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<!DOCTYPE html>
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<title>Basic Usage of python-rocksdb — python-rocksdb 0.6.7 documentation</title>
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<div class="section" id="basic-usage-of-python-rocksdb">
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<h1>Basic Usage of python-rocksdb<a class="headerlink" href="#basic-usage-of-python-rocksdb" title="Permalink to this headline">¶</a></h1>
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<div class="section" id="wrtie-batch">
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<h2>Wrtie Batch<a class="headerlink" href="#wrtie-batch" title="Permalink to this headline">¶</a></h2>
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<p>It is also possible to gather modifications and
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apply them in a single operation</p>
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<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">update</span> <span class="o">=</span> <span class="n">pyrocksdb</span><span class="o">.</span><span class="n">WriteBatch</span><span class="p">()</span>
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<span class="c1"># collect the operations</span>
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<span class="n">update</span><span class="o">.</span><span class="n">put</span><span class="p">(</span><span class="s1">'key1'</span><span class="p">,</span> <span class="s1">'value1'</span><span class="p">)</span>
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<span class="n">update</span><span class="o">.</span><span class="n">put</span><span class="p">(</span><span class="s1">'key2'</span><span class="p">,</span> <span class="s1">'value2'</span><span class="p">)</span>
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<span class="n">update</span><span class="o">.</span><span class="n">delete</span><span class="p">(</span><span class="s1">'key1'</span><span class="p">)</span>
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<span class="n">opts</span> <span class="o">=</span> <span class="n">pyrocksdb</span><span class="o">.</span><span class="n">WriteOptions</span><span class="p">()</span>
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<span class="c1"># Apply these operatios in a single operation</span>
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<span class="n">s</span> <span class="o">=</span> <span class="n">db</span><span class="o">.</span><span class="n">write</span><span class="p">(</span><span class="n">opts</span><span class="p">,</span> <span class="n">update</span><span class="p">)</span>
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<span class="k">assert</span> <span class="n">s</span><span class="o">.</span><span class="n">ok</span><span class="p">()</span>
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<span class="n">opts</span> <span class="o">=</span> <span class="n">pyrocksdb</span><span class="o">.</span><span class="n">ReadOptions</span><span class="p">()</span>
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<span class="n">blob</span> <span class="o">=</span> <span class="n">db</span><span class="o">.</span><span class="n">get</span><span class="p">(</span><span class="n">opts</span><span class="p">,</span> <span class="s1">'key1'</span><span class="p">)</span>
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<span class="k">assert</span> <span class="n">blob</span><span class="o">.</span><span class="n">status</span><span class="o">.</span><span class="n">is_not_found</span><span class="p">()</span>
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<span class="n">blob</span> <span class="o">=</span> <span class="n">db</span><span class="o">.</span><span class="n">get</span><span class="p">(</span><span class="n">opts</span><span class="p">,</span> <span class="s1">'key2'</span><span class="p">)</span>
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<span class="k">assert</span> <span class="n">blob</span><span class="o">.</span><span class="n">status</span><span class="o">.</span><span class="n">ok</span><span class="p">()</span>
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<span class="k">assert</span> <span class="n">blob</span><span class="o">.</span><span class="n">data</span> <span class="o">==</span> <span class="s1">'value2'</span>
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<span class="n">db</span><span class="o">.</span><span class="n">close</span><span class="p">()</span>
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</pre></div>
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</div>
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</div>
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<div class="section" id="iteration">
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<h2>Iteration<a class="headerlink" href="#iteration" title="Permalink to this headline">¶</a></h2>
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<p>Iterators behave slightly different than expected. Per default they are not
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valid. So you have to call one of its seek methods first</p>
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<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">opts</span> <span class="o">=</span> <span class="n">pyrocksdb</span><span class="o">.</span><span class="n">WriteOptions</span><span class="p">()</span>
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<span class="n">s</span> <span class="o">=</span> <span class="p">{</span><span class="s1">'key1'</span><span class="p">:</span> <span class="s1">'value1'</span><span class="p">,</span> <span class="s1">'key2'</span><span class="p">:</span> <span class="s1">'value2'</span><span class="p">,</span> <span class="s1">'key3'</span><span class="p">:</span> <span class="s1">'value3'</span><span class="p">}</span>
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<span class="k">for</span> <span class="n">k</span><span class="p">,</span> <span class="n">v</span> <span class="ow">in</span> <span class="n">s</span><span class="o">.</span><span class="n">items</span><span class="p">():</span>
