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<title>sqlglot.optimizer.eliminate_subqueries API documentation</title>
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<a href="./../../sqlglot.html">sqlglot</a><wbr>.<a href="./../optimizer.html">optimizer</a><wbr>.eliminate_subqueries </h1>
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<div class="pdoc-code codehilite"><pre><span></span><span id="L-1"><a href="#L-1"><span class="linenos"> 1</span></a><span class="kn">import</span> <span class="nn">itertools</span>
</span><span id="L-2"><a href="#L-2"><span class="linenos"> 2</span></a>
</span><span id="L-3"><a href="#L-3"><span class="linenos"> 3</span></a><span class="kn">from</span> <span class="nn">sqlglot</span> <span class="kn">import</span> <span class="n">expressions</span> <span class="k">as</span> <span class="n">exp</span>
</span><span id="L-4"><a href="#L-4"><span class="linenos"> 4</span></a><span class="kn">from</span> <span class="nn">sqlglot.helper</span> <span class="kn">import</span> <span class="n">find_new_name</span>
</span><span id="L-5"><a href="#L-5"><span class="linenos"> 5</span></a><span class="kn">from</span> <span class="nn">sqlglot.optimizer.scope</span> <span class="kn">import</span> <span class="n">build_scope</span>
</span><span id="L-6"><a href="#L-6"><span class="linenos"> 6</span></a>
</span><span id="L-7"><a href="#L-7"><span class="linenos"> 7</span></a>
</span><span id="L-8"><a href="#L-8"><span class="linenos"> 8</span></a><span class="k">def</span> <span class="nf">eliminate_subqueries</span><span class="p">(</span><span class="n">expression</span><span class="p">):</span>
</span><span id="L-9"><a href="#L-9"><span class="linenos"> 9</span></a><span class="w"> </span><span class="sd">"""</span>
</span><span id="L-10"><a href="#L-10"><span class="linenos"> 10</span></a><span class="sd"> Rewrite derived tables as CTES, deduplicating if possible.</span>
</span><span id="L-11"><a href="#L-11"><span class="linenos"> 11</span></a>
</span><span id="L-12"><a href="#L-12"><span class="linenos"> 12</span></a><span class="sd"> Example:</span>
</span><span id="L-13"><a href="#L-13"><span class="linenos"> 13</span></a><span class="sd"> >>> import sqlglot</span>
</span><span id="L-14"><a href="#L-14"><span class="linenos"> 14</span></a><span class="sd"> >>> expression = sqlglot.parse_one("SELECT a FROM (SELECT * FROM x) AS y")</span>
</span><span id="L-15"><a href="#L-15"><span class="linenos"> 15</span></a><span class="sd"> >>> eliminate_subqueries(expression).sql()</span>
</span><span id="L-16"><a href="#L-16"><span class="linenos"> 16</span></a><span class="sd"> 'WITH y AS (SELECT * FROM x) SELECT a FROM y AS y'</span>
</span><span id="L-17"><a href="#L-17"><span class="linenos"> 17</span></a>
</span><span id="L-18"><a href="#L-18"><span class="linenos"> 18</span></a><span class="sd"> This also deduplicates common subqueries:</span>
</span><span id="L-19"><a href="#L-19"><span class="linenos"> 19</span></a><span class="sd"> >>> expression = sqlglot.parse_one("SELECT a FROM (SELECT * FROM x) AS y CROSS JOIN (SELECT * FROM x) AS z")</span>
</span><span id="L-20"><a href="#L-20"><span class="linenos"> 20</span></a><span class="sd"> >>> eliminate_subqueries(expression).sql()</span>
</span><span id="L-21"><a href="#L-21"><span class="linenos"> 21</span></a><span class="sd"> 'WITH y AS (SELECT * FROM x) SELECT a FROM y AS y CROSS JOIN y AS z'</span>
</span><span id="L-22"><a href="#L-22"><span class="linenos"> 22</span></a>
</span><span id="L-23"><a href="#L-23"><span class="linenos"> 23</span></a><span class="sd"> Args:</span>
</span><span id="L-24"><a href="#L-24"><span class="linenos"> 24</span></a><span class="sd"> expression (sqlglot.Expression): expression</span>
</span><span id="L-25"><a href="#L-25"><span class="linenos"> 25</span></a><span class="sd"> Returns:</span>
</span><span id="L-26"><a href="#L-26"><span class="linenos"> 26</span></a><span class="sd"> sqlglot.Expression: expression</span>
</span><span id="L-27"><a href="#L-27"><span class="linenos"> 27</span></a><span class="sd"> """</span>
</span><span id="L-28"><a href="#L-28"><span class="linenos"> 28</span></a> <span class="k">if</span> <span class="nb">isinstance</span><span class="p">(</span><span class="n">expression</span><span class="p">,</span> <span class="n">exp</span><span class="o">.</span><span class="n">Subquery</span><span class="p">):</span>
</span><span id="L-29"><a href="#L-29"><span class="linenos"> 29</span></a> <span class="c1"># It's possible to have subqueries at the root, e.g. (SELECT * FROM x) LIMIT 1</span>
</span><span id="L-30"><a href="#L-30"><span class="linenos"> 30</span></a> <span class="n">eliminate_subqueries</span><span class="p">(</span><span class="n">expression</span><span class="o">.</span><span class="n">this</span><span class="p">)</span>
</span><span id="L-31"><a href="#L-31"><span class="linenos"> 31</span></a> <span class="k">return</span> <span class="n">expression</span>
</span><span id="L-32"><a href="#L-32"><span class="linenos"> 32</span></a>
</span><span id="L-33"><a href="#L-33"><span class="linenos"> 33</span></a> <span class="n">root</span> <span class="o">=</span> <span class="n">build_scope</span><span class="p">(</span><span class="n">expression</span><span class="p">)</span>
</span><span id="L-34"><a href="#L-34"><span class="linenos"> 34</span></a>
</span><span id="L-35"><a href="#L-35"><span class="linenos"> 35</span></a> <span class="k">if</span> <span class="ow">not</span> <span class="n">root</span><span class="p">:</span>
</span><span id="L-36"><a href="#L-36"><span class="linenos"> 36</span></a> <span class="k">return</span> <span class="n">expression</span>
</span><span id="L-37"><a href="#L-37"><span class="linenos"> 37</span></a>
</span><span id="L-38"><a href="#L-38"><span class="linenos"> 38</span></a> <span class="c1"># Map of alias->Scope|Table</span>
</span><span id="L-39"><a href="#L-39"><span class="linenos"> 39</span></a> <span class="c1"># These are all aliases that are already used in the expression.</span>
</span><span id="L-40"><a href="#L-40"><span class="linenos"> 40</span></a> <span class="c1"># We don't want to create new CTEs that conflict with these names.</span>
</span><span id="L-41"><a href="#L-41"><span class="linenos"> 41</span></a> <span class="n">taken</span> <span class="o">=</span> <span class="p">{}</span>
</span><span id="L-42"><a href="#L-42"><span class="linenos"> 42</span></a>
</span><span id="L-43"><a href="#L-43"><span class="linenos"> 43</span></a> <span class="c1"># All CTE aliases in the root scope are taken</span>
</span><span id="L-44"><a href="#L-44"><span class="linenos"> 44</span></a> <span class="k">for</span> <span class="n">scope</span> <span class="ow">in</span> <span class="n">root</span><span class="o">.</span><span class="n">cte_scopes</span><span class="p">:</span>
</span><span id="L-45"><a href="#L-45"><span class="linenos"> 45</span></a> <span class="n">taken</span><span class="p">[</span><span class="n">scope</span><span class="o">.</span><span class="n">expression</span><span class="o">.</span><span class="n">parent</span><span class="o">.</span><span class="n">alias</span><span class="p">]</span> <span class="o">=</span> <span class="n">scope</span>
</span><span id="L-46"><a href="#L-46"><span class="linenos"> 46</span></a>
</span><span id="L-47"><a href="#L-47"><span class="linenos"> 47</span></a> <span class="c1"># All table names are taken</span>
</span><span id="L-48"><a href="#L-48"><span class="linenos"> 48</span></a> <span class="k">for</span> <span class="n">scope</span> <span class="ow">in</span> <span class="n">root</span><span class="o">.</span><span class="n">traverse</span><span class="p">():</span>
