">Integer reply</a>, this commands will reply with the new value of <i>key</i> after the increment or decrement.
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<b>InfoCommand: Contents</b><br>&nbsp;&nbsp;<a href="#INFO">INFO</a><br>&nbsp;&nbsp;&nbsp;&nbsp;<a href="#Return value">Return value</a><br>&nbsp;&nbsp;&nbsp;&nbsp;<a href="#Notes">Notes</a>
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&iuml;&raquo;&iquest;#sidebar <a href="ControlCommandsSidebar.html">ControlCommandsSidebar</a><h1><a name="INFO">INFO</a></h1><blockquote>The info command returns different information and statistics about the server in an format that's simple to parse by computers and easy to red by huamns.</blockquote>
<h2><a name="Return value">Return value</a></h2><a href="ReplyTypes.html">Bulk reply</a>, specifically in the following format:<br/><br/><pre class="codeblock python" name="code">
edis_version:0.07
connected_clients:1
connected_slaves:0
used_memory:3187
changes_since_last_save:0
last_save_time:1237655729
total_connections_received:1
total_commands_processed:1
uptime_in_seconds:25
uptime_in_days:0
</pre>All the fields are in the form <code name="code" class="python">field:value</code><h2><a name="Notes">Notes</a></h2><ul><li> <code name="code" class="python">used_memory</code> is returned in bytes, and is the total number of bytes allocated by the program using <code name="code" class="python">malloc</code>.</li><li> <code name="code" class="python">uptime_in_days</code> is redundant since the uptime in seconds contains already the full uptime information, this field is only mainly present for humans.</li><li> <code name="code" class="python">changes_since_last_save</code> does not refer to the number of key changes, but to the number of operations that produced some kind of change in the dataset.</li></ul>
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<b>KeysCommand: Contents</b><br>&nbsp;&nbsp;<a href="#KEYS _pattern_">KEYS _pattern_</a><br>&nbsp;&nbsp;&nbsp;&nbsp;<a href="#Return value">Return value</a>
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<h1 class="wikiname">KeysCommand</h1>
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&iuml;&raquo;&iquest;#sidebar <a href="GenericCommandsSidebar.html">GenericCommandsSidebar</a><h1><a name="KEYS _pattern_">KEYS _pattern_</a></h1>
<i>Time complexity: O(n) (with n being the number of keys in the DB, and assuming keys and pattern of limited length)</i><blockquote>Returns all the keys matching the glob-style <i>pattern</i> asspace separated strings. For example if you have in thedatabase the keys &quot;foo&quot; and &quot;foobar&quot; the command &quot;KEYS foo<code name="code" class="python">*</code>&quot;will return &quot;foo foobar&quot;.</blockquote>
<blockquote>Note that while the time complexity for this operation is O(n)the constant times are pretty low. For example Redis runningon an entry level laptop can scan a 1 million keys databasein 40 milliseconds. <b>Still it's better to consider this one of
<blockquote>the slow commands that may ruin the DB performance if not usedwith care*.</blockquote>
<blockquote>In other words this command is intended only for debugging and *special* operations like creating a script to change the DB schema. Don't use it in your normal code. Use Redis <a href="Sets.html">Sets</a> in order to group together a subset of objects.</blockquote>
Glob style patterns examples:
<blockquote>* h?llo will match hello hallo hhllo* h*llo will match hllo heeeello* h<code name="code" class="python">[</code>ae<code name="code" class="python">]</code>llo will match hello and hallo, but not hillo</blockquote>Use \ to escape special chars if you want to match them verbatim.<h2><a name="Return value">Return value</a></h2><a href="ReplyTypes.html">Bulk reply</a>, specifically a string in the form of space separated list of keys. Note that most client libraries will return an Array of keys and not a single string with space separated keys (that is, split by &quot; &quot; is performed in the client library usually).</b></blockquote>
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<b>LastsaveCommand: Contents</b><br>&nbsp;&nbsp;<a href="#LASTSAVE">LASTSAVE</a><br>&nbsp;&nbsp;&nbsp;&nbsp;<a href="#Return value">Return value</a>
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<h1 class="wikiname">LastsaveCommand</h1>
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&iuml;&raquo;&iquest;#sidebar <a href="ControlCommandsSidebar.html">ControlCommandsSidebar</a><h1><a name="LASTSAVE">LASTSAVE</a></h1>
<blockquote>Return the UNIX TIME of the last DB save executed with success.A client may check if a <a href="BgsaveCommand.html">BGSAVE</a> command succeeded reading the LASTSAVEvalue, then issuing a <a href="BgsaveCommand.html">BGSAVE</a> command and checking at regular intervalsevery N seconds if LASTSAVE changed.</blockquote>
<h2><a name="Return value">Return value</a></h2><a href="ReplyTypes.html">Integer reply</a>, specifically an UNIX time stamp.
