Data update
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Ingy döt Net
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10248 changed files with 63654 additions and 6775 deletions
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An [[wp:Join_(SQL)#Inner_join|inner join]] is an operation that combines two data tables into one table, based on matching column values. The simplest way of implementing this operation is the [[wp:Nested loop join|nested loop join]] algorithm, but a more scalable alternative is the [[wp:hash join|hash join]] algorithm.
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{{task heading}}
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;Task
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Implement the "hash join" algorithm, and demonstrate that it passes the test-case listed below.
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You should represent the tables as data structures that feel natural in your programming language.
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{{task heading|Guidance}}
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;Guidance
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The "hash join" algorithm consists of two steps:
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@ -33,7 +33,7 @@ In pseudo-code, the algorithm could be expressed as follows:
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'''let''' ''c'' = the concatenation of row ''a'' and row ''b''
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'''place''' row ''c'' in table ''C''
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{{task heading|Test-case}}
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;Test case
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{| class="wikitable"
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@ -1,37 +1,28 @@
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(phixonline)-->
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<span style="color: #008080;">with</span> <span style="color: #008080;">javascript_semantics</span>
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<span style="color: #008080;">constant</span> <span style="color: #000000;">A</span> <span style="color: #0000FF;">=</span> <span style="color: #0000FF;">{{</span><span style="color: #000000;">27</span><span style="color: #0000FF;">,</span><span style="color: #008000;">"Jonah"</span><span style="color: #0000FF;">},</span>
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<span style="color: #0000FF;">{</span><span style="color: #000000;">18</span><span style="color: #0000FF;">,</span><span style="color: #008000;">"Alan"</span><span style="color: #0000FF;">},</span>
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<span style="color: #0000FF;">{</span><span style="color: #000000;">28</span><span style="color: #0000FF;">,</span><span style="color: #008000;">"Glory"</span><span style="color: #0000FF;">},</span>
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<span style="color: #0000FF;">{</span><span style="color: #000000;">18</span><span style="color: #0000FF;">,</span><span style="color: #008000;">"Popeye"</span><span style="color: #0000FF;">},</span>
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<span style="color: #0000FF;">{</span><span style="color: #000000;">28</span><span style="color: #0000FF;">,</span><span style="color: #008000;">"Alan"</span><span style="color: #0000FF;">}},</span>
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<span style="color: #000000;">B</span> <span style="color: #0000FF;">=</span> <span style="color: #0000FF;">{{</span><span style="color: #008000;">"Jonah"</span><span style="color: #0000FF;">,</span><span style="color: #008000;">"Whales"</span><span style="color: #0000FF;">},</span>
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<span style="color: #0000FF;">{</span><span style="color: #008000;">"Jonah"</span><span style="color: #0000FF;">,</span><span style="color: #008000;">"Spiders"</span><span style="color: #0000FF;">},</span>
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<span style="color: #0000FF;">{</span><span style="color: #008000;">"Alan"</span><span style="color: #0000FF;">,</span> <span style="color: #008000;">"Ghosts"</span><span style="color: #0000FF;">},</span>
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<span style="color: #0000FF;">{</span><span style="color: #008000;">"Alan"</span><span style="color: #0000FF;">,</span> <span style="color: #008000;">"Zombies"</span><span style="color: #0000FF;">},</span>
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<span style="color: #0000FF;">{</span><span style="color: #008000;">"Glory"</span><span style="color: #0000FF;">,</span><span style="color: #008000;">"Buffy"</span><span style="color: #0000FF;">}},</span>
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<span style="color: #000000;">jA</span> <span style="color: #0000FF;">=</span> <span style="color: #000000;">2</span><span style="color: #0000FF;">,</span>
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<span style="color: #000000;">jB</span> <span style="color: #0000FF;">=</span> <span style="color: #000000;">1</span><span style="color: #0000FF;">,</span>
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<span style="color: #000000;">MB</span> <span style="color: #0000FF;">=</span> <span style="color: #7060A8;">new_dict</span><span style="color: #0000FF;">()</span>
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<span style="color: #004080;">sequence</span> <span style="color: #000000;">C</span> <span style="color: #0000FF;">=</span> <span style="color: #0000FF;">{}</span>
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<span style="color: #008080;">for</span> <span style="color: #000000;">i</span><span style="color: #0000FF;">=</span><span style="color: #000000;">1</span> <span style="color: #008080;">to</span> <span style="color: #7060A8;">length</span><span style="color: #0000FF;">(</span><span style="color: #000000;">B</span><span style="color: #0000FF;">)</span> <span style="color: #008080;">do</span>
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<span style="color: #004080;">object</span> <span style="color: #000000;">key</span> <span style="color: #0000FF;">=</span> <span style="color: #000000;">B</span><span style="color: #0000FF;">[</span><span style="color: #000000;">i</span><span style="color: #0000FF;">][</span><span style="color: #000000;">jB</span><span style="color: #0000FF;">]</span>
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<span style="color: #004080;">object</span> <span style="color: #000000;">data</span> <span style="color: #0000FF;">=</span> <span style="color: #7060A8;">getd</span><span style="color: #0000FF;">(</span><span style="color: #000000;">key</span><span style="color: #0000FF;">,</span><span style="color: #000000;">MB</span><span style="color: #0000FF;">)</span>