</span><span id="L-49"><a href="#L-49"><span class="linenos"> 49</span></a> <span class="n">taken</span><span class="o">.</span><span class="n">update</span><span class="p">(</span>
</span><span id="L-50"><a href="#L-50"><span class="linenos"> 50</span></a> <span class="p">{</span>
</span><span id="L-51"><a href="#L-51"><span class="linenos"> 51</span></a> <span class="n">source</span><span class="o">.</span><span class="n">name</span><span class="p">:</span> <span class="n">source</span>
</span><span id="L-52"><a href="#L-52"><span class="linenos"> 52</span></a> <span class="k">for</span> <span class="n">_</span><span class="p">,</span> <span class="n">source</span> <span class="ow">in</span> <span class="n">scope</span><span class="o">.</span><span class="n">sources</span><span class="o">.</span><span class="n">items</span><span class="p">()</span>
</span><span id="L-53"><a href="#L-53"><span class="linenos"> 53</span></a> <span class="k">if</span> <span class="nb">isinstance</span><span class="p">(</span><span class="n">source</span><span class="p">,</span> <span class="n">exp</span><span class="o">.</span><span class="n">Table</span><span class="p">)</span>
</span><span id="L-54"><a href="#L-54"><span class="linenos"> 54</span></a> <span class="p">}</span>
</span><span id="L-55"><a href="#L-55"><span class="linenos"> 55</span></a> <span class="p">)</span>
</span><span id="L-56"><a href="#L-56"><span class="linenos"> 56</span></a>
</span><span id="L-57"><a href="#L-57"><span class="linenos"> 57</span></a> <span class="c1"># Map of Expression->alias</span>
</span><span id="L-58"><a href="#L-58"><span class="linenos"> 58</span></a> <span class="c1"># Existing CTES in the root expression. We'll use this for deduplication.</span>
</span><span id="L-59"><a href="#L-59"><span class="linenos"> 59</span></a> <span class="n">existing_ctes</span> <span class="o">=</span> <span class="p">{}</span>
</span><span id="L-60"><a href="#L-60"><span class="linenos"> 60</span></a>
</span><span id="L-61"><a href="#L-61"><span class="linenos"> 61</span></a> <span class="n">with_</span> <span class="o">=</span> <span class="n">root</span><span class="o">.</span><span class="n">expression</span><span class="o">.</span><span class="n">args</span><span class="o">.</span><span class="n">get</span><span class="p">(</span><span class="s2">"with"</span><span class="p">)</span>
</span><span id="L-62"><a href="#L-62"><span class="linenos"> 62</span></a> <span class="n">recursive</span> <span class="o">=</span> <span class="kc">False</span>
</span><span id="L-63"><a href="#L-63"><span class="linenos"> 63</span></a> <span class="k">if</span> <span class="n">with_</span><span class="p">:</span>
</span><span id="L-64"><a href="#L-64"><span class="linenos"> 64</span></a> <span class="n">recursive</span> <span class="o">=</span> <span class="n">with_</span><span class="o">.</span><span class="n">args</span><span class="o">.</span><span class="n">get</span><span class="p">(</span><span class="s2">"recursive"</span><span class="p">)</span>
</span><span id="L-65"><a href="#L-65"><span class="linenos"> 65</span></a> <span class="k">for</span> <span class="n">cte</span> <span class="ow">in</span> <span class="n">with_</span><span class="o">.</span><span class="n">expressions</span><span class="p">:</span>
</span><span id="L-66"><a href="#L-66"><span class="linenos"> 66</span></a> <span class="n">existing_ctes</span><span class="p">[</span><span class="n">cte</span><span class="o">.</span><span class="n">this</span><span class="p">]</span> <span class="o">=</span> <span class="n">cte</span><span class="o">.</span><span class="n">alias</span>
</span><span id="L-67"><a href="#L-67"><span class="linenos"> 67</span></a> <span class="n">new_ctes</span> <span class="o">=</span> <span class="p">[]</span>
</span><span id="L-68"><a href="#L-68"><span class="linenos"> 68</span></a>
</span><span id="L-69"><a href="#L-69"><span class="linenos"> 69</span></a> <span class="c1"># We're adding more CTEs, but we want to maintain the DAG order.</span>
</span><span id="L-70"><a href="#L-70"><span class="linenos"> 70</span></a> <span class="c1"># Derived tables within an existing CTE need to come before the existing CTE.</span>
</span><span id="L-71"><a href="#L-71"><span class="linenos"> 71</span></a> <span class="k">for</span> <span class="n">cte_scope</span> <span class="ow">in</span> <span class="n">root</span><span class="o">.</span><span class="n">cte_scopes</span><span class="p">:</span>
</span><span id="L-72"><a href="#L-72"><span class="linenos"> 72</span></a> <span class="c1"># Append all the new CTEs from this existing CTE</span>
</span><span id="L-73"><a href="#L-73"><span class="linenos"> 73</span></a> <span class="k">for</span> <span class="n">scope</span> <span class="ow">in</span> <span class="n">cte_scope</span><span class="o">.</span><span class="n">traverse</span><span class="p">():</span>
</span><span id="L-74"><a href="#L-74"><span class="linenos"> 74</span></a> <span class="k">if</span> <span class="n">scope</span> <span class="ow">is</span> <span class="n">cte_scope</span><span class="p">:</span>
</span><span id="L-75"><a href="#L-75"><span class="linenos"> 75</span></a> <span class="c1"># Don't try to eliminate this CTE itself</span>
</span><span id="L-76"><a href="#L-76"><span class="linenos"> 76</span></a> <span class="k">continue</span>
</span><span id="L-77"><a href="#L-77"><span class="linenos"> 77</span></a> <span class="n">new_cte</span> <span class="o">=</span> <span class="n">_eliminate</span><span class="p">(</span><span class="n">scope</span><span class="p">,</span> <span class="n">existing_ctes</span><span class="p">,</span> <span class="n">taken</span><span class="p">)</span>
</span><span id="L-78"><a href="#L-78"><span class="linenos"> 78</span></a> <span class="k">if</span> <span class="n">new_cte</span><span class="p">:</span>
</span><span id="L-79"><a href="#L-79"><span class="linenos"> 79</span></a> <span class="n">new_ctes</span><span class="o">.</span><span class="n">append</span><span class="p">(</span><span class="n">new_cte</span><span class="p">)</span>
</span><span id="L-80"><a href="#L-80"><span class="linenos"> 80</span></a>
</span><span id="L-81"><a href="#L-81"><span class="linenos"> 81</span></a> <span class="c1"># Append the existing CTE itself</span>
</span><span id="L-82"><a href="#L-82"><span class="linenos"> 82</span></a> <span class="n">new_ctes</span><span class="o">.</span><span class="n">append</span><span class="p">(</span><span class="n">cte_scope</span><span class="o">.</span><span class="n">expression</span><span class="o">.</span><span class="n">parent</span><span class="p">)</span>
</span><span id="L-83"><a href="#L-83"><span class="linenos"> 83</span></a>
</span><span id="L-84"><a href="#L-84"><span class="linenos"> 84</span></a> <span class="c1"># Now append the rest</span>
</span><span id="L-85"><a href="#L-85"><span class="linenos"> 85</span></a> <span class="k">for</span> <span class="n">scope</span> <span class="ow">in</span> <span class="n">itertools</span><span class="o">.</span><span class="n">chain</span><span class="p">(</span><span class="n">root</span><span class="o">.</span><span class="n">union_scopes</span><span class="p">,</span> <span class="n">root</span><span class="o">.</span><span class="n">subquery_scopes</span><span class="p">,</span> <span class="n">root</span><span class="o">.</span><span class="n">table_scopes</span><span class="p">):</span>
</span><span id="L-86"><a href="#L-86"><span class="linenos"> 86</span></a> <span class="k">for</span> <span class="n">child_scope</span> <span class="ow">in</span> <span class="n">scope</span><span class="o">.</span><span class="n">traverse</span><span class="p">():</span>