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<span class="n">db</span><span class="o">.</span><span class="n">put</span><span class="p">(</span><span class="n">opts</span><span class="p">,</span> <span class="n">k</span><span class="p">,</span> <span class="n">v</span><span class="p">)</span>
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<span class="n">opts</span> <span class="o">=</span> <span class="n">pyrocksdb</span><span class="o">.</span><span class="n">ReadOptions</span><span class="p">()</span>
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<span class="n">it</span> <span class="o">=</span> <span class="n">db</span><span class="o">.</span><span class="n">iterator</span><span class="p">(</span><span class="n">opts</span><span class="p">)</span>
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<span class="c1"># call this first</span>
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<span class="n">it</span><span class="o">.</span><span class="n">seek_to_first</span><span class="p">()</span>
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<span class="k">assert</span> <span class="n">it</span><span class="o">.</span><span class="n">status</span><span class="p">()</span><span class="o">.</span><span class="n">ok</span><span class="p">()</span>
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<span class="k">assert</span> <span class="n">it</span><span class="o">.</span><span class="n">valid</span><span class="p">()</span>
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<span class="k">for</span> <span class="n">k</span><span class="p">,</span> <span class="n">v</span> <span class="ow">in</span> <span class="n">s</span><span class="o">.</span><span class="n">items</span><span class="p">():</span>
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<span class="k">assert</span> <span class="n">it</span><span class="o">.</span><span class="n">key</span><span class="p">()</span><span class="o">.</span><span class="n">data</span><span class="p">()</span> <span class="o">==</span> <span class="n">k</span>
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<span class="k">assert</span> <span class="n">it</span><span class="o">.</span><span class="n">value</span><span class="p">()</span><span class="o">.</span><span class="n">data</span><span class="p">()</span> <span class="o">==</span> <span class="n">v</span>
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<span class="n">it</span><span class="o">.</span><span class="n">next</span><span class="p">()</span>
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<span class="k">assert</span> <span class="ow">not</span> <span class="n">it</span><span class="o">.</span><span class="n">valid</span><span class="p">()</span>
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<span class="n">it</span><span class="o">.</span><span class="n">seek</span><span class="p">(</span><span class="s1">'key1'</span><span class="p">)</span>
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<span class="k">assert</span> <span class="n">it</span><span class="o">.</span><span class="n">valid</span><span class="p">()</span>
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<span class="k">assert</span> <span class="n">it</span><span class="o">.</span><span class="n">key</span><span class="p">()</span><span class="o">.</span><span class="n">data</span><span class="p">()</span> <span class="o">==</span> <span class="s1">'key1'</span>
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<span class="k">assert</span> <span class="n">it</span><span class="o">.</span><span class="n">value</span><span class="p">()</span><span class="o">.</span><span class="n">data</span><span class="p">()</span> <span class="o">==</span> <span class="s1">'value1'</span>
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<span class="n">it</span><span class="o">.</span><span class="n">seek</span><span class="p">(</span><span class="s1">'key2'</span><span class="p">)</span>
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<span class="k">assert</span> <span class="n">it</span><span class="o">.</span><span class="n">valid</span><span class="p">()</span>
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<span class="k">assert</span> <span class="n">it</span><span class="o">.</span><span class="n">key</span><span class="p">()</span><span class="o">.</span><span class="n">data</span><span class="p">()</span> <span class="o">==</span> <span class="s1">'key2'</span>
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<span class="k">assert</span> <span class="n">it</span><span class="o">.</span><span class="n">value</span><span class="p">()</span><span class="o">.</span><span class="n">data</span><span class="p">()</span> <span class="o">==</span> <span class="s1">'value2'</span>
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<span class="n">it</span><span class="o">.</span><span class="n">seek</span><span class="p">(</span><span class="s1">'key4'</span><span class="p">)</span>
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<span class="k">assert</span> <span class="ow">not</span> <span class="n">it</span><span class="o">.</span><span class="n">valid</span><span class="p">()</span>
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<span class="n">it</span><span class="o">.</span><span class="n">seek_for_prev</span><span class="p">(</span><span class="s1">'key0'</span><span class="p">)</span>
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<span class="k">assert</span> <span class="ow">not</span> <span class="n">it</span><span class="o">.</span><span class="n">valid</span><span class="p">()</span>
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<span class="n">it</span><span class="o">.</span><span class="n">seek_for_prev</span><span class="p">(</span><span class="s1">'key4'</span><span class="p">)</span>
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<span class="k">assert</span> <span class="n">it</span><span class="o">.</span><span class="n">valid</span><span class="p">()</span>
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</pre></div>
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