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Lu, Huayi e6fa411af0 DWS DEV 830.201 version 
Reviewed-by: Pruthi, Vineet <vineet.pruthi@t-systems.com>
Co-authored-by: Lu, Huayi <luhuayi@huawei.com>
Co-committed-by: Lu, Huayi <luhuayi@huawei.com>
2024-05-16 07:24:04 +00:00

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<a name="EN-US_TOPIC_0000001445186320"></a><a name="EN-US_TOPIC_0000001445186320"></a>
<h1 class="topictitle1">Functional Functions</h1>
<div id="body0000001445186320"><div class="section" id="EN-US_TOPIC_0000001445186320__section17339725320"><h4 class="sectiontitle">hll_print(hll)</h4><p id="EN-US_TOPIC_0000001445186320__p123394253216">Description: Prints some debugging parameters of an HLL.</p>
<p id="EN-US_TOPIC_0000001445186320__p13896142812519">Return type: cstring</p>
<p id="EN-US_TOPIC_0000001445186320__p6339125126">Example:</p>
<div class="codecoloring" codetype="Sql" id="EN-US_TOPIC_0000001445186320__screen533915251221"><div class="highlight"><table class="highlighttable"><tr><td class="linenos"><div class="linenodiv"><pre><span class="normal">1</span>
<span class="normal">2</span>
<span class="normal">3</span>
<span class="normal">4</span>
<span class="normal">5</span></pre></div></td><td class="code"><div><pre><span></span><span class="k">SELECT</span><span class="w"> </span><span class="n">hll_print</span><span class="p">(</span><span class="n">hll_empty</span><span class="p">());</span>
<span class="w"> </span><span class="n">hll_print</span><span class="w"> </span>
<span class="c1">-----------------------------------------------------------</span>
<span class="w"> </span><span class="n">EMPTY</span><span class="p">,</span><span class="w"> </span><span class="n">nregs</span><span class="o">=</span><span class="mi">2048</span><span class="p">,</span><span class="w"> </span><span class="n">nbits</span><span class="o">=</span><span class="mi">5</span><span class="p">,</span><span class="w"> </span><span class="n">expthresh</span><span class="o">=-</span><span class="mi">1</span><span class="p">(</span><span class="mi">160</span><span class="p">),</span><span class="w"> </span><span class="n">sparseon</span><span class="o">=</span><span class="mi">1</span><span class="n">gongne</span>
<span class="p">(</span><span class="mi">1</span><span class="w"> </span><span class="k">row</span><span class="p">)</span>
</pre></div></td></tr></table></div>
</div>
</div>
<div class="section" id="EN-US_TOPIC_0000001445186320__section126791722329"><h4 class="sectiontitle">hll_empty()</h4><p id="EN-US_TOPIC_0000001445186320__p56737225216">Description: Creates an empty HLL.</p>
<p id="EN-US_TOPIC_0000001445186320__p36738221215">Return type: hll</p>
<p id="EN-US_TOPIC_0000001445186320__p16673822224">Example:</p>
<div class="codecoloring" codetype="Sql" id="EN-US_TOPIC_0000001445186320__screen1667414222211"><div class="highlight"><table class="highlighttable"><tr><td class="linenos"><div class="linenodiv"><pre><span class="normal">1</span>
<span class="normal">2</span>
<span class="normal">3</span>
<span class="normal">4</span>
<span class="normal">5</span></pre></div></td><td class="code"><div><pre><span></span><span class="k">SELECT</span><span class="w"> </span><span class="n">hll_empty</span><span class="p">();</span>
<span class="w"> </span><span class="n">hll_empty</span><span class="w"> </span>
<span class="c1">-----------</span>
<span class="w"> </span><span class="err">\</span><span class="n">x118b7f</span>
<span class="p">(</span><span class="mi">1</span><span class="w"> </span><span class="k">row</span><span class="p">)</span>