</span><span id="L-87"><a href="#L-87"><span class="linenos"> 87</span></a> <span class="n">new_cte</span> <span class="o">=</span> <span class="n">_eliminate</span><span class="p">(</span><span class="n">child_scope</span><span class="p">,</span> <span class="n">existing_ctes</span><span class="p">,</span> <span class="n">taken</span><span class="p">)</span>
</span><span id="L-88"><a href="#L-88"><span class="linenos"> 88</span></a> <span class="k">if</span> <span class="n">new_cte</span><span class="p">:</span>
</span><span id="L-89"><a href="#L-89"><span class="linenos"> 89</span></a> <span class="n">new_ctes</span><span class="o">.</span><span class="n">append</span><span class="p">(</span><span class="n">new_cte</span><span class="p">)</span>
</span><span id="L-90"><a href="#L-90"><span class="linenos"> 90</span></a>
</span><span id="L-91"><a href="#L-91"><span class="linenos"> 91</span></a> <span class="k">if</span> <span class="n">new_ctes</span><span class="p">:</span>
</span><span id="L-92"><a href="#L-92"><span class="linenos"> 92</span></a> <span class="n">expression</span><span class="o">.</span><span class="n">set</span><span class="p">(</span><span class="s2">"with"</span><span class="p">,</span> <span class="n">exp</span><span class="o">.</span><span class="n">With</span><span class="p">(</span><span class="n">expressions</span><span class="o">=</span><span class="n">new_ctes</span><span class="p">,</span> <span class="n">recursive</span><span class="o">=</span><span class="n">recursive</span><span class="p">))</span>
</span><span id="L-93"><a href="#L-93"><span class="linenos"> 93</span></a>
</span><span id="L-94"><a href="#L-94"><span class="linenos"> 94</span></a> <span class="k">return</span> <span class="n">expression</span>
</span><span id="L-95"><a href="#L-95"><span class="linenos"> 95</span></a>
</span><span id="L-96"><a href="#L-96"><span class="linenos"> 96</span></a>
</span><span id="L-97"><a href="#L-97"><span class="linenos"> 97</span></a><span class="k">def</span> <span class="nf">_eliminate</span><span class="p">(</span><span class="n">scope</span><span class="p">,</span> <span class="n">existing_ctes</span><span class="p">,</span> <span class="n">taken</span><span class="p">):</span>
</span><span id="L-98"><a href="#L-98"><span class="linenos"> 98</span></a> <span class="k">if</span> <span class="n">scope</span><span class="o">.</span><span class="n">is_union</span><span class="p">:</span>
</span><span id="L-99"><a href="#L-99"><span class="linenos"> 99</span></a> <span class="k">return</span> <span class="n">_eliminate_union</span><span class="p">(</span><span class="n">scope</span><span class="p">,</span> <span class="n">existing_ctes</span><span class="p">,</span> <span class="n">taken</span><span class="p">)</span>
</span><span id="L-100"><a href="#L-100"><span class="linenos">100</span></a>
</span><span id="L-101"><a href="#L-101"><span class="linenos">101</span></a> <span class="k">if</span> <span class="n">scope</span><span class="o">.</span><span class="n">is_derived_table</span><span class="p">:</span>
</span><span id="L-102"><a href="#L-102"><span class="linenos">102</span></a> <span class="k">return</span> <span class="n">_eliminate_derived_table</span><span class="p">(</span><span class="n">scope</span><span class="p">,</span> <span class="n">existing_ctes</span><span class="p">,</span> <span class="n">taken</span><span class="p">)</span>
</span><span id="L-103"><a href="#L-103"><span class="linenos">103</span></a>
</span><span id="L-104"><a href="#L-104"><span class="linenos">104</span></a> <span class="k">if</span> <span class="n">scope</span><span class="o">.</span><span class="n">is_cte</span><span class="p">:</span>
</span><span id="L-105"><a href="#L-105"><span class="linenos">105</span></a> <span class="k">return</span> <span class="n">_eliminate_cte</span><span class="p">(</span><span class="n">scope</span><span class="p">,</span> <span class="n">existing_ctes</span><span class="p">,</span> <span class="n">taken</span><span class="p">)</span>
</span><span id="L-106"><a href="#L-106"><span class="linenos">106</span></a>
</span><span id="L-107"><a href="#L-107"><span class="linenos">107</span></a>
</span><span id="L-108"><a href="#L-108"><span class="linenos">108</span></a><span class="k">def</span> <span class="nf">_eliminate_union</span><span class="p">(</span><span class="n">scope</span><span class="p">,</span> <span class="n">existing_ctes</span><span class="p">,</span> <span class="n">taken</span><span class="p">):</span>
</span><span id="L-109"><a href="#L-109"><span class="linenos">109</span></a> <span class="n">duplicate_cte_alias</span> <span class="o">=</span> <span class="n">existing_ctes</span><span class="o">.</span><span class="n">get</span><span class="p">(</span><span class="n">scope</span><span class="o">.</span><span class="n">expression</span><span class="p">)</span>
</span><span id="L-110"><a href="#L-110"><span class="linenos">110</span></a>
</span><span id="L-111"><a href="#L-111"><span class="linenos">111</span></a> <span class="n">alias</span> <span class="o">=</span> <span class="n">duplicate_cte_alias</span> <span class="ow">or</span> <span class="n">find_new_name</span><span class="p">(</span><span class="n">taken</span><span class="o">=</span><span class="n">taken</span><span class="p">,</span> <span class="n">base</span><span class="o">=</span><span class="s2">"cte"</span><span class="p">)</span>
</span><span id="L-112"><a href="#L-112"><span class="linenos">112</span></a>
</span><span id="L-113"><a href="#L-113"><span class="linenos">113</span></a> <span class="n">taken</span><span class="p">[</span><span class="n">alias</span><span class="p">]</span> <span class="o">=</span> <span class="n">scope</span>
</span><span id="L-114"><a href="#L-114"><span class="linenos">114</span></a>
</span><span id="L-115"><a href="#L-115"><span class="linenos">115</span></a> <span class="c1"># Try to maintain the selections</span>
</span><span id="L-116"><a href="#L-116"><span class="linenos">116</span></a> <span class="n">expressions</span> <span class="o">=</span> <span class="n">scope</span><span class="o">.</span><span class="n">selects</span>
</span><span id="L-117"><a href="#L-117"><span class="linenos">117</span></a> <span class="n">selects</span> <span class="o">=</span> <span class="p">[</span>
</span><span id="L-118"><a href="#L-118"><span class="linenos">118</span></a> <span class="n">exp</span><span class="o">.</span><span class="n">alias_</span><span class="p">(</span><span class="n">exp</span><span class="o">.</span><span class="n">column</span><span class="p">(</span><span class="n">e</span><span class="o">.</span><span class="n">alias_or_name</span><span class="p">,</span> <span class="n">table</span><span class="o">=</span><span class="n">alias</span><span class="p">),</span> <span class="n">alias</span><span class="o">=</span><span class="n">e</span><span class="o">.</span><span class="n">alias_or_name</span><span class="p">,</span> <span class="n">copy</span><span class="o">=</span><span class="kc">False</span><span class="p">)</span>
</span><span id="L-119"><a href="#L-119"><span class="linenos">119</span></a> <span class="k">for</span> <span class="n">e</span> <span class="ow">in</span> <span class="n">expressions</span>
</span><span id="L-120"><a href="#L-120"><span class="linenos">120</span></a> <span class="k">if</span> <span class="n">e</span><span class="o">.</span><span class="n">alias_or_name</span>
</span><span id="L-121"><a href="#L-121"><span class="linenos">121</span></a> <span class="p">]</span>
</span><span id="L-122"><a href="#L-122"><span class="linenos">122</span></a> <span class="c1"># If not all selections have an alias, just select *</span>
