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From: Tyler Hobbs <tyler@datastax.com>
Date: Fri, 2 Jan 2015 13:35:04 -0600
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Subject: 
 =?UTF-8?Q?Re=3A_is_primary_key=28_foo=2C_bar=29_the_same_as_primary_ke?=
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To: user@cassandra.apache.org
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On Fri, Jan 2, 2015 at 1:13 PM, Eric Stevens <mightye@gmail.com> wrote:

> > And also stored entirely for each UPDATE. Change one element,
> re-serialize the whole thing to disk.
>
> Is this true?  I thought updates (adds, removes, but not overwrites)
> affected just the indicated columns.  Isn't it just the reads that involve
> reading the entire collection?


This is not true (with one minor exception).  All operations on sets and
maps require no reads.  The same is true for appends and prepends on lists,
but delete and set operations on lists with (non-zero) indexes require the
list to be read first.  However, the entire list does not need to be
re-written to disk.

-- 
Tyler Hobbs
DataStax <http://datastax.com/>

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<div dir=3D"ltr"><div class=3D"gmail_extra"><br><div class=3D"gmail_quote">=
On Fri, Jan 2, 2015 at 1:13 PM, Eric Stevens <span dir=3D"ltr">&lt;<a href=
=3D"mailto:mightye@gmail.com" target=3D"_blank">mightye@gmail.com</a>&gt;</=
span> wrote:<br><blockquote class=3D"gmail_quote" style=3D"margin:0 0 0 .8e=
x;border-left:1px #ccc solid;padding-left:1ex"><span class=3D""><div>&gt;=
=C2=A0<span style=3D"font-size:13px">And also stored entirely for each UPDA=
TE. Change one element, re-serialize the whole thing to disk.</span></div><=
div><br></div></span>Is this true?=C2=A0 I thought updates (adds, removes, =
but not overwrites) affected just the indicated columns.=C2=A0 Isn&#39;t it=
 just the reads that involve reading the entire collection?</blockquote></d=
iv><br></div><div class=3D"gmail_extra">This is not true (with one minor ex=
ception).=C2=A0 All operations on sets and maps require no reads.=C2=A0 The=
 same is true for appends and prepends on lists, but delete and set operati=
ons on lists with (non-zero) indexes require the list to be read first.=C2=
=A0 However, the entire list does not need to be re-written to disk.<br cle=
ar=3D"all"><br>-- <br><div class=3D"gmail_signature"><font color=3D"#888888=
">Tyler Hobbs<span></span><br>
<a href=3D"http://datastax.com/" target=3D"_blank">DataStax</a><br></font><=
/div>
</div></div>

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