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svn commit: r1650326 [2/2] - in /tajo/site/docs/current: index/
index/future_work.html index/how_to_use.html index/types.html
index_overview.html table_management/table_overview.html time_zone.html
Added: tajo/site/docs/current/time_zone.html
URL: http://svn.apache.org/viewvc/tajo/site/docs/current/time_zone.html?rev=1650326&view=auto
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--- tajo/site/docs/current/time_zone.html (added)
+++ tajo/site/docs/current/time_zone.html Thu Jan 8 16:28:15 2015
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+<li class="toctree-l1 current"><a class="current reference internal" href="">Time Zone</a><ul>
+<li class="toctree-l2"><a class="reference internal" href="#server-cluster-time-zone">Server Cluster Time Zone</a></li>
+<li class="toctree-l2"><a class="reference internal" href="#table-time-zone">Table Time Zone</a></li>
+<li class="toctree-l2"><a class="reference internal" href="#client-time-zone">Client Time Zone</a></li>
+<li class="toctree-l2"><a class="reference internal" href="#time-zone-id">Time Zone ID</a></li>
+<li class="toctree-l2"><a class="reference internal" href="#examples-of-time-zone">Examples of Time Zone</a></li>
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+ <li>Time Zone</li>
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+
+ <div class="section" id="time-zone">
+<h1>Time Zone<a class="headerlink" href="#time-zone" title="Permalink to this headline">¶</a></h1>
+<p>Time zone affects some data types (e.g., <tt class="docutils literal"><span class="pre">Timestamp</span></tt> and <tt class="docutils literal"><span class="pre">Time</span></tt>) and operations (e.g., <tt class="docutils literal"><span class="pre">to_char</span></tt>). Tables can have different time zones. Internally, Tajo translates all table rows to UTC values and processes them. It becomes easier for Tajo to handle multiple different time zones.</p>
+<p>In Tajo, there are some time zong settings.</p>
+<div class="section" id="server-cluster-time-zone">
+<h2>Server Cluster Time Zone<a class="headerlink" href="#server-cluster-time-zone" title="Permalink to this headline">¶</a></h2>
+<p>One Tajo cluster has a system time zone which globally affects all tables in which the table property ‘time zone’ are not specified.</p>
+<p>You can set the system time zone in <em>conf/tajo-site.xml</em> file as follows:</p>
+<p><strong>tajo-site.xml</strong></p>
+<div class="highlight-xml"><div class="highlight"><pre><span class="nt"><name></span>tajo.timezone<span class="nt"></name></span>
+<span class="nt"><property></span>GMT+9<span class="nt"></property></span>
+</pre></div>
+</div>
+</div>
+<div class="section" id="table-time-zone">
+<h2>Table Time Zone<a class="headerlink" href="#table-time-zone" title="Permalink to this headline">¶</a></h2>
+<p>In Tajo, a table property <tt class="docutils literal"><span class="pre">timezone</span></tt> allows users to specify a time zone that the table uses for reading or writing.