</span><span id="L-123"><a href="#L-123"><span class="linenos">123</span></a> <span class="k">if</span> <span class="nb">len</span><span class="p">(</span><span class="n">selects</span><span class="p">)</span> <span class="o">!=</span> <span class="nb">len</span><span class="p">(</span><span class="n">expressions</span><span class="p">):</span>
</span><span id="L-124"><a href="#L-124"><span class="linenos">124</span></a> <span class="n">selects</span> <span class="o">=</span> <span class="p">[</span><span class="s2">"*"</span><span class="p">]</span>
</span><span id="L-125"><a href="#L-125"><span class="linenos">125</span></a>
</span><span id="L-126"><a href="#L-126"><span class="linenos">126</span></a> <span class="n">scope</span><span class="o">.</span><span class="n">expression</span><span class="o">.</span><span class="n">replace</span><span class="p">(</span>
</span><span id="L-127"><a href="#L-127"><span class="linenos">127</span></a> <span class="n">exp</span><span class="o">.</span><span class="n">select</span><span class="p">(</span><span class="o">*</span><span class="n">selects</span><span class="p">)</span><span class="o">.</span><span class="n">from_</span><span class="p">(</span><span class="n">exp</span><span class="o">.</span><span class="n">alias_</span><span class="p">(</span><span class="n">exp</span><span class="o">.</span><span class="n">table_</span><span class="p">(</span><span class="n">alias</span><span class="p">),</span> <span class="n">alias</span><span class="o">=</span><span class="n">alias</span><span class="p">,</span> <span class="n">copy</span><span class="o">=</span><span class="kc">False</span><span class="p">))</span>
</span><span id="L-128"><a href="#L-128"><span class="linenos">128</span></a> <span class="p">)</span>
</span><span id="L-129"><a href="#L-129"><span class="linenos">129</span></a>
</span><span id="L-130"><a href="#L-130"><span class="linenos">130</span></a> <span class="k">if</span> <span class="ow">not</span> <span class="n">duplicate_cte_alias</span><span class="p">:</span>
</span><span id="L-131"><a href="#L-131"><span class="linenos">131</span></a> <span class="n">existing_ctes</span><span class="p">[</span><span class="n">scope</span><span class="o">.</span><span class="n">expression</span><span class="p">]</span> <span class="o">=</span> <span class="n">alias</span>
</span><span id="L-132"><a href="#L-132"><span class="linenos">132</span></a> <span class="k">return</span> <span class="n">exp</span><span class="o">.</span><span class="n">CTE</span><span class="p">(</span>
</span><span id="L-133"><a href="#L-133"><span class="linenos">133</span></a> <span class="n">this</span><span class="o">=</span><span class="n">scope</span><span class="o">.</span><span class="n">expression</span><span class="p">,</span>
</span><span id="L-134"><a href="#L-134"><span class="linenos">134</span></a> <span class="n">alias</span><span class="o">=</span><span class="n">exp</span><span class="o">.</span><span class="n">TableAlias</span><span class="p">(</span><span class="n">this</span><span class="o">=</span><span class="n">exp</span><span class="o">.</span><span class="n">to_identifier</span><span class="p">(</span><span class="n">alias</span><span class="p">)),</span>
</span><span id="L-135"><a href="#L-135"><span class="linenos">135</span></a> <span class="p">)</span>
</span><span id="L-136"><a href="#L-136"><span class="linenos">136</span></a>
</span><span id="L-137"><a href="#L-137"><span class="linenos">137</span></a>
</span><span id="L-138"><a href="#L-138"><span class="linenos">138</span></a><span class="k">def</span> <span class="nf">_eliminate_derived_table</span><span class="p">(</span><span class="n">scope</span><span class="p">,</span> <span class="n">existing_ctes</span><span class="p">,</span> <span class="n">taken</span><span class="p">):</span>
</span><span id="L-139"><a href="#L-139"><span class="linenos">139</span></a> <span class="c1"># This ensures we don't drop the "pivot" arg from a pivoted subquery</span>
</span><span id="L-140"><a href="#L-140"><span class="linenos">140</span></a> <span class="k">if</span> <span class="n">scope</span><span class="o">.</span><span class="n">parent</span><span class="o">.</span><span class="n">pivots</span><span class="p">:</span>
</span><span id="L-141"><a href="#L-141"><span class="linenos">141</span></a> <span class="k">return</span> <span class="kc">None</span>
</span><span id="L-142"><a href="#L-142"><span class="linenos">142</span></a>
</span><span id="L-143"><a href="#L-143"><span class="linenos">143</span></a> <span class="n">parent</span> <span class="o">=</span> <span class="n">scope</span><span class="o">.</span><span class="n">expression</span><span class="o">.</span><span class="n">parent</span>
</span><span id="L-144"><a href="#L-144"><span class="linenos">144</span></a> <span class="n">name</span><span class="p">,</span> <span class="n">cte</span> <span class="o">=</span> <span class="n">_new_cte</span><span class="p">(</span><span class="n">scope</span><span class="p">,</span> <span class="n">existing_ctes</span><span class="p">,</span> <span class="n">taken</span><span class="p">)</span>
</span><span id="L-145"><a href="#L-145"><span class="linenos">145</span></a>
</span><span id="L-146"><a href="#L-146"><span class="linenos">146</span></a> <span class="n">table</span> <span class="o">=</span> <span class="n">exp</span><span class="o">.</span><span class="n">alias_</span><span class="p">(</span><span class="n">exp</span><span class="o">.</span><span class="n">table_</span><span class="p">(</span><span class="n">name</span><span class="p">),</span> <span class="n">alias</span><span class="o">=</span><span class="n">parent</span><span class="o">.</span><span class="n">alias</span> <span class="ow">or</span> <span class="n">name</span><span class="p">)</span>
</span><span id="L-147"><a href="#L-147"><span class="linenos">147</span></a> <span class="n">parent</span><span class="o">.</span><span class="n">replace</span><span class="p">(</span><span class="n">table</span><span class="p">)</span>
</span><span id="L-148"><a href="#L-148"><span class="linenos">148</span></a>
</span><span id="L-149"><a href="#L-149"><span class="linenos">149</span></a> <span class="k">return</span> <span class="n">cte</span>
</span><span id="L-150"><a href="#L-150"><span class="linenos">150</span></a>
</span><span id="L-151"><a href="#L-151"><span class="linenos">151</span></a>
</span><span id="L-152"><a href="#L-152"><span class="linenos">152</span></a><span class="k">def</span> <span class="nf">_eliminate_cte</span><span class="p">(</span><span class="n">scope</span><span class="p">,</span> <span class="n">existing_ctes</span><span class="p">,</span> <span class="n">taken</span><span class="p">):</span>
</span><span id="L-153"><a href="#L-153"><span class="linenos">153</span></a> <span class="n">parent</span> <span class="o">=</span> <span class="n">scope</span><span class="o">.</span><span class="n">expression</span><span class="o">.</span><span class="n">parent</span>
</span><span id="L-154"><a href="#L-154"><span class="linenos">154</span></a> <span class="n">name</span><span class="p">,</span> <span class="n">cte</span> <span class="o">=</span> <span class="n">_new_cte</span><span class="p">(</span><span class="n">scope</span><span class="p">,</span> <span class="n">existing_ctes</span><span class="p">,</span> <span class="n">taken</span><span class="p">)</span>
</span><span id="L-155"><a href="#L-155"><span class="linenos">155</span></a>
</span><span id="L-156"><a href="#L-156"><span class="linenos">156</span></a> <span class="n">with_</span> <span class="o">=</span> <span class="n">parent</span><span class="o">.</span><span class="n">parent</span>