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<span style="color: #008080;">if</span> <span style="color: #000000;">data</span><span style="color: #0000FF;">=</span><span style="color: #000000;">0</span> <span style="color: #008080;">then</span>
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<span style="color: #000000;">data</span> <span style="color: #0000FF;">=</span> <span style="color: #0000FF;">{</span><span style="color: #000000;">B</span><span style="color: #0000FF;">[</span><span style="color: #000000;">i</span><span style="color: #0000FF;">]}</span>
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<span style="color: #008080;">else</span>
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<span style="color: #000000;">data</span> <span style="color: #0000FF;">=</span> <span style="color: #7060A8;">append</span><span style="color: #0000FF;">(</span><span style="color: #000000;">data</span><span style="color: #0000FF;">,</span><span style="color: #000000;">B</span><span style="color: #0000FF;">[</span><span style="color: #000000;">i</span><span style="color: #0000FF;">])</span>
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<span style="color: #008080;">end</span> <span style="color: #008080;">if</span>
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<span style="color: #7060A8;">putd</span><span style="color: #0000FF;">(</span><span style="color: #000000;">key</span><span style="color: #0000FF;">,</span><span style="color: #000000;">data</span><span style="color: #0000FF;">,</span><span style="color: #000000;">MB</span><span style="color: #0000FF;">)</span>
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<span style="color: #008080;">end</span> <span style="color: #008080;">for</span>
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<span style="color: #008080;">for</span> <span style="color: #000000;">i</span><span style="color: #0000FF;">=</span><span style="color: #000000;">1</span> <span style="color: #008080;">to</span> <span style="color: #7060A8;">length</span><span style="color: #0000FF;">(</span><span style="color: #000000;">A</span><span style="color: #0000FF;">)</span> <span style="color: #008080;">do</span>
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<span style="color: #004080;">object</span> <span style="color: #000000;">data</span> <span style="color: #0000FF;">=</span> <span style="color: #7060A8;">getd</span><span style="color: #0000FF;">(</span><span style="color: #000000;">A</span><span style="color: #0000FF;">[</span><span style="color: #000000;">i</span><span style="color: #0000FF;">][</span><span style="color: #000000;">jA</span><span style="color: #0000FF;">],</span><span style="color: #000000;">MB</span><span style="color: #0000FF;">)</span>
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<span style="color: #008080;">if</span> <span style="color: #004080;">sequence</span><span style="color: #0000FF;">(</span><span style="color: #000000;">data</span><span style="color: #0000FF;">)</span> <span style="color: #008080;">then</span>
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<span style="color: #008080;">for</span> <span style="color: #000000;">j</span><span style="color: #0000FF;">=</span><span style="color: #000000;">1</span> <span style="color: #008080;">to</span> <span style="color: #7060A8;">length</span><span style="color: #0000FF;">(</span><span style="color: #000000;">data</span><span style="color: #0000FF;">)</span> <span style="color: #008080;">do</span>
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<span style="color: #000000;">C</span> <span style="color: #0000FF;">=</span> <span style="color: #7060A8;">append</span><span style="color: #0000FF;">(</span><span style="color: #000000;">C</span><span style="color: #0000FF;">,{</span><span style="color: #000000;">A</span><span style="color: #0000FF;">[</span><span style="color: #000000;">i</span><span style="color: #0000FF;">],</span><span style="color: #000000;">data</span><span style="color: #0000FF;">[</span><span style="color: #000000;">j</span><span style="color: #0000FF;">]})</span>
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<span style="color: #008080;">end</span> <span style="color: #008080;">for</span>
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<span style="color: #008080;">end</span> <span style="color: #008080;">if</span>
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<span style="color: #008080;">end</span> <span style="color: #008080;">for</span>
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<span style="color: #7060A8;">destroy_dict</span><span style="color: #0000FF;">(</span><span style="color: #000000;">MB</span><span style="color: #0000FF;">)</span>
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<span style="color: #7060A8;">pp</span><span style="color: #0000FF;">(</span><span style="color: #000000;">C</span><span style="color: #0000FF;">,{</span><span style="color: #004600;">pp_Nest</span><span style="color: #0000FF;">,</span><span style="color: #000000;">1</span><span style="color: #0000FF;">})</span>
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<!--
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with javascript_semantics
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constant A = {{27,"Jonah"},
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{18,"Alan"},
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{28,"Glory"},
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{18,"Popeye"},
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{28,"Alan"}},
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B = {{"Jonah","Whales"},
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{"Jonah","Spiders"},
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{"Alan", "Ghosts"},
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{"Alan", "Zombies"},
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{"Glory","Buffy"}},
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jA = 2,
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jB = 1,
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MB = new_dict()
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sequence C = {}
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for b in B do
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object key = b[jB],
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data = getdd(key,{},MB)
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data = append(deep_copy(data),b)
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putd(key,data,MB)
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end for
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for a in A do
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for d in getdd(a[jA],{},MB) do
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C = append(C,{a,d})
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end for
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end for
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destroy_dict(MB)
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pp(C,{pp_Nest,1})
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