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<b>LindexCommand: Contents</b><br>&nbsp;&nbsp;<a href="#LINDEX _key_ _index_">LINDEX _key_ _index_</a><br>&nbsp;&nbsp;&nbsp;&nbsp;<a href="#Return value">Return value</a>
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<h1 class="wikiname">LindexCommand</h1>
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&iuml;&raquo;&iquest;#sidebar <a href="ListCommandsSidebar.html">ListCommandsSidebar</a><h1><a name="LINDEX _key_ _index_">LINDEX _key_ _index_</a></h1>
<i>Time complexity: O(n) (with n being the length of the list)</i><blockquote>Return the specified element of the list stored at the specifiedkey. 0 is the first element, 1 the second and so on. Negative indexesare supported, for example -1 is the last element, -2 the penultimateand so on.</blockquote>
<blockquote>If the value stored at key is not of list type an error is returned.If the index is out of range an empty string is returned.</blockquote>
<blockquote>Note that even if the average time complexity is O(n) asking forthe first or the last element of the list is O(1).</blockquote>
<h2><a name="Return value">Return value</a></h2><a href="ReplyTypes.html">Bulk reply</a>, specifically the requested element.
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<b>ListCommandsSidebar: Contents</b>
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<h1 class="wikiname">ListCommandsSidebar</h1>
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&iuml;&raquo;&iquest;== List Commands ==<br/><br/><ul><li> <a href="RpushCommand.html">RPUSH</a></li><li> <a href="RpushCommand.html">LPUSH</a></li><li> <a href="LlenCommand.html">LLEN</a></li><li> <a href="LrangeCommand.html">LRANGE</a></li><li> <a href="LtrimCommand.html">LTRIM</a></li><li> <a href="LindexCommand.html">LINDEX</a></li><li> <a href="LsetCommand.html">LSET</a></li><li> <a href="LremCommand.html">LREM</a></li><li> <a href="LpopCommand.html">LPOP</a></li><li> <a href="LpopCommand.html">RPOP</a></li><li> <a href="RpoplpushCommand.html">RPOPLPUSH</a></li><li> <a href="SortCommand.html">SORT</a></li></ul>
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<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>
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<h1 class="wikiname">Lists</h1>
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&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)
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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.
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<b>LlenCommand: Contents</b><br>&nbsp;&nbsp;<a href="#LLEN _key_">LLEN _key_</a><br>&nbsp;&nbsp;&nbsp;&nbsp;<a href="#Return value">Return value</a>
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&iuml;&raquo;&iquest;#sidebar <a href="ListCommandsSidebar.html">ListCommandsSidebar</a><h1><a name="LLEN _key_">LLEN _key_</a></h1>
<i>Time complexity: O(1)</i><blockquote>Return the length of the list stored at the specified key. If thekey does not exist zero is returned (the same behaviour as forempty lists). If the value stored at <i>key</i> is not a list an error is returned.</blockquote>
<h2><a name="Return value">Return value</a></h2><a href="ReplyTypes.html">Integer reply</a>, specifically:<br/><br/><pre class="codeblock python" name="code">
The length of the list.