</pre></div></td></tr></table></div>
</div>
</div>
<div class="section" id="EN-US_TOPIC_0000001445186320__section172021629235"><h4 class="sectiontitle">hll_empty(int32 log2m)</h4><p id="EN-US_TOPIC_0000001445186320__p719662918313">Description: Creates an empty HLL and sets the <strong id="EN-US_TOPIC_0000001445186320__b134604510994210">log2m</strong> parameter. The parameter value ranges from 10 to 16.</p>
<p id="EN-US_TOPIC_0000001445186320__p1719652910310">Return type: hll</p>
<p id="EN-US_TOPIC_0000001445186320__p81967291233">Example:</p>
<div class="codecoloring" codetype="Sql" id="EN-US_TOPIC_0000001445186320__screen8196182918317"><div class="highlight"><table class="highlighttable"><tr><td class="linenos"><div class="linenodiv"><pre><span class="normal">1</span>
<span class="normal">2</span>
<span class="normal">3</span>
<span class="normal">4</span>
<span class="normal">5</span></pre></div></td><td class="code"><div><pre><span></span><span class="k">SELECT</span><span class="w"> </span><span class="n">hll_empty</span><span class="p">(</span><span class="mi">10</span><span class="p">);</span>
<span class="w"> </span><span class="n">hll_empty</span><span class="w"> </span>
<span class="c1">-----------</span>
<span class="w"> </span><span class="err">\</span><span class="n">x118a7f</span>
<span class="p">(</span><span class="mi">1</span><span class="w"> </span><span class="k">row</span><span class="p">)</span>
</pre></div></td></tr></table></div>
</div>
</div>
<div class="section" id="EN-US_TOPIC_0000001445186320__section137971131730"><h4 class="sectiontitle">hll_empty(int32 log2m, int32 regwidth)</h4><p id="EN-US_TOPIC_0000001445186320__p879310318313">Description: Creates an empty HLL and sets the <strong id="EN-US_TOPIC_0000001445186320__b124134111494210">log2m</strong> and <strong id="EN-US_TOPIC_0000001445186320__b183405549394210">regwidth</strong> parameters in sequence. The value of <strong id="EN-US_TOPIC_0000001445186320__b130900881994210">regwidth</strong> ranges from 1 to 5.</p>
<p id="EN-US_TOPIC_0000001445186320__p1679314311936">Return type: hll</p>
<p id="EN-US_TOPIC_0000001445186320__p197937311537">Example:</p>
<div class="codecoloring" codetype="Sql" id="EN-US_TOPIC_0000001445186320__screen2794193112312"><div class="highlight"><table class="highlighttable"><tr><td class="linenos"><div class="linenodiv"><pre><span class="normal">1</span>
<span class="normal">2</span>
<span class="normal">3</span>
<span class="normal">4</span>
<span class="normal">5</span></pre></div></td><td class="code"><div><pre><span></span><span class="k">SELECT</span><span class="w"> </span><span class="n">hll_empty</span><span class="p">(</span><span class="mi">10</span><span class="p">,</span><span class="w"> </span><span class="mi">4</span><span class="p">);</span>
<span class="w"> </span><span class="n">hll_empty</span><span class="w"> </span>
<span class="c1">-----------</span>
<span class="w"> </span><span class="err">\</span><span class="n">x116a7f</span>
<span class="p">(</span><span class="mi">1</span><span class="w"> </span><span class="k">row</span><span class="p">)</span>
</pre></div></td></tr></table></div>
</div>
</div>
