This file is indexed.

/usr/share/doc/python3-postgresql/html/_modules/postgresql/alock.html is in python3-postgresql 1.1.0-1build1.

This file is owned by root:root, with mode 0o644.

The actual contents of the file can be viewed below.

  1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
  "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">


<html xmlns="http://www.w3.org/1999/xhtml">
  <head>
    <meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
    
    <title>postgresql.alock &mdash; py-postgresql 1.1.0 documentation</title>
    
    <link rel="stylesheet" href="../../_static/default.css" type="text/css" />
    <link rel="stylesheet" href="../../_static/pygments.css" type="text/css" />
    
    <script type="text/javascript">
      var DOCUMENTATION_OPTIONS = {
        URL_ROOT:    '../../',
        VERSION:     '1.1.0',
        COLLAPSE_INDEX: false,
        FILE_SUFFIX: '.html',
        HAS_SOURCE:  true
      };
    </script>
    <script type="text/javascript" src="../../_static/jquery.js"></script>
    <script type="text/javascript" src="../../_static/underscore.js"></script>
    <script type="text/javascript" src="../../_static/doctools.js"></script>
    <link rel="top" title="py-postgresql 1.1.0 documentation" href="../../index.html" />
    <link rel="up" title="postgresql" href="../postgresql.html" />
 
<link rel="stylesheet" href="_static/unsuck.css" type="text/css" />

  </head>
  <body>
    <div class="related">
      <h3>Navigation</h3>
      <ul>
        <li class="right" style="margin-right: 10px">
          <a href="../../genindex.html" title="General Index"
             accesskey="I">index</a></li>
        <li class="right" >
          <a href="../../py-modindex.html" title="Python Module Index"
             >modules</a> |</li>
        <li><a href="../../index.html">py-postgresql 1.1.0 documentation</a> &raquo;</li>
          <li><a href="../index.html" >Module code</a> &raquo;</li>
          <li><a href="../postgresql.html" accesskey="U">postgresql</a> &raquo;</li> 
      </ul>
    </div>  

    <div class="document">
      <div class="documentwrapper">
        <div class="bodywrapper">
          <div class="body">
            
  <h1>Source code for postgresql.alock</h1><div class="highlight"><pre>
<span class="c">##</span>
<span class="c"># .alock - Advisory Locks</span>
<span class="c">##</span>
<span class="sd">&quot;&quot;&quot;</span>
<span class="sd">Tools for Advisory Locks</span>
<span class="sd">&quot;&quot;&quot;</span>
<span class="kn">from</span> <span class="nn">abc</span> <span class="kn">import</span> <span class="n">abstractmethod</span><span class="p">,</span> <span class="n">abstractproperty</span>
<span class="kn">from</span> <span class="nn">.python.element</span> <span class="kn">import</span> <span class="n">Element</span>

<span class="n">__all__</span> <span class="o">=</span> <span class="p">[</span>
	<span class="s">&#39;ALock&#39;</span><span class="p">,</span>
	<span class="s">&#39;ExclusiveLock&#39;</span><span class="p">,</span>
	<span class="s">&#39;ShareLock&#39;</span><span class="p">,</span>
<span class="p">]</span>

<div class="viewcode-block" id="ALock"><a class="viewcode-back" href="../../reference.html#postgresql.alock.ALock">[docs]</a><span class="k">class</span> <span class="nc">ALock</span><span class="p">(</span><span class="n">Element</span><span class="p">):</span>
	<span class="sd">&quot;&quot;&quot;</span>
<span class="sd">	Advisory Lock class for managing the acquisition and release of a sequence</span>
<span class="sd">	of PostgreSQL advisory locks.</span>

<span class="sd">	ALock()&#39;s are fairly consistent with threading.RLock()&#39;s. They can be</span>
<span class="sd">	acquired multiple times, and they must be released the same number of times</span>
<span class="sd">	for the lock to actually be released.</span>

