Author: buildbot
Date: Tue Apr 24 18:48:15 2012
New Revision: 814264
Log:
Staging update by buildbot for accumulo
Modified:
websites/staging/accumulo/trunk/content/ (props changed)
websites/staging/accumulo/trunk/content/glossary.html
Propchange: websites/staging/accumulo/trunk/content/
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Modified: websites/staging/accumulo/trunk/content/glossary.html
==============================================================================
--- websites/staging/accumulo/trunk/content/glossary.html (original)
+++ websites/staging/accumulo/trunk/content/glossary.html Tue Apr 24 18:48:15
2012
@@ -89,25 +89,31 @@
<div id="content">
<h1 class="title">Apache Accumulo Glossary</h1>
<ul>
-<li><strong>authorizations</strong> - </li>
-<li><strong>column</strong> - </li>
-<li><strong>column family</strong> - </li>
-<li><strong>column qualifier</strong> - </li>
-<li><strong>column visibility</strong> -</li>
-<li><strong>key</strong> - </li>
-<li><strong>iterator</strong> - </li>
-<li><strong>iterator scopes</strong> - </li>
-<li><strong>log-structured merge-tree</strong> - </li>
-<li><strong>major compaction</strong> - </li>
+<li><strong>authorizations</strong> - a set of strings associated with a user
or with a particular scan that will be used to determine which key/value pairs
are visible to the user.</li>
+<li><strong>cell</strong> - a set of key/value pairs whose keys differ only in
timestamp.</li>
+<li><strong>column</strong> - the portion of the key that sorts after the row
and is divided into family, qualifier, and visibility.</li>
+<li><strong>column family</strong> - the portion of the key that sorts second
and controls locality groups, the row/column hybrid nature of accumulo.</li>
+<li><strong>column qualifier</strong> - the portion of the key that sorts
third and provides additional key uniqueness.</li>
+<li><strong>column visibility</strong> - the portion of the key that sorts
fourth and controls user access to individual key/value pairs. Visibilities are
boolean AND (&) and OR (|) combinations of authorization strings with
parentheses required to determine ordering, e.g. (AB&C)|DEF.</li>
+<li><strong>iterator</strong> - a mechanism for modifying tablet-local
portions of the key/value space. Iterators are used for standard administrative
tasks as well as for custom processing.</li>
+<li><strong>iterator priority</strong> - an iterator must be configured with a
particular scope and priority. When a tablet server enters that scope, it will
instantiate iterators in priority order starting from the smallest priority and
ending with the largest, and apply each to the data read before rewriting the
data or sending the data to the user.</li>
+<li><strong>iterator scopes</strong> - the possible scopes for iterators are
where the tablet server is already reading and/or writing data: minor
compaction / flush time (<em>minc</em> scope), major compaction / file merging
time (<em>majc</em> scope), and query time (<em>scan</em> scope)</li>
+<li><strong>gc</strong> - </li>
+<li><strong>key</strong> - the key into the distributed sorted map which is
accumulo. The key is subdivided into row, column, and timestamp. The column
is further divided into family, qualifier, and visibility.</li>
+<li><strong>locality group</strong> - a set of column families that will be
grouped together on disk. With no locality groups configured, data is stored
on disk in row order. If each column family were configured to be its own
locality group, the data for each column would be stored separately, in row
order. Configuring sets of columns into locality groups is a compromise
between the two approaches and will improve performance when multiple columns
are accessed in the same scan.</li>
+<li><strong>log-structured merge-tree</strong> - the sorting / flushing /
merging scheme on which BigTable's design is based.</li>
+<li><strong>logger</strong> - </li>
+<li><strong>major compaction</strong> - merging multiple files into a single
file. If all of a tablet's files are merged into a single file, it is called a
<em>full major compaction</em>.</li>
<li><strong>master</strong> - </li>
-<li><strong>minor compaction</strong> - </li>
-<li><strong>permissions</strong> - </li>
-<li><strong>row</strong> - </li>
-<li><strong>scan</strong> -</li>
-<li><strong>tablet</strong> - a contiguous key range; the unit of work for a
tablet server</li>
-<li><strong>tablet server</strong> - </li>
-<li><strong>timestamp</strong> - </li>
-<li><strong>value</strong> - </li>
+<li><strong>minor compaction</strong> - flushing data from memory to disk.
Usually this creates a new file for a tablet, but if the memory flushed is
merge-sorted in with data from an existing file (replacing that file), it is
called a <em>merging minor compaction</em>.</li>
+<li><strong>monitor</strong> -</li>
+<li><strong>permissions</strong> - administrative abilities that must be given
to a user such as creating tables or users and changing permissions or
configuration parameters.</li>
+<li><strong>row</strong> - the portion of the key that is controls atomicity.
Keys with the same row are guaranteed to remain on a single tablet hosted by a
single tablet server, therefore multiple key/value pairs can be added to or
removed from a row at the same time. The row is used for the primary sorting of
the key.</li>
+<li><strong>scan</strong> - reading a range of key/value pairs.</li>
+<li><strong>tablet</strong> - a contiguous key range; the unit of work for a
tablet server.</li>
+<li><strong>tablet servers</strong> - a set of servers that hosts reads and
writes for tablets. Each server hosts a distinct set of tablets at any given
time, but the tablets may be hosted by different servers over time.</li>
+<li><strong>timestamp</strong> - the portion of the key that controls
versioning. Otherwise identical keys with differing timestamps are considered
to be versions of a single <em>cell</em>. Accumulo can be configured to keep
the <em>N</em> newest versions of each <em>cell</em>. When a deletion entry is
inserted, it deletes all earlier versions for its cell.</li>
+<li><strong>value</strong> - immutable bytes associated with a particular
key.</li>
</ul>
</div>