<div class="section" id="EN-US_TOPIC_0000001445186320__section724419361631"><h4 class="sectiontitle">hll_empty(int32 log2m, int32 regwidth, int64 expthresh)</h4><p id="EN-US_TOPIC_0000001445186320__p152408361739">Description: Creates an empty HLL and sets the <strong id="EN-US_TOPIC_0000001445186320__b86089753994210">log2m</strong>, <strong id="EN-US_TOPIC_0000001445186320__b166511284994210">regwidth</strong>, and <strong id="EN-US_TOPIC_0000001445186320__b205741450494210">expthresh</strong> parameters. The value of <strong id="EN-US_TOPIC_0000001445186320__b209415374894210">expthresh</strong> is an integer ranging from –1 to 7. This parameter specifies the threshold for switching from the <strong id="EN-US_TOPIC_0000001445186320__b7777173894210">explicit</strong> mode to the <strong id="EN-US_TOPIC_0000001445186320__b126583708994210">sparse</strong> mode. <strong id="EN-US_TOPIC_0000001445186320__b42234075294210">–1</strong> indicates the auto mode; <strong id="EN-US_TOPIC_0000001445186320__b197428906194210">0</strong> indicates that the <strong id="EN-US_TOPIC_0000001445186320__b108501067594210">explicit</strong> mode is skipped; a value from 1 to 7 indicates that the mode is switched when the number of distinct values reaches 2<sup id="EN-US_TOPIC_0000001445186320__sup189660049794210"><strong id="EN-US_TOPIC_0000001445186320__b19460042494210">expthresh</strong></sup>.</p>
<p id="EN-US_TOPIC_0000001445186320__p324020368318">Return type: hll</p>
<p id="EN-US_TOPIC_0000001445186320__p192406362316">Example:</p>
<div class="codecoloring" codetype="Sql" id="EN-US_TOPIC_0000001445186320__screen62411366312"><div class="highlight"><table class="highlighttable"><tr><td class="linenos"><div class="linenodiv"><pre><span class="normal">1</span>
<span class="normal">2</span>
<span class="normal">3</span>
<span class="normal">4</span>
<span class="normal">5</span></pre></div></td><td class="code"><div><pre><span></span><span class="k">SELECT</span><span class="w"> </span><span class="n">hll_empty</span><span class="p">(</span><span class="mi">10</span><span class="p">,</span><span class="w"> </span><span class="mi">4</span><span class="p">,</span><span class="w"> </span><span class="mi">7</span><span class="p">);</span>
<span class="w"> </span><span class="n">hll_empty</span><span class="w"> </span>
<span class="c1">-----------</span>
<span class="w"> </span><span class="err">\</span><span class="n">x116a48</span>
<span class="p">(</span><span class="mi">1</span><span class="w"> </span><span class="k">row</span><span class="p">)</span>
</pre></div></td></tr></table></div>
</div>
</div>
<div class="section" id="EN-US_TOPIC_0000001445186320__section10108939737"><h4 class="sectiontitle">hll_empty(int32 log2m, int32 regwidth, int64 expthresh, int32 sparseon)</h4><p id="EN-US_TOPIC_0000001445186320__p17104739332">Description: Creates an empty HLL and sets the <strong id="EN-US_TOPIC_0000001445186320__b114343855394210">log2m</strong>, <strong id="EN-US_TOPIC_0000001445186320__b109896469494210">regwidth</strong>, <strong id="EN-US_TOPIC_0000001445186320__b1091340694210">expthresh</strong>, and <strong id="EN-US_TOPIC_0000001445186320__b41859855094210">sparseon</strong> parameters. The value of <strong id="EN-US_TOPIC_0000001445186320__b17281766094210">sparseon</strong> is <strong id="EN-US_TOPIC_0000001445186320__b5167285494210">0</strong> or <strong id="EN-US_TOPIC_0000001445186320__b108531592594210">1</strong>.</p>
<p id="EN-US_TOPIC_0000001445186320__p171045391734">Return type: hll</p>
<p id="EN-US_TOPIC_0000001445186320__p910413399316">Example:</p>
<div class="codecoloring" codetype="Sql" id="EN-US_TOPIC_0000001445186320__screen810514392037"><div class="highlight"><table class="highlighttable"><tr><td class="linenos"><div class="linenodiv"><pre><span class="normal">1</span>
<span class="normal">2</span>
<span class="normal">3</span>
<span class="normal">4</span>