<span class="sd">	A notably difference is that ALock&#39;s manage a sequence of lock identifiers.</span>
<span class="sd">	This means that a given ALock() may represent multiple advisory locks.</span>
<span class="sd">	&quot;&quot;&quot;</span>
	<span class="n">_e_factors</span> <span class="o">=</span> <span class="p">(</span><span class="s">&#39;database&#39;</span><span class="p">,</span> <span class="s">&#39;identifiers&#39;</span><span class="p">,)</span>
	<span class="n">_e_label</span> <span class="o">=</span> <span class="s">&#39;ALOCK&#39;</span>
	<span class="k">def</span> <span class="nf">_e_metas</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span>
		<span class="n">headfmt</span> <span class="o">=</span> <span class="s">&quot;{1} [{0}]&quot;</span><span class="o">.</span><span class="n">format</span>
	<span class="p">):</span>
		<span class="k">yield</span> <span class="bp">None</span><span class="p">,</span> <span class="n">headfmt</span><span class="p">(</span><span class="bp">self</span><span class="o">.</span><span class="n">state</span><span class="p">,</span> <span class="bp">self</span><span class="o">.</span><span class="n">mode</span><span class="p">)</span>

	<span class="nd">@abstractproperty</span>
<div class="viewcode-block" id="ALock.mode"><a class="viewcode-back" href="../../reference.html#postgresql.alock.ALock.mode">[docs]</a>	<span class="k">def</span> <span class="nf">mode</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
		<span class="sd">&quot;&quot;&quot;</span>
<span class="sd">		The mode of the lock class.</span>
<span class="sd">		&quot;&quot;&quot;</span>
</div>
	<span class="nd">@abstractproperty</span>
	<span class="k">def</span> <span class="nf">__select_statements__</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
		<span class="sd">&quot;&quot;&quot;</span>
<span class="sd">		Implemented by subclasses to return the statements to try, acquire, and</span>
<span class="sd">		release the advisory lock.</span>

<span class="sd">		Returns a triple of callables where each callable takes two arguments,</span>
<span class="sd">		the lock-id pairs, and then the int8 lock-ids.</span>
<span class="sd">		``(try, acquire, release)``.</span>
<span class="sd">		&quot;&quot;&quot;</span>

	<span class="nd">@staticmethod</span>
	<span class="k">def</span> <span class="nf">_split_lock_identifiers</span><span class="p">(</span><span class="n">idseq</span><span class="p">):</span>
		<span class="c"># lame O(2)</span>
		<span class="n">id_pairs</span> <span class="o">=</span> <span class="p">[</span>
			<span class="nb">list</span><span class="p">(</span><span class="n">x</span><span class="p">)</span> <span class="k">if</span> <span class="n">x</span><span class="o">.</span><span class="n">__class__</span> <span class="ow">is</span> <span class="ow">not</span> <span class="nb">int</span> <span class="k">else</span> <span class="p">[</span><span class="bp">None</span><span class="p">,</span><span class="bp">None</span><span class="p">]</span>
			<span class="k">for</span> <span class="n">x</span> <span class="ow">in</span> <span class="n">idseq</span>
		<span class="p">]</span>
		<span class="n">ids</span> <span class="o">=</span> <span class="p">[</span>
			<span class="n">x</span> <span class="k">if</span> <span class="n">x</span><span class="o">.</span><span class="n">__class__</span> <span class="ow">is</span> <span class="nb">int</span> <span class="k">else</span> <span class="bp">None</span>
			<span class="k">for</span> <span class="n">x</span> <span class="ow">in</span> <span class="n">idseq</span>
		<span class="p">]</span>
		<span class="k">return</span> <span class="p">(</span><span class="n">id_pairs</span><span class="p">,</span> <span class="n">ids</span><span class="p">)</span>