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<b>LpopCommand: Contents</b><br>&nbsp;&nbsp;<a href="#LPOP _key_">LPOP _key_</a><br>&nbsp;&nbsp;<a href="#RPOP _key_">RPOP _key_</a><br>&nbsp;&nbsp;&nbsp;&nbsp;<a href="#Return value">Return value</a>
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<h1 class="wikiname">LpopCommand</h1>
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&iuml;&raquo;&iquest;#sidebar <a href="ListCommandsSidebar.html">ListCommandsSidebar</a><h1><a name="LPOP _key_">LPOP _key_</a></h1>
<h1><a name="RPOP _key_">RPOP _key_</a></h1>
<i>Time complexity: O(1)</i><blockquote>Atomically return and remove the first (LPOP) or last (RPOP) elementof the list. For example if the list contains the elements &quot;a&quot;,&quot;b&quot;,&quot;c&quot; LPOPwill return &quot;a&quot; and the list will become &quot;b&quot;,&quot;c&quot;.</blockquote>
<blockquote>If the <i>key</i> does not exist or the list is already empty the specialvalue 'nil' is returned.</blockquote>
<h2><a name="Return value">Return value</a></h2><a href="ReplyTypes.html">Bulk reply</a>
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<b>LrangeCommand: Contents</b><br>&nbsp;&nbsp;<a href="#LRANGE _key_ _start_ _end_">LRANGE _key_ _start_ _end_</a><br>&nbsp;&nbsp;&nbsp;&nbsp;<a href="#Return value">Return value</a>
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<h1 class="wikiname">LrangeCommand</h1>
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&iuml;&raquo;&iquest;#sidebar <a href="ListCommandsSidebar.html">ListCommandsSidebar</a><h1><a name="LRANGE _key_ _start_ _end_">LRANGE _key_ _start_ _end_</a></h1>
<i>Time complexity: O(n) (with n being the length of the range)</i><blockquote>Return the specified elements of the list stored at the specifiedkey. Start and end are zero-based indexes. 0 is the first elementof the list (the list head), 1 the next element and so on.</blockquote>
<blockquote>For example LRANGE foobar 0 2 will return the first three elementsof the list.</blockquote>
<blockquote>_start_ and <i>end</i> can also be negative numbers indicating offsetsfrom the end of the list. For example -1 is the last element ofthe list, -2 the penultimate element and so on.</blockquote>
<blockquote>Indexes out of range will not produce an error: if start is overthe end of the list, or start <code name="code" class="python">&gt;</code> end, an empty list is returned.If end is over the end of the list Redis will threat it just likethe last element of the list.</blockquote>
<h2><a name="Return value">Return value</a></h2><a href="ReplyTypes.html">Multi bulk reply</a>, specifically a list of elements in the specified range.
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<b>LremCommand: Contents</b><br>&nbsp;&nbsp;<a href="#LREM _key_ _count_ _value_">LREM _key_ _count_ _value_</a><br>&nbsp;&nbsp;&nbsp;&nbsp;<a href="#Return value">Return value</a>
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<h1 class="wikiname">LremCommand</h1>
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&iuml;&raquo;&iquest;#sidebar <a href="ListCommandsSidebar.html">ListCommandsSidebar</a><h1><a name="LREM _key_ _count_ _value_">LREM _key_ _count_ _value_</a></h1>
<i>Time complexity: O(N) (with N being the length of the list)</i><blockquote>Remove the first <i>count</i> occurrences of the <i>value</i> element from the list.If <i>count</i> is zero all the elements are removed. If <i>count</i> is negativeelements are removed from tail to head, instead to go from head to tailthat is the normal behaviour. So for example LREM with count -2 and_hello_ as value to remove against the list (a,b,c,hello,x,hello,hello) willlave the list (a,b,c,hello,x). The number of removed elements is returnedas an integer, see below for more information about the returned value.Note that non existing keys are considered like empty lists by LREM, so LREMagainst non existing keys will always return 0.</blockquote>
<h2><a name="Return value">Return value</a></h2><a href="ReplyTypes.html">Integer Reply</a>, specifically:<br/><br/><pre class="codeblock python" name="code">
The number of removed elements if the operation succeeded
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<b>LsetCommand: Contents</b><br>&nbsp;&nbsp;<a href="#LSET _key_ _index_ _value_">LSET _key_ _index_ _value_</a><br>&nbsp;&nbsp;&nbsp;&nbsp;<a href="#Return value">Return value</a>
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<h1 class="wikiname">LsetCommand</h1>
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&iuml;&raquo;&iquest;#sidebar <a href="ListCommandsSidebar.html">ListCommandsSidebar</a><h1><a name="LSET _key_ _index_ _value_">LSET _key_ _index_ _value_</a></h1>
<i>Time complexity: O(N) (with N being the length of the list)</i><blockquote>Set the list element at <i>index</i> (see LINDEX for information about the_index_ argument) with the new <i>value</i>. Out of range indexes willgenerate an error. Note that setting the first or last elements ofthe list is O(1).</blockquote>
