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Kenneth Reitz
36 lines
1.6 KiB
ReStructuredText
36 lines
1.6 KiB
ReStructuredText
`|Redis Documentation| <index.html>`_
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**SetbitCommand: Contents**
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`SETBIT \_key\_ \_offset\_ \_value\_ (Redis > <#SETBIT%20_key_%20_offset_%20_value_%20(Redis%20%3E>`_
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`Return value <#Return%20value>`_
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SetbitCommand
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=============
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SETBIT \_key\_ \_offset\_ \_value\_ (Redis >
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============================================
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2.1.8) = *Time complexity: O(1)*
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Sets or clears the bit at *offset* in the string value stored at
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*key*.
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The bit is either set or cleared depending on *value*, which can be
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either 0 or 1. When *key* does not exist, a new string value is
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created. The string is grown to make sure it can hold a bit at
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*offset*. The *offset* argument is required to be greater than or
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equal to 0, and is limited to
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2\ :sup:`32-1 (which limits bitmaps to 512MB). When the string at *key* is grown, added bits are set to 0.**Warning**: When setting the last possible bit (*offset* equal to 2`\ 32-1)
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and the string value stored at *key* does not yet hold a string
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value, or holds a small string value, Redis needs to allocate all
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intermediate memory which can block the server for some time. On a
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2010 Macbook Pro, setting bit number
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2\ :sup:`32-1 (512MB allocation) takes ~300ms, setting bit number 2`\ 30-1
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(128MB allocation) takes ~80ms, setting bit number
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2\ :sup:`28-1 (32MB allocation) takes ~30ms and setting bit number 2`\ 26-1
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(8MB allocation) takes ~8ms. Note that once this first allocation
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is done, subsequent calls to SETBIT for the same *key* will not
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have the allocation overhead.
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Return value
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------------
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`Integer reply <ReplyTypes.html>`_, specifically: the original bit
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value stored at *offset*.
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.. |Redis Documentation| image:: redis.png |