</span><span id="L-157"><a href="#L-157"><span class="linenos">157</span></a> <span class="n">parent</span><span class="o">.</span><span class="n">pop</span><span class="p">()</span>
</span><span id="L-158"><a href="#L-158"><span class="linenos">158</span></a> <span class="k">if</span> <span class="ow">not</span> <span class="n">with_</span><span class="o">.</span><span class="n">expressions</span><span class="p">:</span>
</span><span id="L-159"><a href="#L-159"><span class="linenos">159</span></a> <span class="n">with_</span><span class="o">.</span><span class="n">pop</span><span class="p">()</span>
</span><span id="L-160"><a href="#L-160"><span class="linenos">160</span></a>
</span><span id="L-161"><a href="#L-161"><span class="linenos">161</span></a> <span class="c1"># Rename references to this CTE</span>
</span><span id="L-162"><a href="#L-162"><span class="linenos">162</span></a> <span class="k">for</span> <span class="n">child_scope</span> <span class="ow">in</span> <span class="n">scope</span><span class="o">.</span><span class="n">parent</span><span class="o">.</span><span class="n">traverse</span><span class="p">():</span>
</span><span id="L-163"><a href="#L-163"><span class="linenos">163</span></a> <span class="k">for</span> <span class="n">table</span><span class="p">,</span> <span class="n">source</span> <span class="ow">in</span> <span class="n">child_scope</span><span class="o">.</span><span class="n">selected_sources</span><span class="o">.</span><span class="n">values</span><span class="p">():</span>
</span><span id="L-164"><a href="#L-164"><span class="linenos">164</span></a> <span class="k">if</span> <span class="n">source</span> <span class="ow">is</span> <span class="n">scope</span><span class="p">:</span>
</span><span id="L-165"><a href="#L-165"><span class="linenos">165</span></a> <span class="n">new_table</span> <span class="o">=</span> <span class="n">exp</span><span class="o">.</span><span class="n">alias_</span><span class="p">(</span><span class="n">exp</span><span class="o">.</span><span class="n">table_</span><span class="p">(</span><span class="n">name</span><span class="p">),</span> <span class="n">alias</span><span class="o">=</span><span class="n">table</span><span class="o">.</span><span class="n">alias_or_name</span><span class="p">,</span> <span class="n">copy</span><span class="o">=</span><span class="kc">False</span><span class="p">)</span>
</span><span id="L-166"><a href="#L-166"><span class="linenos">166</span></a> <span class="n">table</span><span class="o">.</span><span class="n">replace</span><span class="p">(</span><span class="n">new_table</span><span class="p">)</span>
</span><span id="L-167"><a href="#L-167"><span class="linenos">167</span></a>
</span><span id="L-168"><a href="#L-168"><span class="linenos">168</span></a> <span class="k">return</span> <span class="n">cte</span>
</span><span id="L-169"><a href="#L-169"><span class="linenos">169</span></a>
</span><span id="L-170"><a href="#L-170"><span class="linenos">170</span></a>
</span><span id="L-171"><a href="#L-171"><span class="linenos">171</span></a><span class="k">def</span> <span class="nf">_new_cte</span><span class="p">(</span><span class="n">scope</span><span class="p">,</span> <span class="n">existing_ctes</span><span class="p">,</span> <span class="n">taken</span><span class="p">):</span>
</span><span id="L-172"><a href="#L-172"><span class="linenos">172</span></a><span class="w"> </span><span class="sd">"""</span>
</span><span id="L-173"><a href="#L-173"><span class="linenos">173</span></a><span class="sd"> Returns:</span>
</span><span id="L-174"><a href="#L-174"><span class="linenos">174</span></a><span class="sd"> tuple of (name, cte)</span>
</span><span id="L-175"><a href="#L-175"><span class="linenos">175</span></a><span class="sd"> where `name` is a new name for this CTE in the root scope and `cte` is a new CTE instance.</span>
</span><span id="L-176"><a href="#L-176"><span class="linenos">176</span></a><span class="sd"> If this CTE duplicates an existing CTE, `cte` will be None.</span>
</span><span id="L-177"><a href="#L-177"><span class="linenos">177</span></a><span class="sd"> """</span>
</span><span id="L-178"><a href="#L-178"><span class="linenos">178</span></a> <span class="n">duplicate_cte_alias</span> <span class="o">=</span> <span class="n">existing_ctes</span><span class="o">.</span><span class="n">get</span><span class="p">(</span><span class="n">scope</span><span class="o">.</span><span class="n">expression</span><span class="p">)</span>
</span><span id="L-179"><a href="#L-179"><span class="linenos">179</span></a> <span class="n">parent</span> <span class="o">=</span> <span class="n">scope</span><span class="o">.</span><span class="n">expression</span><span class="o">.</span><span class="n">parent</span>
</span><span id="L-180"><a href="#L-180"><span class="linenos">180</span></a> <span class="n">name</span> <span class="o">=</span> <span class="n">parent</span><span class="o">.</span><span class="n">alias</span>
</span><span id="L-181"><a href="#L-181"><span class="linenos">181</span></a>
</span><span id="L-182"><a href="#L-182"><span class="linenos">182</span></a> <span class="k">if</span> <span class="ow">not</span> <span class="n">name</span><span class="p">:</span>
</span><span id="L-183"><a href="#L-183"><span class="linenos">183</span></a> <span class="n">name</span> <span class="o">=</span> <span class="n">find_new_name</span><span class="p">(</span><span class="n">taken</span><span class="o">=</span><span class="n">taken</span><span class="p">,</span> <span class="n">base</span><span class="o">=</span><span class="s2">"cte"</span><span class="p">)</span>
</span><span id="L-184"><a href="#L-184"><span class="linenos">184</span></a>
</span><span id="L-185"><a href="#L-185"><span class="linenos">185</span></a> <span class="k">if</span> <span class="n">duplicate_cte_alias</span><span class="p">:</span>
</span><span id="L-186"><a href="#L-186"><span class="linenos">186</span></a> <span class="n">name</span> <span class="o">=</span> <span class="n">duplicate_cte_alias</span>
</span><span id="L-187"><a href="#L-187"><span class="linenos">187</span></a> <span class="k">elif</span> <span class="n">taken</span><span class="o">.</span><span class="n">get</span><span class="p">(</span><span class="n">name</span><span class="p">):</span>
</span><span id="L-188"><a href="#L-188"><span class="linenos">188</span></a> <span class="n">name</span> <span class="o">=</span> <span class="n">find_new_name</span><span class="p">(</span><span class="n">taken</span><span class="o">=</span><span class="n">taken</span><span class="p">,</span> <span class="n">base</span><span class="o">=</span><span class="n">name</span><span class="p">)</span>
</span><span id="L-189"><a href="#L-189"><span class="linenos">189</span></a>
</span><span id="L-190"><a href="#L-190"><span class="linenos">190</span></a> <span class="n">taken</span><span class="p">[</span><span class="n">name</span><span class="p">]</span> <span class="o">=</span> <span class="n">scope</span>
</span><span id="L-191"><a href="#L-191"><span class="linenos">191</span></a>
</span><span id="L-192"><a href="#L-192"><span class="linenos">192</span></a> <span class="k">if</span> <span class="ow">not</span> <span class="n">duplicate_cte_alias</span><span class="p">:</span>
</span><span id="L-193"><a href="#L-193"><span class="linenos">193</span></a> <span class="n">existing_ctes</span><span class="p">[</span><span class="n">scope</span><span class="o">.</span><span class="n">expression</span><span class="p">]</span> <span class="o">=</span> <span class="n">name</span>