<div class="viewcode-block" id="ALock.acquire"><a class="viewcode-back" href="../../reference.html#postgresql.alock.ALock.acquire">[docs]</a>	<span class="k">def</span> <span class="nf">acquire</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">blocking</span> <span class="o">=</span> <span class="bp">True</span><span class="p">,</span> <span class="nb">len</span> <span class="o">=</span> <span class="nb">len</span><span class="p">):</span>
		<span class="sd">&quot;&quot;&quot;</span>
<span class="sd">		Acquire the locks using the configured identifiers.</span>
<span class="sd">		&quot;&quot;&quot;</span>
		<span class="k">if</span> <span class="bp">self</span><span class="o">.</span><span class="n">_count</span> <span class="o">==</span> <span class="mi">0</span><span class="p">:</span>
			<span class="c"># _count is zero, so the locks need to be acquired.</span>
			<span class="n">wait</span> <span class="o">=</span> <span class="nb">bool</span><span class="p">(</span><span class="n">blocking</span><span class="p">)</span>
			<span class="k">if</span> <span class="n">wait</span><span class="p">:</span>
				<span class="bp">self</span><span class="o">.</span><span class="n">_acquire</span><span class="p">(</span><span class="bp">self</span><span class="o">.</span><span class="n">_id_pairs</span><span class="p">,</span> <span class="bp">self</span><span class="o">.</span><span class="n">_ids</span><span class="p">)</span>
			<span class="k">else</span><span class="p">:</span>
				<span class="c"># grab the success of each lock id. if some were</span>
				<span class="c"># unsuccessful, then the ones that were successful need to be</span>
				<span class="c"># released.</span>
				<span class="n">r</span> <span class="o">=</span> <span class="bp">self</span><span class="o">.</span><span class="n">_try</span><span class="p">(</span><span class="bp">self</span><span class="o">.</span><span class="n">_id_pairs</span><span class="p">,</span> <span class="bp">self</span><span class="o">.</span><span class="n">_ids</span><span class="p">)</span>
				<span class="c"># accumulate the identifiers that *did* lock</span>
				<span class="n">release_seq</span> <span class="o">=</span> <span class="p">[</span>
					<span class="nb">id</span> <span class="k">for</span> <span class="n">didlock</span><span class="p">,</span> <span class="nb">id</span> <span class="ow">in</span> <span class="nb">zip</span><span class="p">(</span><span class="n">r</span><span class="p">,</span> <span class="bp">self</span><span class="o">.</span><span class="n">identifiers</span><span class="p">)</span> <span class="k">if</span> <span class="n">didlock</span><span class="p">[</span><span class="mi">0</span><span class="p">]</span>
				<span class="p">]</span>
				<span class="k">if</span> <span class="nb">len</span><span class="p">(</span><span class="n">release_seq</span><span class="p">)</span> <span class="o">!=</span> <span class="nb">len</span><span class="p">(</span><span class="bp">self</span><span class="o">.</span><span class="n">identifiers</span><span class="p">):</span>
					<span class="c"># some failed, so release the acquired and return False</span>
					<span class="c">#</span>
					<span class="c"># reverse in case there is another waiting for all.</span>
					<span class="c"># that is, release last-to-first so that if another is waiting</span>
					<span class="c"># on the same seq that it should be able to acquire all of</span>
					<span class="c"># them once the contended lock is released.</span>
					<span class="n">release_seq</span><span class="o">.</span><span class="n">reverse</span><span class="p">()</span>
					<span class="bp">self</span><span class="o">.</span><span class="n">_release</span><span class="p">(</span><span class="o">*</span><span class="bp">self</span><span class="o">.</span><span class="n">_split_lock_identifiers</span><span class="p">(</span><span class="n">release_seq</span><span class="p">))</span>
					<span class="c"># unable to acquire all.</span>
					<span class="k">return</span> <span class="bp">False</span>
		<span class="bp">self</span><span class="o">.</span><span class="n">_count</span> <span class="o">=</span> <span class="bp">self</span><span class="o">.</span><span class="n">_count</span> <span class="o">+</span> <span class="mi">1</span>
		<span class="k">return</span> <span class="bp">True</span>
</div>
	<span class="k">def</span> <span class="nf">__enter__</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
		<span class="bp">self</span><span class="o">.</span><span class="n">acquire</span><span class="p">()</span>
		<span class="k">return</span> <span class="bp">self</span>