<span class="normal">5</span></pre></div></td><td class="code"><div><pre><span></span><span class="k">SELECT</span><span class="w"> </span><span class="n">hll_empty</span><span class="p">(</span><span class="mi">10</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">7</span><span class="p">,</span><span class="mi">0</span><span class="p">);</span>
<span class="w"> </span><span class="n">hll_empty</span><span class="w"> </span>
<span class="c1">-----------</span>
<span class="w"> </span><span class="err">\</span><span class="n">x116a08</span>
<span class="p">(</span><span class="mi">1</span><span class="w"> </span><span class="k">row</span><span class="p">)</span>
</pre></div></td></tr></table></div>
</div>
</div>
<div class="section" id="EN-US_TOPIC_0000001445186320__section31951421931"><h4 class="sectiontitle">hll_add(hll, hll_hashval)</h4><p id="EN-US_TOPIC_0000001445186320__p219214428317">Description: Adds hll_hashval to an HLL.</p>
<p id="EN-US_TOPIC_0000001445186320__p131929421233">Return type: hll</p>
<p id="EN-US_TOPIC_0000001445186320__p12192194217312">Example:</p>
<div class="codecoloring" codetype="Sql" id="EN-US_TOPIC_0000001445186320__screen101931421639"><div class="highlight"><table class="highlighttable"><tr><td class="linenos"><div class="linenodiv"><pre><span class="normal">1</span>
<span class="normal">2</span>
<span class="normal">3</span>
<span class="normal">4</span>
<span class="normal">5</span></pre></div></td><td class="code"><div><pre><span></span><span class="k">SELECT</span><span class="w"> </span><span class="n">hll_add</span><span class="p">(</span><span class="n">hll_empty</span><span class="p">(),</span><span class="w"> </span><span class="n">hll_hash_integer</span><span class="p">(</span><span class="mi">1</span><span class="p">));</span>
<span class="w"> </span><span class="n">hll_add</span><span class="w"> </span>
<span class="c1">--------------------------</span>
<span class="w"> </span><span class="err">\</span><span class="n">x128b7f8895a3f5af28cafe</span>
<span class="p">(</span><span class="mi">1</span><span class="w"> </span><span class="k">row</span><span class="p">)</span>
</pre></div></td></tr></table></div>
</div>
</div>
<div class="section" id="EN-US_TOPIC_0000001445186320__section17308144520315"><h4 class="sectiontitle">hll_add_rev(hll_hashval, hll)</h4><p id="EN-US_TOPIC_0000001445186320__p183061645631">Description: Adds hll_hashval to an HLL. This function works the same as hll_add, except that the positions of parameters are switched.</p>
<p id="EN-US_TOPIC_0000001445186320__p133063451439">Return type: hll</p>
<p id="EN-US_TOPIC_0000001445186320__p6306204518312">Example:</p>
<div class="codecoloring" codetype="Sql" id="EN-US_TOPIC_0000001445186320__screen1430610451139"><div class="highlight"><table class="highlighttable"><tr><td class="linenos"><div class="linenodiv"><pre><span class="normal">1</span>
<span class="normal">2</span>
<span class="normal">3</span>
<span class="normal">4</span>
<span class="normal">5</span></pre></div></td><td class="code"><div><pre><span></span><span class="k">SELECT</span><span class="w"> </span><span class="n">hll_add_rev</span><span class="p">(</span><span class="n">hll_hash_integer</span><span class="p">(</span><span class="mi">1</span><span class="p">),</span><span class="w"> </span><span class="n">hll_empty</span><span class="p">());</span>
<span class="w"> </span><span class="n">hll_add_rev</span><span class="w"> </span>
<span class="c1">--------------------------</span>
<span class="w"> </span><span class="err">\</span><span class="n">x128b7f8895a3f5af28cafe</span>
<span class="p">(</span><span class="mi">1</span><span class="w"> </span><span class="k">row</span><span class="p">)</span>