</span><span id="L-194"><a href="#L-194"><span class="linenos">194</span></a> <span class="n">cte</span> <span class="o">=</span> <span class="n">exp</span><span class="o">.</span><span class="n">CTE</span><span class="p">(</span>
</span><span id="L-195"><a href="#L-195"><span class="linenos">195</span></a> <span class="n">this</span><span class="o">=</span><span class="n">scope</span><span class="o">.</span><span class="n">expression</span><span class="p">,</span>
</span><span id="L-196"><a href="#L-196"><span class="linenos">196</span></a> <span class="n">alias</span><span class="o">=</span><span class="n">exp</span><span class="o">.</span><span class="n">TableAlias</span><span class="p">(</span><span class="n">this</span><span class="o">=</span><span class="n">exp</span><span class="o">.</span><span class="n">to_identifier</span><span class="p">(</span><span class="n">name</span><span class="p">)),</span>
</span><span id="L-197"><a href="#L-197"><span class="linenos">197</span></a> <span class="p">)</span>
</span><span id="L-198"><a href="#L-198"><span class="linenos">198</span></a> <span class="k">else</span><span class="p">:</span>
</span><span id="L-199"><a href="#L-199"><span class="linenos">199</span></a> <span class="n">cte</span> <span class="o">=</span> <span class="kc">None</span>
</span><span id="L-200"><a href="#L-200"><span class="linenos">200</span></a> <span class="k">return</span> <span class="n">name</span><span class="p">,</span> <span class="n">cte</span>
</span></pre></div>
</section>
<section id="eliminate_subqueries">
<input id="eliminate_subqueries-view-source" class="view-source-toggle-state" type="checkbox" aria-hidden="true" tabindex="-1">
<div class="attr function">
<span class="def">def</span>
<span class="name">eliminate_subqueries</span><span class="signature pdoc-code condensed">(<span class="param"><span class="n">expression</span></span><span class="return-annotation">):</span></span>
<label class="view-source-button" for="eliminate_subqueries-view-source"><span>View Source</span></label>
</div>
<a class="headerlink" href="#eliminate_subqueries"></a>
<div class="pdoc-code codehilite"><pre><span></span><span id="eliminate_subqueries-9"><a href="#eliminate_subqueries-9"><span class="linenos"> 9</span></a><span class="k">def</span> <span class="nf">eliminate_subqueries</span><span class="p">(</span><span class="n">expression</span><span class="p">):</span>
</span><span id="eliminate_subqueries-10"><a href="#eliminate_subqueries-10"><span class="linenos">10</span></a><span class="w"> </span><span class="sd">"""</span>
</span><span id="eliminate_subqueries-11"><a href="#eliminate_subqueries-11"><span class="linenos">11</span></a><span class="sd"> Rewrite derived tables as CTES, deduplicating if possible.</span>
</span><span id="eliminate_subqueries-12"><a href="#eliminate_subqueries-12"><span class="linenos">12</span></a>
</span><span id="eliminate_subqueries-13"><a href="#eliminate_subqueries-13"><span class="linenos">13</span></a><span class="sd"> Example:</span>
</span><span id="eliminate_subqueries-14"><a href="#eliminate_subqueries-14"><span class="linenos">14</span></a><span class="sd"> >>> import sqlglot</span>
</span><span id="eliminate_subqueries-15"><a href="#eliminate_subqueries-15"><span class="linenos">15</span></a><span class="sd"> >>> expression = sqlglot.parse_one("SELECT a FROM (SELECT * FROM x) AS y")</span>
</span><span id="eliminate_subqueries-16"><a href="#eliminate_subqueries-16"><span class="linenos">16</span></a><span class="sd"> >>> eliminate_subqueries(expression).sql()</span>
</span><span id="eliminate_subqueries-17"><a href="#eliminate_subqueries-17"><span class="linenos">17</span></a><span class="sd"> 'WITH y AS (SELECT * FROM x) SELECT a FROM y AS y'</span>
</span><span id="eliminate_subqueries-18"><a href="#eliminate_subqueries-18"><span class="linenos">18</span></a>
</span><span id="eliminate_subqueries-19"><a href="#eliminate_subqueries-19"><span class="linenos">19</span></a><span class="sd"> This also deduplicates common subqueries:</span>
</span><span id="eliminate_subqueries-20"><a href="#eliminate_subqueries-20"><span class="linenos">20</span></a><span class="sd"> >>> expression = sqlglot.parse_one("SELECT a FROM (SELECT * FROM x) AS y CROSS JOIN (SELECT * FROM x) AS z")</span>
</span><span id="eliminate_subqueries-21"><a href="#eliminate_subqueries-21"><span class="linenos">21</span></a><span class="sd"> >>> eliminate_subqueries(expression).sql()</span>
</span><span id="eliminate_subqueries-22"><a href="#eliminate_subqueries-22"><span class="linenos">22</span></a><span class="sd"> 'WITH y AS (SELECT * FROM x) SELECT a FROM y AS y CROSS JOIN y AS z'</span>
</span><span id="eliminate_subqueries-23"><a href="#eliminate_subqueries-23"><span class="linenos">23</span></a>
</span><span id="eliminate_subqueries-24"><a href="#eliminate_subqueries-24"><span class="linenos">24</span></a><span class="sd"> Args:</span>
</span><span id="eliminate_subqueries-25"><a href="#eliminate_subqueries-25"><span class="linenos">25</span></a><span class="sd"> expression (sqlglot.Expression): expression</span>
</span><span id="eliminate_subqueries-26"><a href="#eliminate_subqueries-26"><span class="linenos">26</span></a><span class="sd"> Returns:</span>
</span><span id="eliminate_subqueries-27"><a href="#eliminate_subqueries-27"><span class="linenos">27</span></a><span class="sd"> sqlglot.Expression: expression</span>
</span><span id="eliminate_subqueries-28"><a href="#eliminate_subqueries-28"><span class="linenos">28</span></a><span class="sd"> """</span>
</span><span id="eliminate_subqueries-29"><a href="#eliminate_subqueries-29"><span class="linenos">29</span></a> <span class="k">if</span> <span class="nb">isinstance</span><span class="p">(</span><span class="n">expression</span><span class="p">,</span> <span class="n">exp</span><span class="o">.</span><span class="n">Subquery</span><span class="p">):</span>
</span><span id="eliminate_subqueries-30"><a href="#eliminate_subqueries-30"><span class="linenos">30</span></a> <span class="c1"># It's possible to have subqueries at the root, e.g. (SELECT * FROM x) LIMIT 1</span>
</span><span id="eliminate_subqueries-31"><a href="#eliminate_subqueries-31"><span class="linenos">31</span></a> <span class="n">eliminate_subqueries</span><span class="p">(</span><span class="n">expression</span><span class="o">.</span><span class="n">this</span><span class="p">)</span>
</span><span id="eliminate_subqueries-32"><a href="#eliminate_subqueries-32"><span class="linenos">32</span></a> <span class="k">return</span> <span class="n">expression</span>
</span><span id="eliminate_subqueries-33"><a href="#eliminate_subqueries-33"><span class="linenos">33</span></a>
</span><span id="eliminate_subqueries-34"><a href="#eliminate_subqueries-34"><span class="linenos">34</span></a> <span class="n">root</span> <span class="o">=</span> <span class="n">build_scope</span><span class="p">(</span><span class="n">expression</span><span class="p">)</span>
</span><span id="eliminate_subqueries-35"><a href="#eliminate_subqueries-35"><span class="linenos">35</span></a>
</span><span id="eliminate_subqueries-36"><a href="#eliminate_subqueries-36"><span class="linenos">36</span></a> <span class="k">if</span> <span class="ow">not</span> <span class="n">root</span><span class="p">:</span>
</span><span id="eliminate_subqueries-37"><a href="#eliminate_subqueries-37"><span class="linenos">37</span></a> <span class="k">return</span> <span class="n">expression</span>
</span><span id="eliminate_subqueries-38"><a href="#eliminate_subqueries-38"><span class="linenos">38</span></a>
</span><span id="eliminate_subqueries-39"><a href="#eliminate_subqueries-39"><span class="linenos">39</span></a> <span class="c1"># Map of alias->Scope|Table</span>
