[redis.git] / doc / SetbitCommand.html


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<b>SetbitCommand: Contents</b><br>&nbsp;&nbsp;<a href="#SETBIT _key_ _offset_ _value_ (Redis &gt;">SETBIT _key_ _offset_ _value_ (Redis &gt;</a><br>&nbsp;&nbsp;&nbsp;&nbsp;<a href="#Return value">Return value</a>
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                <h1 class="wikiname">SetbitCommand</h1>

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<h1><a name="SETBIT _key_ _offset_ _value_ (Redis &gt;">SETBIT _key_ _offset_ _value_ (Redis &gt;</a></h1> 2.1.8) =
<i>Time complexity: O(1)</i><blockquote>Sets or clears the bit at <i>offset</i> in the string value stored at <i>key</i>.</blockquote>
The bit is either set or cleared depending on <i>value</i>, which can be either 0 or 1. When <i>key</i> does not exist, a new string value is created. The string is grown to make sure it can hold a bit at <i>offset</i>. The <i>offset</i> argument is required to be greater than or equal to 0, and is limited to 2<sup>32-1 (which limits bitmaps to 512MB).
When the string at <i>key</i> is grown, added bits are set to 0.<br/><br/><b>Warning</b>: When setting the last possible bit (<i>offset</i> equal to 2</sup>32-1) and the string value stored at <i>key</i> does not yet hold a string value, or holds a small string value, Redis needs to allocate all intermediate memory which can block the server for some time.
On a 2010 Macbook Pro, setting bit number 2<sup>32-1 (512MB allocation) takes ~300ms,
setting bit number 2</sup>30-1 (128MB allocation) takes ~80ms,
setting bit number 2<sup>28-1 (32MB allocation) takes ~30ms and
setting bit number 2</sup>26-1 (8MB allocation) takes ~8ms.
Note that once this first allocation is done, subsequent calls to SETBIT for the same <i>key</i> will not have the allocation overhead.<h2><a name="Return value">Return value</a></h2><a href="ReplyTypes.html">Integer reply</a>, specifically: the original bit value stored at <i>offset</i>.
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	18	<!-- This is a (PRE) block. Make sure it's left aligned or your toc title will be off. -->
	19	<b>SetbitCommand: Contents</b><br>  <a href="#SETBIT _key_ _offset_ _value_ (Redis >">SETBIT _key_ _offset_ _value_ (Redis ></a><br>    <a href="#Return value">Return value</a>
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	22	<h1 class="wikiname">SetbitCommand</h1>
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	24	<div class="summary">
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	26	</div>
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	28	<div class="narrow">
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	30	<h1><a name="SETBIT _key_ _offset_ _value_ (Redis >">SETBIT _key_ _offset_ _value_ (Redis ></a></h1> 2.1.8) =
	31	<i>Time complexity: O(1)</i><blockquote>Sets or clears the bit at <i>offset</i> in the string value stored at <i>key</i>.</blockquote>
	32	The bit is either set or cleared depending on <i>value</i>, which can be either 0 or 1. When <i>key</i> does not exist, a new string value is created. The string is grown to make sure it can hold a bit at <i>offset</i>. The <i>offset</i> argument is required to be greater than or equal to 0, and is limited to 2<sup>32-1 (which limits bitmaps to 512MB).
	33	When the string at <i>key</i> is grown, added bits are set to 0.<br/><br/><b>Warning</b>: When setting the last possible bit (<i>offset</i> equal to 2</sup>32-1) and the string value stored at <i>key</i> does not yet hold a string value, or holds a small string value, Redis needs to allocate all intermediate memory which can block the server for some time.
	34	On a 2010 Macbook Pro, setting bit number 2<sup>32-1 (512MB allocation) takes ~300ms,
	35	setting bit number 2</sup>30-1 (128MB allocation) takes ~80ms,
	36	setting bit number 2<sup>28-1 (32MB allocation) takes ~30ms and
	37	setting bit number 2</sup>26-1 (8MB allocation) takes ~8ms.
	38	Note that once this first allocation is done, subsequent calls to SETBIT for the same <i>key</i> will not have the allocation overhead.<h2><a name="Return value">Return value</a></h2><a href="ReplyTypes.html">Integer reply</a>, specifically: the original bit value stored at <i>offset</i>.
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