</pre></div></td></tr></table></div>
</div>
</div>
<div class="section" id="EN-US_TOPIC_0000001445186320__section932820482312"><h4 class="sectiontitle">hll_eq(hll, hll)</h4><p id="EN-US_TOPIC_0000001445186320__p113264489318">Description: Compares two HLLs to check whether they are the same.</p>
<p id="EN-US_TOPIC_0000001445186320__p10326134815312">Return type: bool</p>
<p id="EN-US_TOPIC_0000001445186320__p12326164819320">Example:</p>
<div class="codecoloring" codetype="Sql" id="EN-US_TOPIC_0000001445186320__screen203269484318"><div class="highlight"><table class="highlighttable"><tr><td class="linenos"><div class="linenodiv"><pre><span class="normal">1</span>
<span class="normal">2</span>
<span class="normal">3</span>
<span class="normal">4</span>
<span class="normal">5</span></pre></div></td><td class="code"><div><pre><span></span><span class="k">SELECT</span><span class="w"> </span><span class="n">hll_eq</span><span class="p">(</span><span class="n">hll_add</span><span class="p">(</span><span class="n">hll_empty</span><span class="p">(),</span><span class="w"> </span><span class="n">hll_hash_integer</span><span class="p">(</span><span class="mi">1</span><span class="p">)),</span><span class="w"> </span><span class="n">hll_add</span><span class="p">(</span><span class="n">hll_empty</span><span class="p">(),</span><span class="w"> </span><span class="n">hll_hash_integer</span><span class="p">(</span><span class="mi">2</span><span class="p">)));</span>
<span class="w"> </span><span class="n">hll_eq</span><span class="w"> </span>
<span class="c1">--------</span>
<span class="w"> </span><span class="n">f</span>
<span class="p">(</span><span class="mi">1</span><span class="w"> </span><span class="k">row</span><span class="p">)</span>
</pre></div></td></tr></table></div>
</div>
</div>
<div class="section" id="EN-US_TOPIC_0000001445186320__section9170451739"><h4 class="sectiontitle">hll_ne(hll, hll)</h4><p id="EN-US_TOPIC_0000001445186320__p2168175115319">Description: Compares two HLLs to check whether they are different.</p>
<p id="EN-US_TOPIC_0000001445186320__p6168125114319">Return type: bool</p>
<p id="EN-US_TOPIC_0000001445186320__p716813516313">Example:</p>
<div class="codecoloring" codetype="Sql" id="EN-US_TOPIC_0000001445186320__screen51699511337"><div class="highlight"><table class="highlighttable"><tr><td class="linenos"><div class="linenodiv"><pre><span class="normal">1</span>
<span class="normal">2</span>
<span class="normal">3</span>
<span class="normal">4</span>
<span class="normal">5</span></pre></div></td><td class="code"><div><pre><span></span><span class="k">SELECT</span><span class="w"> </span><span class="n">hll_ne</span><span class="p">(</span><span class="n">hll_add</span><span class="p">(</span><span class="n">hll_empty</span><span class="p">(),</span><span class="w"> </span><span class="n">hll_hash_integer</span><span class="p">(</span><span class="mi">1</span><span class="p">)),</span><span class="w"> </span><span class="n">hll_add</span><span class="p">(</span><span class="n">hll_empty</span><span class="p">(),</span><span class="w"> </span><span class="n">hll_hash_integer</span><span class="p">(</span><span class="mi">2</span><span class="p">)));</span>
<span class="w"> </span><span class="n">hll_ne</span><span class="w"> </span>
<span class="c1">--------</span>
<span class="w"> </span><span class="n">t</span>
<span class="p">(</span><span class="mi">1</span><span class="w"> </span><span class="k">row</span><span class="p">)</span>
</pre></div></td></tr></table></div>
</div>
</div>