</span><span id="eliminate_subqueries-40"><a href="#eliminate_subqueries-40"><span class="linenos">40</span></a> <span class="c1"># These are all aliases that are already used in the expression.</span>
</span><span id="eliminate_subqueries-41"><a href="#eliminate_subqueries-41"><span class="linenos">41</span></a> <span class="c1"># We don't want to create new CTEs that conflict with these names.</span>
</span><span id="eliminate_subqueries-42"><a href="#eliminate_subqueries-42"><span class="linenos">42</span></a> <span class="n">taken</span> <span class="o">=</span> <span class="p">{}</span>
</span><span id="eliminate_subqueries-43"><a href="#eliminate_subqueries-43"><span class="linenos">43</span></a>
</span><span id="eliminate_subqueries-44"><a href="#eliminate_subqueries-44"><span class="linenos">44</span></a> <span class="c1"># All CTE aliases in the root scope are taken</span>
</span><span id="eliminate_subqueries-45"><a href="#eliminate_subqueries-45"><span class="linenos">45</span></a> <span class="k">for</span> <span class="n">scope</span> <span class="ow">in</span> <span class="n">root</span><span class="o">.</span><span class="n">cte_scopes</span><span class="p">:</span>
</span><span id="eliminate_subqueries-46"><a href="#eliminate_subqueries-46"><span class="linenos">46</span></a> <span class="n">taken</span><span class="p">[</span><span class="n">scope</span><span class="o">.</span><span class="n">expression</span><span class="o">.</span><span class="n">parent</span><span class="o">.</span><span class="n">alias</span><span class="p">]</span> <span class="o">=</span> <span class="n">scope</span>
</span><span id="eliminate_subqueries-47"><a href="#eliminate_subqueries-47"><span class="linenos">47</span></a>
</span><span id="eliminate_subqueries-48"><a href="#eliminate_subqueries-48"><span class="linenos">48</span></a> <span class="c1"># All table names are taken</span>
</span><span id="eliminate_subqueries-49"><a href="#eliminate_subqueries-49"><span class="linenos">49</span></a> <span class="k">for</span> <span class="n">scope</span> <span class="ow">in</span> <span class="n">root</span><span class="o">.</span><span class="n">traverse</span><span class="p">():</span>
</span><span id="eliminate_subqueries-50"><a href="#eliminate_subqueries-50"><span class="linenos">50</span></a> <span class="n">taken</span><span class="o">.</span><span class="n">update</span><span class="p">(</span>
</span><span id="eliminate_subqueries-51"><a href="#eliminate_subqueries-51"><span class="linenos">51</span></a> <span class="p">{</span>
</span><span id="eliminate_subqueries-52"><a href="#eliminate_subqueries-52"><span class="linenos">52</span></a> <span class="n">source</span><span class="o">.</span><span class="n">name</span><span class="p">:</span> <span class="n">source</span>
</span><span id="eliminate_subqueries-53"><a href="#eliminate_subqueries-53"><span class="linenos">53</span></a> <span class="k">for</span> <span class="n">_</span><span class="p">,</span> <span class="n">source</span> <span class="ow">in</span> <span class="n">scope</span><span class="o">.</span><span class="n">sources</span><span class="o">.</span><span class="n">items</span><span class="p">()</span>
</span><span id="eliminate_subqueries-54"><a href="#eliminate_subqueries-54"><span class="linenos">54</span></a> <span class="k">if</span> <span class="nb">isinstance</span><span class="p">(</span><span class="n">source</span><span class="p">,</span> <span class="n">exp</span><span class="o">.</span><span class="n">Table</span><span class="p">)</span>
</span><span id="eliminate_subqueries-55"><a href="#eliminate_subqueries-55"><span class="linenos">55</span></a> <span class="p">}</span>
</span><span id="eliminate_subqueries-56"><a href="#eliminate_subqueries-56"><span class="linenos">56</span></a> <span class="p">)</span>
</span><span id="eliminate_subqueries-57"><a href="#eliminate_subqueries-57"><span class="linenos">57</span></a>
</span><span id="eliminate_subqueries-58"><a href="#eliminate_subqueries-58"><span class="linenos">58</span></a> <span class="c1"># Map of Expression->alias</span>
</span><span id="eliminate_subqueries-59"><a href="#eliminate_subqueries-59"><span class="linenos">59</span></a> <span class="c1"># Existing CTES in the root expression. We'll use this for deduplication.</span>
</span><span id="eliminate_subqueries-60"><a href="#eliminate_subqueries-60"><span class="linenos">60</span></a> <span class="n">existing_ctes</span> <span class="o">=</span> <span class="p">{}</span>
</span><span id="eliminate_subqueries-61"><a href="#eliminate_subqueries-61"><span class="linenos">61</span></a>
</span><span id="eliminate_subqueries-62"><a href="#eliminate_subqueries-62"><span class="linenos">62</span></a> <span class="n">with_</span> <span class="o">=</span> <span class="n">root</span><span class="o">.</span><span class="n">expression</span><span class="o">.</span><span class="n">args</span><span class="o">.</span><span class="n">get</span><span class="p">(</span><span class="s2">"with"</span><span class="p">)</span>
</span><span id="eliminate_subqueries-63"><a href="#eliminate_subqueries-63"><span class="linenos">63</span></a> <span class="n">recursive</span> <span class="o">=</span> <span class="kc">False</span>
</span><span id="eliminate_subqueries-64"><a href="#eliminate_subqueries-64"><span class="linenos">64</span></a> <span class="k">if</span> <span class="n">with_</span><span class="p">:</span>
</span><span id="eliminate_subqueries-65"><a href="#eliminate_subqueries-65"><span class="linenos">65</span></a> <span class="n">recursive</span> <span class="o">=</span> <span class="n">with_</span><span class="o">.</span><span class="n">args</span><span class="o">.</span><span class="n">get</span><span class="p">(</span><span class="s2">"recursive"</span><span class="p">)</span>
</span><span id="eliminate_subqueries-66"><a href="#eliminate_subqueries-66"><span class="linenos">66</span></a> <span class="k">for</span> <span class="n">cte</span> <span class="ow">in</span> <span class="n">with_</span><span class="o">.</span><span class="n">expressions</span><span class="p">:</span>
</span><span id="eliminate_subqueries-67"><a href="#eliminate_subqueries-67"><span class="linenos">67</span></a> <span class="n">existing_ctes</span><span class="p">[</span><span class="n">cte</span><span class="o">.</span><span class="n">this</span><span class="p">]</span> <span class="o">=</span> <span class="n">cte</span><span class="o">.</span><span class="n">alias</span>
</span><span id="eliminate_subqueries-68"><a href="#eliminate_subqueries-68"><span class="linenos">68</span></a> <span class="n">new_ctes</span> <span class="o">=</span> <span class="p">[]</span>
</span><span id="eliminate_subqueries-69"><a href="#eliminate_subqueries-69"><span class="linenos">69</span></a>
</span><span id="eliminate_subqueries-70"><a href="#eliminate_subqueries-70"><span class="linenos">70</span></a> <span class="c1"># We're adding more CTEs, but we want to maintain the DAG order.</span>
</span><span id="eliminate_subqueries-71"><a href="#eliminate_subqueries-71"><span class="linenos">71</span></a> <span class="c1"># Derived tables within an existing CTE need to come before the existing CTE.</span>
</span><span id="eliminate_subqueries-72"><a href="#eliminate_subqueries-72"><span class="linenos">72</span></a> <span class="k">for</span> <span class="n">cte_scope</span> <span class="ow">in</span> <span class="n">root</span><span class="o">.</span><span class="n">cte_scopes</span><span class="p">:</span>
</span><span id="eliminate_subqueries-73"><a href="#eliminate_subqueries-73"><span class="linenos">73</span></a> <span class="c1"># Append all the new CTEs from this existing CTE</span>