+When each table row are read or written, <tt class="docutils literal"><span class="pre">`timestamp`</span></tt> and <tt class="docutils literal"><span class="pre">`time`</span></tt> column values are adjusted by a given time zone if it is set.</p>
+<p>You can specify a table time zone as follows:</p>
+<div class="highlight-sql"><div class="highlight"><pre><span class="k">CREATE</span> <span class="k">EXTERNAL</span> <span class="k">TABLE</span> <span class="n">table1</span> <span class="p">(</span>
+ <span class="n">t_timestamp</span> <span class="k">TIMESTAMP</span><span class="p">,</span>
+ <span class="n">t_date</span> <span class="nb">DATE</span>
+<span class="p">)</span> <span class="k">USING</span> <span class="nb">TEXT</span> <span class="k">WITH</span><span class="p">(</span><span class="s1">'timezone'</span><span class="o">=</span><span class="s1">'ASIA/Seoul'</span><span class="p">)</span> <span class="k">LOCATION</span> <span class="s1">'/path-to-table/'</span>
+</pre></div>
+</div>
+<p>In order to learn table properties, please refer to <a class="reference internal" href="table_management/table_overview.html"><em>Overview of Tajo Tables</em></a>.</p>
+</div>
+<div class="section" id="client-time-zone">
+<h2>Client Time Zone<a class="headerlink" href="#client-time-zone" title="Permalink to this headline">¶</a></h2>
+<p>Each client has its own time zone setting. It translates retrieved timestamp and time values by time zone. In order to set client time zone, you should set the session variable <tt class="docutils literal"><span class="pre">TIMEZONE</span></tt>. There are some ways to set this session variable.</p>
+<p>In <tt class="docutils literal"><span class="pre">tsql</span></tt>, you can use <tt class="docutils literal"><span class="pre">\set</span> <span class="pre">timezone</span></tt> meta command as follows:</p>
+<p><strong>tsql</strong></p>
+<div class="highlight-sh"><div class="highlight"><pre>default> <span class="se">\s</span>et timezone GMT+9
+</pre></div>
+</div>
+<p>The following ways use SQL statements. So, this way is available in <tt class="docutils literal"><span class="pre">tsql</span></tt>, JDBC, and Tajo Java API.</p>
+<p><strong>SQL</strong></p>
+<div class="highlight-sql"><div class="highlight"><pre><span class="k">SET</span> <span class="n">TIME</span> <span class="k">ZONE</span> <span class="s1">'GMT+9'</span><span class="p">;</span>
+
+<span class="k">or</span>
+
+<span class="k">SET</span> <span class="k">SESSION</span> <span class="n">TIMEZONE</span> <span class="k">TO</span> <span class="s1">'GMT+9'</span><span class="p">;</span>
+</pre></div>
+</div>
+</div>
+<div class="section" id="time-zone-id">
+<h2>Time Zone ID<a class="headerlink" href="#time-zone-id" title="Permalink to this headline">¶</a></h2>
+<p>Time zone can be an abbreviation form like ‘PST’ or ‘DST’. Also, it accepts an offset-based form like ‘GMT+9’ or UTC+9’ or a location-based form like ‘Asia/Seoul’.</p>
+<div class="admonition note">
+<p class="first admonition-title">Note</p>
+<p class="last">In many cases, offset-based forms or locaion-based forms are recommanded. In order to know the list of time zones, please refer to <a class="reference external" href="http://en.wikipedia.org/wiki/List_of_tz_database_time_zones">List of tz database time zones</a></p>
+</div>
+<div class="admonition note">
+<p class="first admonition-title">Note</p>
+<p class="last">Java 6 does not recognize many location-based time zones and an offset-based timezone using the prefix ‘UTC’. We highly recommanded using the offset-based time zone using the prefix ‘GMT’. In other words, you should use ‘GMT-7’ instead of ‘UTC-7’ in Java 6.</p>
+</div>
+</div>
+<div class="section" id="examples-of-time-zone">
+<h2>Examples of Time Zone<a class="headerlink" href="#examples-of-time-zone" title="Permalink to this headline">¶</a></h2>
+<p>For example, consider that there is a list of delimited text lines where each rows are written with <tt class="docutils literal"><span class="pre">Asia/Seoul</span></tt> time zone (i.e., GMT + 9).</p>
+<div class="highlight-text"><div class="highlight"><pre>1980-4-1 01:50:30.010|1980-04-01
+80/4/1 1:50:30 AM|80/4/1
+1980 April 1 1:50:30|1980-04-01
+</pre></div>
+</div>
+<p>In order to register the table, we should put a table property <tt class="docutils literal"><span class="pre">'timezone'='Asia/Seoul'</span></tt> in <tt class="docutils literal"><span class="pre">CREATE</span> <span class="pre">TABLE</span></tt> statement as follows:</p>
+<div class="highlight-sql"><div class="highlight"><pre><span class="k">CREATE</span> <span class="k">EXTERNAL</span> <span class="k">TABLE</span> <span class="n">table1</span> <span class="p">(</span>