<div class="viewcode-block" id="ALock.release"><a class="viewcode-back" href="../../reference.html#postgresql.alock.ALock.release">[docs]</a>	<span class="k">def</span> <span class="nf">release</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
		<span class="sd">&quot;&quot;&quot;</span>
<span class="sd">		Release the locks using the configured identifiers.</span>
<span class="sd">		&quot;&quot;&quot;</span>
		<span class="k">if</span> <span class="bp">self</span><span class="o">.</span><span class="n">_count</span> <span class="o">&lt;</span> <span class="mi">1</span><span class="p">:</span>
			<span class="k">raise</span> <span class="ne">RuntimeError</span><span class="p">(</span><span class="s">&quot;cannot release un-acquired lock&quot;</span><span class="p">)</span>
		<span class="k">if</span> <span class="ow">not</span> <span class="bp">self</span><span class="o">.</span><span class="n">database</span><span class="o">.</span><span class="n">closed</span> <span class="ow">and</span> <span class="bp">self</span><span class="o">.</span><span class="n">_count</span> <span class="o">&gt;</span> <span class="mi">0</span><span class="p">:</span>
			<span class="c"># if the database has been closed, or the count will</span>
			<span class="c"># remain non-zero, there is no need to release.</span>
			<span class="bp">self</span><span class="o">.</span><span class="n">_release</span><span class="p">(</span><span class="nb">reversed</span><span class="p">(</span><span class="bp">self</span><span class="o">.</span><span class="n">_id_pairs</span><span class="p">),</span> <span class="nb">reversed</span><span class="p">(</span><span class="bp">self</span><span class="o">.</span><span class="n">_ids</span><span class="p">))</span>
			<span class="c"># decrement the count nonetheless.</span>
		<span class="bp">self</span><span class="o">.</span><span class="n">_count</span> <span class="o">=</span> <span class="bp">self</span><span class="o">.</span><span class="n">_count</span> <span class="o">-</span> <span class="mi">1</span>
</div>
	<span class="k">def</span> <span class="nf">__exit__</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">typ</span><span class="p">,</span> <span class="n">val</span><span class="p">,</span> <span class="n">tb</span><span class="p">):</span>
		<span class="bp">self</span><span class="o">.</span><span class="n">release</span><span class="p">()</span>

<div class="viewcode-block" id="ALock.locked"><a class="viewcode-back" href="../../reference.html#postgresql.alock.ALock.locked">[docs]</a>	<span class="k">def</span> <span class="nf">locked</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
		<span class="sd">&quot;&quot;&quot;</span>
<span class="sd">		Whether the locks have been acquired. This method is sensitive to the</span>
<span class="sd">		connection&#39;s state. If the connection is closed, it will return False.</span>
<span class="sd">		&quot;&quot;&quot;</span>
		<span class="k">return</span> <span class="p">(</span><span class="bp">self</span><span class="o">.</span><span class="n">_count</span> <span class="o">&gt;</span> <span class="mi">0</span><span class="p">)</span> <span class="ow">and</span> <span class="p">(</span><span class="ow">not</span> <span class="bp">self</span><span class="o">.</span><span class="n">database</span><span class="o">.</span><span class="n">closed</span><span class="p">)</span>
</div>
	<span class="nd">@property</span>
	<span class="k">def</span> <span class="nf">state</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
		<span class="k">return</span> <span class="s">&#39;locked&#39;</span> <span class="k">if</span> <span class="bp">self</span><span class="o">.</span><span class="n">locked</span><span class="p">()</span> <span class="k">else</span> <span class="s">&#39;unlocked&#39;</span>

	<span class="k">def</span> <span class="nf">__init__</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">database</span><span class="p">,</span> <span class="o">*</span><span class="n">identifiers</span><span class="p">):</span>
		<span class="sd">&quot;&quot;&quot;</span>
<span class="sd">		Initialize the lock object to manage a sequence of advisory locks</span>
<span class="sd">		for use with the given database.</span>
<span class="sd">		&quot;&quot;&quot;</span>
		<span class="bp">self</span><span class="o">.</span><span class="n">_count</span> <span class="o">=</span> <span class="mi">0</span>
		<span class="bp">self</span><span class="o">.</span><span class="n">connection</span> <span class="o">=</span> <span class="bp">self</span><span class="o">.</span><span class="n">database</span> <span class="o">=</span> <span class="n">database</span>
		<span class="bp">self</span><span class="o">.</span><span class="n">identifiers</span> <span class="o">=</span> <span class="n">identifiers</span>
		<span class="bp">self</span><span class="o">.</span><span class="n">_id_pairs</span><span class="p">,</span> <span class="bp">self</span><span class="o">.</span><span class="n">_ids</span> <span class="o">=</span> <span class="bp">self</span><span class="o">.</span><span class="n">_split_lock_identifiers</span><span class="p">(</span><span class="n">identifiers</span><span class="p">)</span>
		<span class="bp">self</span><span class="o">.</span><span class="n">_try</span><span class="p">,</span> <span class="bp">self</span><span class="o">.</span><span class="n">_acquire</span><span class="p">,</span> <span class="bp">self</span><span class="o">.</span><span class="n">_release</span> <span class="o">=</span> <span class="bp">self</span><span class="o">.</span><span class="n">__select_statements__</span><span class="p">()</span>
</div>
<span class="k">class</span> <span class="nc">ShareLock</span><span class="p">(</span><span class="n">ALock</span><span class="p">):</span>
	<span class="n">mode</span> <span class="o">=</span> <span class="s">&#39;share&#39;</span>