</span><span id="eliminate_subqueries-74"><a href="#eliminate_subqueries-74"><span class="linenos">74</span></a> <span class="k">for</span> <span class="n">scope</span> <span class="ow">in</span> <span class="n">cte_scope</span><span class="o">.</span><span class="n">traverse</span><span class="p">():</span>
</span><span id="eliminate_subqueries-75"><a href="#eliminate_subqueries-75"><span class="linenos">75</span></a> <span class="k">if</span> <span class="n">scope</span> <span class="ow">is</span> <span class="n">cte_scope</span><span class="p">:</span>
</span><span id="eliminate_subqueries-76"><a href="#eliminate_subqueries-76"><span class="linenos">76</span></a> <span class="c1"># Don't try to eliminate this CTE itself</span>
</span><span id="eliminate_subqueries-77"><a href="#eliminate_subqueries-77"><span class="linenos">77</span></a> <span class="k">continue</span>
</span><span id="eliminate_subqueries-78"><a href="#eliminate_subqueries-78"><span class="linenos">78</span></a> <span class="n">new_cte</span> <span class="o">=</span> <span class="n">_eliminate</span><span class="p">(</span><span class="n">scope</span><span class="p">,</span> <span class="n">existing_ctes</span><span class="p">,</span> <span class="n">taken</span><span class="p">)</span>
</span><span id="eliminate_subqueries-79"><a href="#eliminate_subqueries-79"><span class="linenos">79</span></a> <span class="k">if</span> <span class="n">new_cte</span><span class="p">:</span>
</span><span id="eliminate_subqueries-80"><a href="#eliminate_subqueries-80"><span class="linenos">80</span></a> <span class="n">new_ctes</span><span class="o">.</span><span class="n">append</span><span class="p">(</span><span class="n">new_cte</span><span class="p">)</span>
</span><span id="eliminate_subqueries-81"><a href="#eliminate_subqueries-81"><span class="linenos">81</span></a>
</span><span id="eliminate_subqueries-82"><a href="#eliminate_subqueries-82"><span class="linenos">82</span></a> <span class="c1"># Append the existing CTE itself</span>
</span><span id="eliminate_subqueries-83"><a href="#eliminate_subqueries-83"><span class="linenos">83</span></a> <span class="n">new_ctes</span><span class="o">.</span><span class="n">append</span><span class="p">(</span><span class="n">cte_scope</span><span class="o">.</span><span class="n">expression</span><span class="o">.</span><span class="n">parent</span><span class="p">)</span>
</span><span id="eliminate_subqueries-84"><a href="#eliminate_subqueries-84"><span class="linenos">84</span></a>
</span><span id="eliminate_subqueries-85"><a href="#eliminate_subqueries-85"><span class="linenos">85</span></a> <span class="c1"># Now append the rest</span>
</span><span id="eliminate_subqueries-86"><a href="#eliminate_subqueries-86"><span class="linenos">86</span></a> <span class="k">for</span> <span class="n">scope</span> <span class="ow">in</span> <span class="n">itertools</span><span class="o">.</span><span class="n">chain</span><span class="p">(</span><span class="n">root</span><span class="o">.</span><span class="n">union_scopes</span><span class="p">,</span> <span class="n">root</span><span class="o">.</span><span class="n">subquery_scopes</span><span class="p">,</span> <span class="n">root</span><span class="o">.</span><span class="n">table_scopes</span><span class="p">):</span>
</span><span id="eliminate_subqueries-87"><a href="#eliminate_subqueries-87"><span class="linenos">87</span></a> <span class="k">for</span> <span class="n">child_scope</span> <span class="ow">in</span> <span class="n">scope</span><span class="o">.</span><span class="n">traverse</span><span class="p">():</span>
</span><span id="eliminate_subqueries-88"><a href="#eliminate_subqueries-88"><span class="linenos">88</span></a> <span class="n">new_cte</span> <span class="o">=</span> <span class="n">_eliminate</span><span class="p">(</span><span class="n">child_scope</span><span class="p">,</span> <span class="n">existing_ctes</span><span class="p">,</span> <span class="n">taken</span><span class="p">)</span>
</span><span id="eliminate_subqueries-89"><a href="#eliminate_subqueries-89"><span class="linenos">89</span></a> <span class="k">if</span> <span class="n">new_cte</span><span class="p">:</span>
</span><span id="eliminate_subqueries-90"><a href="#eliminate_subqueries-90"><span class="linenos">90</span></a> <span class="n">new_ctes</span><span class="o">.</span><span class="n">append</span><span class="p">(</span><span class="n">new_cte</span><span class="p">)</span>
</span><span id="eliminate_subqueries-91"><a href="#eliminate_subqueries-91"><span class="linenos">91</span></a>
</span><span id="eliminate_subqueries-92"><a href="#eliminate_subqueries-92"><span class="linenos">92</span></a> <span class="k">if</span> <span class="n">new_ctes</span><span class="p">:</span>
</span><span id="eliminate_subqueries-93"><a href="#eliminate_subqueries-93"><span class="linenos">93</span></a> <span class="n">expression</span><span class="o">.</span><span class="n">set</span><span class="p">(</span><span class="s2">"with"</span><span class="p">,</span> <span class="n">exp</span><span class="o">.</span><span class="n">With</span><span class="p">(</span><span class="n">expressions</span><span class="o">=</span><span class="n">new_ctes</span><span class="p">,</span> <span class="n">recursive</span><span class="o">=</span><span class="n">recursive</span><span class="p">))</span>
</span><span id="eliminate_subqueries-94"><a href="#eliminate_subqueries-94"><span class="linenos">94</span></a>
</span><span id="eliminate_subqueries-95"><a href="#eliminate_subqueries-95"><span class="linenos">95</span></a> <span class="k">return</span> <span class="n">expression</span>
</span></pre></div>
<div class="docstring"><p>Rewrite derived tables as CTES, deduplicating if possible.</p>
<h6 id="example">Example:</h6>
<blockquote>
<div class="pdoc-code codehilite">
<pre><span></span><code><span class="gp">>>> </span><span class="kn">import</span> <span class="nn">sqlglot</span>
<span class="gp">>>> </span><span class="n">expression</span> <span class="o">=</span> <span class="n"><a href="../../sqlglot.html#parse_one">sqlglot.parse_one</a></span><span class="p">(</span><span class="s2">"SELECT a FROM (SELECT * FROM x) AS y"</span><span class="p">)</span>
<span class="gp">>>> </span><span class="n">eliminate_subqueries</span><span class="p">(</span><span class="n">expression</span><span class="p">)</span><span class="o">.</span><span class="n">sql</span><span class="p">()</span>
<span class="go">'WITH y AS (SELECT * FROM x) SELECT a FROM y AS y'</span>
</code></pre>
</div>
</blockquote>
<h6 id="this-also-deduplicates-common-subqueries">This also deduplicates common subqueries:</h6>
<blockquote>
<div class="pdoc-code codehilite">
<pre><span></span><code><span class="gp">>>> </span><span class="n">expression</span> <span class="o">=</span> <span class="n"><a href="../../sqlglot.html#parse_one">sqlglot.parse_one</a></span><span class="p">(</span><span class="s2">"SELECT a FROM (SELECT * FROM x) AS y CROSS JOIN (SELECT * FROM x) AS z"</span><span class="p">)</span>
<span class="gp">>>> </span><span class="n">eliminate_subqueries</span><span class="p">(</span><span class="n">expression</span><span class="p">)</span><span class="o">.</span><span class="n">sql</span><span class="p">()</span>
<span class="go">'WITH y AS (SELECT * FROM x) SELECT a FROM y AS y CROSS JOIN y AS z'</span>
</code></pre>
</div>
</blockquote>
<h6 id="arguments">Arguments:</h6>
<ul>
<li><strong>expression (sqlglot.Expression):</strong> expression</li>
</ul>
<h6 id="returns">Returns:</h6>
<blockquote>
<p>sqlglot.Expression: expression</p>
</blockquote>
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