+ <span class="n">t_timestamp</span> <span class="k">TIMESTAMP</span><span class="p">,</span>
+ <span class="n">t_date</span> <span class="nb">DATE</span>
+<span class="p">)</span> <span class="k">USING</span> <span class="nb">TEXT</span> <span class="k">WITH</span><span class="p">(</span><span class="s1">'text.delimiter'</span><span class="o">=</span><span class="s1">'|'</span><span class="p">,</span> <span class="s1">'timezone'</span><span class="o">=</span><span class="s1">'ASIA/Seoul'</span><span class="p">)</span> <span class="k">LOCATION</span> <span class="s1">'/path-to-table/'</span>
+</pre></div>
+</div>
+<p>By default, <tt class="docutils literal"><span class="pre">tsql</span></tt> and <tt class="docutils literal"><span class="pre">TajoClient</span></tt> API use UTC time zone. So, timestamp values in the result are adjusted by the time zone offset. But, date is not adjusted because date type does not consider time zone.</p>
+<div class="highlight-sql"><div class="highlight"><pre><span class="k">default</span><span class="o">></span> <span class="k">SELECT</span> <span class="o">*</span> <span class="k">FROM</span> <span class="n">table1</span>
+<span class="n">t_timestamp</span><span class="p">,</span> <span class="n">t_date</span>
+<span class="c1">----------------------------------</span>
+<span class="mi">1980</span><span class="o">-</span><span class="mi">03</span><span class="o">-</span><span class="mi">31</span> <span class="mi">16</span><span class="p">:</span><span class="mi">50</span><span class="p">:</span><span class="mi">30</span><span class="p">.</span><span class="mi">01</span><span class="p">,</span> <span class="mi">1980</span><span class="o">-</span><span class="mi">04</span><span class="o">-</span><span class="mi">01</span>
+<span class="mi">1980</span><span class="o">-</span><span class="mi">03</span><span class="o">-</span><span class="mi">31</span> <span class="mi">16</span><span class="p">:</span><span class="mi">50</span><span class="p">:</span><span class="mi">30</span> <span class="p">,</span> <span class="mi">1980</span><span class="o">-</span><span class="mi">04</span><span class="o">-</span><span class="mi">01</span>
+<span class="mi">1980</span><span class="o">-</span><span class="mi">03</span><span class="o">-</span><span class="mi">31</span> <span class="mi">16</span><span class="p">:</span><span class="mi">50</span><span class="p">:</span><span class="mi">30</span> <span class="p">,</span> <span class="mi">1980</span><span class="o">-</span><span class="mi">04</span><span class="o">-</span><span class="mi">01</span>
+</pre></div>
+</div>
+<p>In addition, users can set client-side time zone by setting a session variable ‘TZ’. It enables a client to translate timestamp or time values to user’s time zoned ones.</p>
+<div class="highlight-sql"><div class="highlight"><pre><span class="k">default</span><span class="o">></span> <span class="k">SET</span> <span class="n">TIME</span> <span class="k">ZONE</span> <span class="s1">'Asia/Seoul'</span>
+<span class="k">default</span><span class="o">></span> <span class="k">SELECT</span> <span class="o">*</span> <span class="k">FROM</span> <span class="n">table1</span>
+<span class="n">t_timestamp</span><span class="p">,</span> <span class="n">t_date</span>
+<span class="c1">----------------------------------</span>
+<span class="mi">1980</span><span class="o">-</span><span class="mi">04</span><span class="o">-</span><span class="mi">01</span> <span class="mi">01</span><span class="p">:</span><span class="mi">50</span><span class="p">:</span><span class="mi">30</span><span class="p">.</span><span class="mi">01</span><span class="p">,</span> <span class="mi">1980</span><span class="o">-</span><span class="mi">04</span><span class="o">-</span><span class="mi">01</span>
+<span class="mi">1980</span><span class="o">-</span><span class="mi">04</span><span class="o">-</span><span class="mi">01</span> <span class="mi">01</span><span class="p">:</span><span class="mi">50</span><span class="p">:</span><span class="mi">30</span> <span class="p">,</span> <span class="mi">1980</span><span class="o">-</span><span class="mi">04</span><span class="o">-</span><span class="mi">01</span>
+<span class="mi">1980</span><span class="o">-</span><span class="mi">04</span><span class="o">-</span><span class="mi">01</span> <span class="mi">01</span><span class="p">:</span><span class="mi">50</span><span class="p">:</span><span class="mi">30</span> <span class="p">,</span> <span class="mi">1980</span><span class="o">-</span><span class="mi">04</span><span class="o">-</span><span class="mi">01</span>
+</pre></div>
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