<div class="section" id="EN-US_TOPIC_0000001445186320__section177355417314"><h4 class="sectiontitle">hll_cardinality(hll)</h4><p id="EN-US_TOPIC_0000001445186320__p187013544319">Description: Calculates the number of distinct values of an HLL.</p>
<p id="EN-US_TOPIC_0000001445186320__p97065416312">Return type: integer</p>
<p id="EN-US_TOPIC_0000001445186320__p770175413313">Example:</p>
<div class="codecoloring" codetype="Sql" id="EN-US_TOPIC_0000001445186320__screen137117548318"><div class="highlight"><table class="highlighttable"><tr><td class="linenos"><div class="linenodiv"><pre><span class="normal">1</span>
<span class="normal">2</span>
<span class="normal">3</span>
<span class="normal">4</span>
<span class="normal">5</span></pre></div></td><td class="code"><div><pre><span></span><span class="k">SELECT</span><span class="w"> </span><span class="n">hll_cardinality</span><span class="p">(</span><span class="n">hll_empty</span><span class="p">()</span><span class="w"> </span><span class="o">||</span><span class="w"> </span><span class="n">hll_hash_integer</span><span class="p">(</span><span class="mi">1</span><span class="p">));</span>
<span class="w"> </span><span class="n">hll_cardinality</span><span class="w"> </span>
<span class="c1">-----------------</span>
<span class="w"> </span><span class="mi">1</span>
<span class="p">(</span><span class="mi">1</span><span class="w"> </span><span class="k">row</span><span class="p">)</span>
</pre></div></td></tr></table></div>
</div>
</div>
<div class="section" id="EN-US_TOPIC_0000001445186320__section83523571536"><h4 class="sectiontitle">hll_union(hll, hll)</h4><p id="EN-US_TOPIC_0000001445186320__p33521057634">Description: Performs the <strong id="EN-US_TOPIC_0000001445186320__b110253198594211">UNION</strong> operation on two HLL data structures to obtain one HLL.</p>
<p id="EN-US_TOPIC_0000001445186320__p1035212571038">Return type: hll</p>
<p id="EN-US_TOPIC_0000001445186320__p143521357135">Example:</p>
<div class="codecoloring" codetype="Sql" id="EN-US_TOPIC_0000001445186320__screen53521757937"><div class="highlight"><table class="highlighttable"><tr><td class="linenos"><div class="linenodiv"><pre><span class="normal">1</span>
<span class="normal">2</span>
<span class="normal">3</span>
<span class="normal">4</span>
<span class="normal">5</span></pre></div></td><td class="code"><div><pre><span></span><span class="k">SELECT</span><span class="w"> </span><span class="n">hll_union</span><span class="p">(</span><span class="n">hll_add</span><span class="p">(</span><span class="n">hll_empty</span><span class="p">(),</span><span class="w"> </span><span class="n">hll_hash_integer</span><span class="p">(</span><span class="mi">1</span><span class="p">)),</span><span class="w"> </span><span class="n">hll_add</span><span class="p">(</span><span class="n">hll_empty</span><span class="p">(),</span><span class="w"> </span><span class="n">hll_hash_integer</span><span class="p">(</span><span class="mi">2</span><span class="p">)));</span>
<span class="w"> </span><span class="n">hll_union</span><span class="w"> </span>
<span class="c1">------------------------------------------</span>
<span class="w"> </span><span class="err">\</span><span class="n">x128b7f8895a3f5af28cafeda0ce907e4355b60</span>
<span class="p">(</span><span class="mi">1</span><span class="w"> </span><span class="k">row</span><span class="p">)</span>
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<div class="parentlink"><strong>Parent topic:</strong> <a href="dws_06_0042.html">HLL Functions and Operators</a></div>
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