	<span class="k">def</span> <span class="nf">__select_statements__</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
		<span class="k">return</span> <span class="p">(</span>
			<span class="bp">self</span><span class="o">.</span><span class="n">database</span><span class="o">.</span><span class="n">sys</span><span class="o">.</span><span class="n">try_advisory_shared</span><span class="p">,</span>
			<span class="bp">self</span><span class="o">.</span><span class="n">database</span><span class="o">.</span><span class="n">sys</span><span class="o">.</span><span class="n">acquire_advisory_shared</span><span class="p">,</span>
			<span class="bp">self</span><span class="o">.</span><span class="n">database</span><span class="o">.</span><span class="n">sys</span><span class="o">.</span><span class="n">release_advisory_shared</span><span class="p">,</span>
		<span class="p">)</span>

<span class="k">class</span> <span class="nc">ExclusiveLock</span><span class="p">(</span><span class="n">ALock</span><span class="p">):</span>
	<span class="n">mode</span> <span class="o">=</span> <span class="s">&#39;exclusive&#39;</span>

	<span class="k">def</span> <span class="nf">__select_statements__</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
		<span class="k">return</span> <span class="p">(</span>
			<span class="bp">self</span><span class="o">.</span><span class="n">database</span><span class="o">.</span><span class="n">sys</span><span class="o">.</span><span class="n">try_advisory_exclusive</span><span class="p">,</span>
			<span class="bp">self</span><span class="o">.</span><span class="n">database</span><span class="o">.</span><span class="n">sys</span><span class="o">.</span><span class="n">acquire_advisory_exclusive</span><span class="p">,</span>
			<span class="bp">self</span><span class="o">.</span><span class="n">database</span><span class="o">.</span><span class="n">sys</span><span class="o">.</span><span class="n">release_advisory_exclusive</span><span class="p">,</span>
		<span class="p">)</span>
</pre></div>

          </div>
        </div>
      </div>
      <div class="sphinxsidebar">
        <div class="sphinxsidebarwrapper">
<div id="searchbox" style="display: none">
  <h3>Quick search</h3>
    <form class="search" action="../../search.html" method="get">
      <input type="text" name="q" />
      <input type="submit" value="Go" />
      <input type="hidden" name="check_keywords" value="yes" />
      <input type="hidden" name="area" value="default" />
    </form>
    <p class="searchtip" style="font-size: 90%">
    Enter search terms or a module, class or function name.
    </p>
</div>
<script type="text/javascript">$('#searchbox').show(0);</script>
        </div>
      </div>
      <div class="clearer"></div>
    </div>
    <div class="related">
      <h3>Navigation</h3>
      <ul>
        <li class="right" style="margin-right: 10px">
          <a href="../../genindex.html" title="General Index"
             >index</a></li>
        <li class="right" >
          <a href="../../py-modindex.html" title="Python Module Index"
             >modules</a> |</li>
        <li><a href="../../index.html">py-postgresql 1.1.0 documentation</a> &raquo;</li>
          <li><a href="../index.html" >Module code</a> &raquo;</li>
          <li><a href="../postgresql.html" >postgresql</a> &raquo;</li> 
      </ul>
    </div>
    <div class="footer">
        &copy; Copyright Python+Postgres.
      Last updated on Mar 31, 2014.
      Created using <a href="http://sphinx-doc.org/">Sphinx</a> 1.2.2.
    </div>
  </body>
</html>