<h2><a name="Return value">Return value</a></h2><a href="ReplyTypes.html">Status code reply</a>
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<b>LtrimCommand: Contents</b><br>&nbsp;&nbsp;<a href="#LTRIM _key_ _start_ _end_">LTRIM _key_ _start_ _end_</a><br>&nbsp;&nbsp;&nbsp;&nbsp;<a href="#Return value">Return value</a>
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<h1 class="wikiname">LtrimCommand</h1>
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&iuml;&raquo;&iquest;#sidebar <a href="ListCommandsSidebar.html">ListCommandsSidebar</a><h1><a name="LTRIM _key_ _start_ _end_">LTRIM _key_ _start_ _end_</a></h1>
<i>Time complexity: O(n) (with n being len of list - len of range)</i><blockquote>Trim an existing list so that it will contain only the specifiedrange of elements specified. Start and end are zero-based indexes.0 is the first element of the list (the list head), 1 the next elementand so on.</blockquote>
<blockquote>For example LTRIM foobar 0 2 will modify the list stored at foobarkey so that only the first three elements of the list will remain.</blockquote>
<blockquote>_start_ and <i>end</i> can also be negative numbers indicating offsetsfrom the end of the list. For example -1 is the last element ofthe list, -2 the penultimate element and so on.</blockquote>
<blockquote>Indexes out of range will not produce an error: if start is overthe end of the list, or start &gt; end, an empty list is left as value.If end over the end of the list Redis will threat it just likethe last element of the list.</blockquote>
<blockquote>Hint: the obvious use of LTRIM is together with LPUSH/RPUSH. For example:</blockquote>
<pre class="codeblock python" name="code">
LPUSH mylist &lt;someelement&gt;
LTRIM mylist 0 99
</pre><blockquote>The above two commands will push elements in the list taking care thatthe list will not grow without limits. This is very useful when usingRedis to store logs for example. It is important to note that when usedin this way LTRIM is an O(1) operation because in the average casejust one element is removed from the tail of the list.</blockquote>
<h2><a name="Return value">Return value</a></h2><a href="ReplyTypes.html">Status code reply</a>
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<b>MgetCommand: Contents</b><br>&nbsp;&nbsp;<a href="#MGET _key1_ _key2_ ... _keyN_">MGET _key1_ _key2_ ... _keyN_</a><br>&nbsp;&nbsp;&nbsp;&nbsp;<a href="#Return value">Return value</a><br>&nbsp;&nbsp;&nbsp;&nbsp;<a href="#Example">Example</a>
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<h1 class="wikiname">MgetCommand</h1>
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&iuml;&raquo;&iquest;#sidebar <a href="StringCommandsSidebar.html">StringCommandsSidebar</a><h1><a name="MGET _key1_ _key2_ ... _keyN_">MGET _key1_ _key2_ ... _keyN_</a></h1>
<i>Time complexity: O(1) for every key</i><blockquote>Get the values of all the specified keys. If one or more keys dont existor is not of type String, a 'nil' value is returned instead of the valueof the specified key, but the operation never fails.</blockquote>
<h2><a name="Return value">Return value</a></h2><a href="ReplyTypes.html">Multi bulk reply</a><h2><a name="Example">Example</a></h2><pre class="codeblock python" name="code">
$ ./redis-cli set foo 1000
+OK
$ ./redis-cli set bar 2000
+OK
$ ./redis-cli mget foo bar
1. 1000
2. 2000
$ ./redis-cli mget foo bar nokey
1. 1000
2. 2000
3. (nil)
$
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<b>MonitorCommand: Contents</b><br>&nbsp;&nbsp;<a href="#MONITOR">MONITOR</a><br>&nbsp;&nbsp;&nbsp;&nbsp;<a href="#Return value">Return value</a>
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<h1 class="wikiname">MonitorCommand</h1>
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&iuml;&raquo;&iquest;#sidebar <a href="ControlCommandsSidebar.html">ControlCommandsSidebar</a><h1><a name="MONITOR">MONITOR</a></h1><blockquote>MONITOR is a debugging command that outputs the whole sequence of commandsreceived by the Redis server. is very handy in order to understandwhat is happening into the database. This command is used directlyvia telnet.</blockquote>
<pre class="codeblock python" name="code">
% telnet 127.0.0.1 6379
Trying 127.0.0.1...
Connected to segnalo-local.com.
Escape character is '^]'.
MONITOR
+OK
monitor
keys *
dbsize
set x 6
foobar
get x
del x
get x
set key_x 5
hello
set key_y 5
hello
set key_z 5
hello
set foo_a 5
hello
</pre><blockquote>The ability to see all the requests processed by the server is useful in orderto spot bugs in the application both when using Redis as a database and asa distributed caching system.</blockquote>
<blockquote>In order to end a monitoring session just issue a QUIT command by hand.</blockquote>
<h2><a name="Return value">Return value</a></h2><b>Non standard return value</b>, just dumps the received commands in an infinite flow.
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